Systems, methods and tools for inspection of composite strength members - Patents.com

Abstract

To provide systems, methods and tools for the interrogation of fiber-reinforced composite strength members to assess the structural integrity of the strength members.SOLUTION: Systems and methods utilize the transmission of light through optical fibers that are embedded along the overall length of strength members. The inability to detect light through one or more of the optical fibers may be an indication that the structural integrity of the strength member is compromised. The systems and methods may be implemented without great difficulty and may be implemented at any time in the life cycle of the strength member, from production through installation. The systems and methods have particular applicability to bare overhead electrical cables that include a fiber-reinforced strength member.SELECTED DRAWING: Figure 3A-3C

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to the field of fiber reinforced composite strength members, and in particular to the field of structural integrity testing of such fiber reinforced composite strength members. [Background technology]

[0002] Fiber-reinforced composite strength members have a relatively high strength-to-weight ratio and other desirable properties that make them advantageous for use in a variety of structural applications. For example, many elongated fiber-reinforced composite strength members are used as tensile members in structures such as bridges and railroad messenger wires, replacing traditionally used materials such as steel.

[0003] One such application of fiber-reinforced composite strength members that has recently emerged is their use in bare overhead electrical cables for power transmission and distribution. Such electrical cables typically include a plurality of conductive metal strands wound around and supported by a central strength member. Traditionally, the strength members have been made of steel. Recently, fiber-reinforced composite materials have been utilized for the strength members. Such composite materials offer significant advantages over steel, including reduced weight, reduced size (allowing for the use of conductors with larger cross-sectional areas), reduced thermal sag, and many other advantages. One example of an overhead electrical cable having such fiber-reinforced strength members is the ACCC® bare overhead electrical cable available from CTC Global Corporation, Irvine, California, USA. See, for example, U.S. Patent No. 6,399,633, which is incorporated herein by reference in its entirety.

[0004] Unlike most metallic materials, fiber-reinforced composite materials typically have low ductility. As a result, concerns may arise that fiber-reinforced composite strength members may be structurally damaged (e.g., break) during manufacture, handling, and / or installation of the strength members and / or electrical cables. Small breaks in the strength members may be difficult to detect using conventional methods. This is especially true for overhead electrical cables due to the extreme lengths of the cables and the fact that the strength members are not visible after the conductive strands are wrapped around them.

[0005] Methods and systems have been proposed for monitoring the condition of fiber-reinforced strength members while the strength members are in use. For example, it has been proposed that the temperature and strain of strength members in overhead electrical cables could be monitored during use using complex techniques such as optical time domain reflectometry (OTDR). However, such systems and methods require complex equipment, require the use of a coherent light source (e.g., a laser), and require precise alignment of the coherent light source with the optical fiber attached to the strength members, all of which are difficult to implement in the field, for example in outdoor environments where electrical transmission and distribution lines are installed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 7,368,162 Summary of the Invention

[0007] Disclosed herein are systems, methods, components, and tools that allow for inspection of fiber reinforced composite strength members to determine whether the composite strength members are structurally intact, e.g., to detect the presence of defects, such as breaks, in the strength members. The systems, methods, components, and tools allow for relatively simple and low-cost inspection of the strength members during the manufacturing process, installation, and / or after installation.

[0008] The systems, methods, components, and tools disclosed herein include, but are not limited to, the following: (i) A system for detecting defects in fiber-reinforced composite strength members.

[0009] (ii) A method for detecting defects in fiber-reinforced composite strength members. (iii) A method for preparing fiber-reinforced composite strength elements for inspection using a light source. (iv) Elongated fiber reinforced composite strength members including optical fibers.

[0010] (v) A device for transmitting light to an end of an optical fiber embedded in an elongated structural member. (vi) A device for detecting light emanating from the end of an optical fiber embedded in the elongated structural member.

[0011] (vii) Cutting and polishing tools. (viii) A method of making an elongated fiber reinforced composite strength element configured for use in a tensile strength member.

[0012] Thus, in one embodiment, a system configured to detect defects in a fiber reinforced composite strength member is disclosed. The system includes a fiber reinforced composite strength member, the strength member including at least a first strength element. The first strength element includes a bonding matrix, a plurality of reinforcing fibers operatively arranged within the bonding matrix to form a fiber reinforced composite, and at least a first optical fiber embedded within the fiber reinforced composite and extending from a first end of the fiber reinforced composite to a second end of the fiber reinforced composite. An optical transmission device is operatively connected to the first end of the strength member, the optical transmission device including a light source configured to transmit light having a wavelength of at least about 300 nm and not greater than about 1700 nm through a first end of the first optical fiber. An optical detection device is operatively connected to the second end of the strength member, the optical detection device including a light detector configured to detect light from the optical transmission device that has passed through the second end of the first optical fiber.

[0013] The foregoing systems may be characterized as having feature refinements and / or additional features that may be implemented singly or in any combination. In one feature, the light source is configured to emit light having a dominant wavelength in the infrared region. In one refinement, the light source is configured to emit light having a dominant wavelength of at least about 800 nm. In another refinement, the light source is configured to emit light having a dominant wavelength of about 1000 nm or less.

[0014] In another feature, the strength element includes at least a second optical fiber embedded in the fiber-reinforced composite and extending the entire length of the fiber-reinforced composite. In one refinement, the strength element includes at least a third optical fiber embedded in the fiber-reinforced composite and extending the entire length of the fiber-reinforced composite. In another refinement, the strength element includes at least a fourth optical fiber embedded in the fiber-reinforced composite and extending the entire length of the fiber-reinforced composite.

[0015] In another feature, the electrical cable has a length of at least about 100 meters. In yet another feature, the electrical cable has a length of about 3500 meters or less. In one feature, electrical conductors are disposed about and supported by strength members to form the electrical cable.

[0016] In another feature, the first optical fiber is a single mode optical fiber. In another feature, the light source includes a light emitting diode (LED). In another feature, the light detection device includes a concave lens disposed between the end of the composite strength member and the light sensor and configured to focus the transmitted light onto the light sensor. In another refinement, the light sensor is selected from a CCD sensor and a CMOS sensor.

[0017] In another embodiment, a method is disclosed for probing a fiber reinforced composite strength member. The strength member includes at least a first strength element, the strength element including a bonding matrix and a plurality of reinforcing fibers operatively arranged within the bonding matrix to form a fiber reinforced composite. At least a first optical fiber is embedded in the fiber reinforced composite and extends the entire length of the fiber reinforced composite. The method includes operably attaching an optical transmission device to a first end of the strength member, operably attaching an optical detection device to a second end of the strength member, transmitting light from the optical transmission device through the first optical fiber toward the optical detection device, where the transmitted light is incoherent and detecting the presence of the incoherent transmitted light by the optical detection device.

[0018] The foregoing methods may be characterized as having refinements and / or additional method steps that may be implemented singly or in any combination. In one feature, the transmitted light has a wavelength in the infrared region. In one refinement, the transmitted light has a dominant wavelength of at least about 800 nm. In another refinement, the transmitted light has a dominant wavelength of about 1000 nm or less. In another feature, the first strength element includes at least a second optical fiber embedded in the fiber-reinforced composite and extending the entire length of the fiber-reinforced composite, and the transmitting step transmits the light through the second optical fiber. In another refinement, the strength element includes at least a third optical fiber embedded in the fiber-reinforced composite and extending the entire length of the fiber-reinforced composite, and the transmitting step transmits the light through the third optical fiber. In another refinement, the strength element includes at least a fourth optical fiber embedded in the fiber-reinforced composite and extending the entire length of the fiber-reinforced composite, and the transmitting step transmits the light through the fourth optical fiber.

[0019] In another feature, the composite strength member has a length of at least about 500 meters. In another refinement, the composite strength member has a length of at least about 3500 meters. In another feature, the composite strength member has a length of about 7500 meters or less. In another feature, the composite strength member is wound on a spool during the steps of transmitting light and detecting light. In another feature, the method includes stress testing the composite strength element prior to the steps of transmitting light and detecting light.

[0020] In another feature, the conductors are stranded around the composite strength members to form the overhead electrical cable. In one refinement, the steps of transmitting light and detecting light are performed after stranding the conductors around the composite strength members and prior to installation of the overhead electrical cable on the support tower. In another refinement, the steps of transmitting light and detecting light are performed after installation of the overhead electrical cable on the support tower.

[0021] In another feature, the optical fiber is a single mode optical fiber. In another feature, the transmitting step includes energizing a light emitting diode (LED). In one refinement, the transmitting step includes mechanically rotating the LED while transmitting the light. In another refinement, the LED is rotated at a speed of at least about 5 rpm.

[0022] In another feature, an index matching material is applied to the first end of the strength member to facilitate the transmission of light into the optical fiber. Another embodiment of the present disclosure relates to a method of making a fiber-reinforced composite strength element for inspection with a light source, the fiber-reinforced composite including a bonding matrix and a plurality of reinforcing fibers disposed within the bonding matrix, and at least a first optical fiber disposed within the fiber-reinforced composite, the first optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite. The method includes cutting the elongated fiber-reinforced composite proximate to a first end of the elongated fiber-reinforced composite to form a substantially flat first cut end surface. The method also includes polishing the first cut end surface to form a polished first end surface, the polished first end surface including the fiber-reinforced composite and a first end of the optical fiber. The resulting fiber-reinforced composite strength element is configured to be inspected with an incoherent light source.

[0023] The foregoing methods may be characterized as having refinements and / or additional steps, which may be implemented singly or in any combination. In one refinement, the method includes cutting the fiber-reinforced composite proximate a second end of the fiber-reinforced composite to form a substantially flat second cut end surface, and polishing the second cut end surface to form a polished second end surface, the polished second end surface including the fiber-reinforced composite and the second end of the first optical fiber.

[0024] In another aspect, the fiber reinforced composite strength element has a length of at least about 100 meters. In yet another aspect, the fiber reinforced composite strength element has a length of no more than about 7500 meters. In another feature, the step or steps of cutting the fiber-reinforced composite include cutting with a powered gritted cutting edge. In one refinement, the gritted cutting edge includes abrasive grains having an abrasive grain size of at least about 30 μm. In another refinement, the gritted cutting edge is rotated by a motor during the cutting step. In another refinement, the step includes fixing a first end of the fiber-reinforced composite at least during the cutting step such that the first end is disposed substantially perpendicular to the cutting edge during the cutting step. In another refinement, the grinding step includes grinding the first cut end surface with an abrasive grinding surface. In yet another refinement, the abrasive grinding surface includes abrasive grains having an abrasive grain size not coarser than about 25 μm. In another refinement, the step includes cooling the first end of the elongated fiber-reinforced composite before and / or during the grinding step.

[0025] In another embodiment, an elongated fiber reinforced composite strength member is disclosed. The strength member includes at least a first fiber reinforced composite strength element having a longitudinal central axis. The strength element includes a bonding matrix, a plurality of reinforcing fibers disposed within the bonding matrix to form a fiber reinforced composite, and at least a first elongated continuous optical fiber embedded within the fiber reinforced composite and extending from a first end of the strength element to a second end of the strength element. At least the first end of the strength element includes a first end face, the first end face includes a fiber reinforced composite, and the first optical fiber does not extend beyond the first end face of the fiber reinforced composite.

[0026] The strength members described above may be characterized as having feature refinements and / or additional features, which may be implemented singly or in any combination. In one feature, the second end of the strength element includes a second end face, and the first optical fiber does not extend beyond the second end face of the fiber-reinforced composite.

[0027] In another feature, the strength element includes at least a second elongated continuous optical fiber embedded within the fiber-reinforced composite, the second optical fiber not extending beyond a first end surface of the fiber-reinforced composite. In one refinement, the strength element includes at least a third elongated continuous optical fiber disposed within the fiber-reinforced composite, the third optical fiber not extending beyond a first end surface of the fiber-reinforced composite. In another refinement, the strength element includes at least a fourth elongated continuous optical fiber disposed within the fiber-reinforced composite, the fourth optical fiber not extending beyond a first end surface of the fiber-reinforced composite. In another refinement, the optical fibers are concentrically disposed about a central longitudinal axis of the strength element. In yet another refinement, the central longitudinal axis of the strength element is free of optical fibers.

[0028] In one feature, the optical fiber(s) are single mode optical fibers. In another feature, the optical fiber(s) are glass optical fibers. In one refinement, the glass optical fiber(s) include a transmissive glass core and a single polymer coating surrounding the transmissive glass core. In another refinement, the single polymer coating has an elastic modulus of at least about 1000 MPa.

[0029] In one feature, the strength members have a length of at least about 100 meters. In one refinement, the strength members have a length of at least about 3500 meters. In another feature, the strength members have a length of about 7500 meters or less. In another feature, the strength members are wound on spools.

[0030] In another feature, the strength members have a substantially circular cross-section. In one refinement, the strength members have a diameter of at least about 1.0 mm. In another refinement, the strength members have a diameter of about 20 mm or less. In another feature, the reinforcing fibers include longitudinally extending carbon fibers. In one refinement, the strength members further include an insulating layer surrounding the carbon fibers. In another refinement, the insulating layer includes glass fibers. In another refinement, the optical fiber(s) are disposed between the carbon fibers and the insulating layer.

[0031] In one aspect, the strength members have a rated tensile strength of at least about 1900 MPa. In another aspect, the strength members have a rated tensile strength of at least about 30×10 -6 / °C or less. In another feature, the first end surface of the fiber-reinforced composite is a polished surface. In one refinement, the second end surface of the fiber-reinforced composite is a polished surface. In yet another refinement, the first end surface is substantially perpendicular to the central longitudinal axis of the strength member. In another refinement, the first end of the first optical fiber is substantially coplanar with the first end surface of the fiber-reinforced composite.

[0032] In one aspect, the strength member includes a single strength element. In another aspect, the strength member includes a plurality of strength elements. In another aspect, an overhead electrical cable is disclosed that includes a strength member according to any of the preceding embodiments, including any of the features and refinements, and a conductive layer surrounding the strength member. In one refinement, the conductive layer includes a plurality of conductive strands disposed about the strength member.

[0033] In another embodiment, a device for transmitting light to an end of an optical fiber embedded in an elongated structural member is disclosed. The device includes a substantially rigid structure and a bore disposed at least partially through the structure, the bore having an opening at a first end of the bore, the opening and the bore configured to receive an end of an elongated structural member having at least a first optical fiber embedded throughout the length of the structural member. A light source is disposed at least partially within the structure and proximate a second end of the bore, the light source configured to transmit light into the bore and toward the end of the elongated structural member when the elongated member is disposed within the first end of the bore. A power source is operably attached to the light source.

[0034] The foregoing devices may be characterized as having feature refinements and / or additional features, which may be implemented singly or in any combination. In one feature, the light source is an incoherent light source. In one refinement, the light source includes a light emitting diode (LED). In another refinement, the LED is configured to emit light in a wavelength range of at least about 300 nm and up to about 1000 nm. In another refinement, the LED is configured to emit light in a wavelength range of at least about 800 nm and up to about 900 nm.

[0035] In another feature, a motor is operatively connected to the light source and configured to move the light source as the light source transmits light into the bore. In one refinement, the motor is configured to rotate the light source about a central axis of the light source.

[0036] In another feature, a stop element is provided to maintain a distance between the light source and an end of the structural member when the structural member is disposed in the first end of the bore. In one refinement, the stop element includes a shoulder disposed in the bore configured to prevent movement of the structural member past the shoulder in a direction toward the light source. In one refinement, the stop element is configured to maintain a distance between the end of the structural member and the light source of at least about 0.1 mm and no more than about 150 mm. In one feature, the rigid structure is comprised of a metal. In one refinement, the metal includes aluminum.

[0037] Another embodiment according to the present disclosure is a device for detecting light emanating from an end of an optical fiber embedded in an elongated structural member. The device includes a substantially rigid structure and a bore disposed at least partially through the structure, the bore having an opening at a first end of the bore. The opening and the bore are configured to receive an end of an elongated structural member having at least a first optical fiber embedded throughout the length of the structural member. A photodetector is disposed within the structure proximate a second end of the bore. The photodetector is configured to receive and detect light from the optical fiber when the elongated member is disposed within the first end of the bore. A power source is operably attached to the photodetector.

[0038] The aforementioned devices may be characterized as having feature refinements and / or additional features that may be implemented singly or in any combination. In one feature, the light detector is selected from a CCD sensor and a CMOS sensor. In another feature, the device includes a light blocking element disposed at a first end of the bore and configured to seal around the structural member when the structural member is disposed within the bore. In one refinement, the light blocking element includes an elastomeric material.

[0039] In another feature, the device includes a stop element configured to maintain a distance between the photodetector and an end of the structural member when the structural member is disposed within the first end of the bore. In one refinement, the stop element includes a shoulder disposed within the bore, the shoulder configured to prevent movement of the structural member past the shoulder toward the photodetector. In another refinement, the stop element is configured to maintain a distance between the end of the structural member and the photodetector of at least about 5 mm and no more than about 300 mm.

[0040] In another feature, the device includes a lens configured to focus light emanating from the optical fiber onto the photodetector. In another feature, the rigid structure is made of a metal. In one refinement, the metal includes aluminum.

[0041] In another embodiment, a cutting and polishing tool is disclosed. The tool includes a planar body, the planar body including a cutting blade disposed along at least one edge of the planar body and an abrasive surface covering at least a portion of the planar body. An alignment member is operatively associated with the planar body and configured to operatively align an elongated structural member having a longitudinal axis with the planar body such that the cutting blade of the planar body is configured to move and cut the elongated structural member substantially perpendicular to the longitudinal axis to form a cut surface. The abrasive surface is configured to polish the cut surface as the cutting blade moves through and cuts the elongated structural member.

[0042] The aforementioned tools for cutting and polishing may be characterized as having feature refinements and / or additional features that may be implemented alone or in any combination. In one feature, the planar body is substantially circular. In one refinement, a motor is operatively connected to the planar body and configured to rotate the planar body about a central axis of the planar body. In another refinement, the cutting blade includes a plurality of cutting teeth. In yet another refinement, the cutting blade includes an abrasive surface. In yet another refinement, the abrasive surface includes abrasive grains having a size of at least about 35 μm. In another feature, the polishing surface includes abrasive polishing grains of an abrasive material. In one refinement, the abrasive grains have a size of about 25 μm or less. In another refinement, the polishing surface is located at least about 0.1 mm and about 1.2 mm or less above the surface of the planar body. In another feature, the actuation mechanism is configured to urge the polishing surface toward an end of the elongated structure. In one refinement, the actuation mechanism includes a spring.

[0043] In another feature, a battery powers the movement mechanism of the planar body. In one refinement, the battery has a voltage of about 18 volts or less. In another refinement, the tool is a handheld tool with a gripping member for gripping and freely manipulating the tool. In one refinement, the tool includes a capture mechanism configured for capture of dust from the cutting and grinding steps.

[0044] According to another embodiment, a method of making an elongated fiber-reinforced composite strength element configured for use in a tensile strength member is disclosed. The method includes forming an elongated fiber-reinforced composite having a longitudinal central axis, the fiber-reinforced composite including a bonding matrix and a plurality of reinforcing fibers disposed within the bonding matrix. During the step of forming the fiber-reinforced composite, at least a first optical fiber is embedded in the fiber-reinforced composite, the first optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite. The fiber-reinforced composite is cut proximate to the first end of the fiber-reinforced composite, the cut forming a substantially flat first cut end surface. The first cut end surface is then polished to form an elongated fiber-reinforced composite strength element having a polished first end surface, the polished first end surface including the fiber-reinforced composite and the first end of the optical fiber.

[0045] The foregoing methods may be characterized as having improvements and / or additional steps, which may be implemented singly or in any combination. In one aspect, the method includes cutting the fiber-reinforced composite proximate a second end of the fiber-reinforced composite to form a substantially flat second cut end surface, and polishing the second cut end surface to form a polished second end surface, the polished second end surface including the fiber-reinforced composite and the second end of the first optical fiber.

[0046] In another feature, the method includes embedding at least a second optical fiber in the fiber-reinforced composite during the step of forming the fiber-reinforced composite, the second optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite. In another refinement, the method includes embedding at least a third optical fiber in the fiber-reinforced composite, the third optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite. In a further refinement, the method includes embedding at least a fourth optical fiber in the fiber-reinforced composite, the fourth optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite.

[0047] In another feature, the optical fiber is concentrically disposed about a central longitudinal axis of the strength element. In another refinement, the central longitudinal axis of the strength element is free of optical fiber. In another feature, the strength element has a length of at least about 3500 meters. In yet another feature, the strength element has a length of no more than about 7500 meters. In another feature, the method further comprises winding the fiber-reinforced composite on a spool prior to the cutting and grinding steps. In another feature, the reinforcing fibers comprise longitudinally extending carbon fibers. In another feature, forming an elongated fiber-reinforced composite and embedding the optical fiber comprises pulling the reinforcing fibers and the optical fiber(s) through a drawing device. In another refinement, the step(s) of cutting the fiber-reinforced composite comprises cutting with a powered abrasive cutting blade. In another feature, the abrasive cutting blade comprises abrasive grains having a size of at least about 30 μm. In another refinement, the powered abrasive cutting blade is rotated by a motor during the cutting step.

[0048] In another feature, the method includes securing a first end of the fiber-reinforced composite such that the first end is positioned substantially perpendicular to the cutting edge during the cutting step. In another refinement, the grinding step includes grinding the first cut end surface with an abrasive surface. In yet another refinement, the abrasive surface includes abrasive grains having an abrasive grain size of about 25 μm or less. In another feature, the method includes cooling the first end of the fiber-reinforced composite before and / or during the grinding step. [Brief description of the drawings]

[0049] [Figure 1A] FIG. 1 is a perspective view of a bare overhead electrical cable. [Figure 1B] FIG. 1 is a perspective view of a bare overhead electrical cable. [Figure 2A-2B] 1 is a cross-sectional view of a composite strength element configured for use in an overhead electrical cable; FIG. [Figure 3A-3C] 1 is a cross-sectional view of a composite strength element including an optical fiber according to an embodiment of the present disclosure. [Fig. 3D-3F]1 is a cross-sectional view of a composite strength element including an optical fiber according to an embodiment of the present disclosure. [Figure 4] FIG. 1 is a schematic diagram of a system for inspection of composite strength members according to an embodiment of the present disclosure. [Diagram 5] FIG. 1 illustrates an optical transmission device according to an embodiment of the present disclosure. [Figure 6] FIG. 1 illustrates a light detection device according to an embodiment of the present disclosure. [Figure 7A] FIG. 1 illustrates a cutting and polishing tool according to an embodiment of the present disclosure. [Figure 7B] FIG. 1 illustrates a cutting and polishing tool according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] The present disclosure relates to systems, methods, components and tools that enable probing of fiber reinforced composite strength members to determine the structural integrity of the composite strength members. As the term is used in this disclosure, a fiber-reinforced composite strength member is a fiber-reinforced composite structure used in applications such as (e.g., bare overhead electrical cables) for light weight and good mechanical properties (e.g., high tensile strength) compared to steel. A fiber-reinforced composite contains reinforcing fibers in a bonding matrix. A strength member may include a single (i.e., one or less) strength element (e.g., a piece of fiber-reinforced composite strength member) or may be composed of multiple composite strength elements combined (e.g., twisted, stranded, or otherwise bound together) to form a strength member. Thus, this disclosure may use the terms strength member and strength element interchangeably, particularly when the strength member includes a single strength element.

[0051] The systems and methods for inspection disclosed herein can incorporate strength members that are uniquely configured for use in the systems and methods, as well as for use in similar systems and methods. In one embodiment, a system and method for inspection of a fiber-reinforced composite strength member is disclosed, the composite strength member including a fiber-reinforced composite strength element having at least a first optical fiber disposed within the strength element, an optical transmission device operably connected to a first end of the strength element, and an optical sensing device operably connected to a second end of the strength element. The system and method are configured to inspect the strength member to determine whether the strength member is structurally damaged. The system and method are cost-effective and relatively simple to implement at any point throughout the manufacture and installation of the strength member.

[0052] According to the present disclosure, a fiber reinforced composite strength member may have one or more properties that enable inspection of the strength member in inspection systems and methods, although the properties of the fiber reinforced composite strength member disclosed herein may enable its use in other systems and other methods.

[0053] The strength members can be utilized in a variety of structural applications, particularly as tensile strength members. In one particular embodiment, the elongated fiber-reinforced composite strength members are configured for use in overhead electrical cables, such as, for example, bare overhead electrical cables. As discussed above, overhead electrical cables for the transmission and / or distribution of electricity typically include a central strength member and electrical conductors disposed around and supported by the strength members. While strength members have traditionally been manufactured from steel, such steel strength members are increasingly being replaced by strength members manufactured from composite materials, particularly fiber-reinforced composite materials, which offer many distinct advantages. Such fiber-reinforced composite strength members may include a single fiber-reinforced composite strength element (e.g., a single rod), as shown in FIG. 1A. An example of such a configuration is disclosed in U.S. Patent No. 7,368,162 to Hie et al., cited above. Alternatively, the composite strength member may be constructed from a plurality of individual fiber-reinforced composite strength elements (e.g., individual rods) operatively combined (e.g., twisted or braided together) to form the strength member, as shown in FIG. 1B. Examples of such multi-element composite strength members include, but are not limited to, the multi-element aluminum matrix composite strength member shown in U.S. Pat. No. 6,245,425 to McCullough et al., the multi-element carbon fiber strength member shown in U.S. Pat. No. 6,015,953 to Tosaka et al., and the multi-element strength member shown in U.S. Pat. No. 9,685,257 to Daniel et al., each of which is incorporated herein by reference in its entirety. Other configurations for fiber-reinforced composite strength members may be used.

[0054] Referring again to the embodiment of FIG. 1A, the overhead electrical cable 120A includes a first conductive layer 122a including a plurality of conductive strands 124a helically wrapped around a fiber-reinforced composite strength member 126 including a single fiber-reinforced composite strength element 127. The conductive strands 124a can be made of a conductive metal such as copper or aluminum, and are typically made of aluminum, e.g., hardened aluminum, annealed aluminum, and / or aluminum alloys, for use in bare overhead electrical cables. Conductive materials (e.g., aluminum) do not have sufficient mechanical properties (e.g., sufficient tensile strength) to be self-supporting when stretched between support towers to form an overhead electrical transmission line for electric power transmission and / or distribution. Thus, the overhead electrical cable 120A includes a strength member 126 to support the conductive layer 124a / 124b when the overhead electrical cable 120A is stretched between support towers under high mechanical tension.

[0055] As shown in FIG. 1A, the conductive strands 124a / 124b have a substantially trapezoidal cross-section, although other configurations, such as circular cross-sections, may be employed. The use of polygonal cross-sections, such as trapezoidal cross-sections, advantageously increases the cross-sectional area of ​​the conductive metal for the same effective cable diameter, as compared to strands having, for example, circular cross-sections. As shown in FIG. 1A, the overhead electrical cable 120A typically includes a second conductive layer 122b that includes a plurality of conductive strands 124b helically wrapped around the first conductive layer 122a. It will be appreciated that such an overhead electrical cable may include a single conductive layer or three or more conductive layers, depending on the desired application of the overhead electrical cable.

[0056] Figure 1B illustrates an embodiment of an overhead electrical cable 120B similar to the electrical cable illustrated in Figure 1A, where strength member 128 includes a plurality of individual fiber-reinforced strength elements (e.g., strength element 129) that are stranded or twisted together to form strength member 128. Although shown in Figure 1B as including seven individual strength elements, it will be understood that the multi-element strength member may include any number of strength elements suitable for a particular application.

[0057] 2A and 2B show cross-sectional views of two examples of fiber-reinforced composite strength elements. FIG. 2A shows a fiber-reinforced strength element 220A having an inner core 228A that includes longitudinally extending carbon reinforcing fibers in a polymer matrix, such as a thermoplastic or thermosetting polymer. The inner core 228A is surrounded by an outer polymer layer 230A made of an insulating (e.g., high dielectric constant) polymer, such as PEEK (polyetheretherketone). The layer 230A protects the carbon fibers of the inner core 228A from contact with the conductive layer (see FIG. 1), which may cause galvanic corrosion of aluminum. In the embodiment shown in FIG. 2B, the strength element 220B includes an inner core 228B of longitudinally extending carbon fibers in a polymer matrix and an outer layer 230B of insulating glass fibers (e.g., continuous glass fibers) in a polymer matrix. The outer layer 230B of fiberglass provides robust protection for the carbon fibers from contact with the conductive layer and provides high flexibility to the strength element 220B, allowing the strength element and electrical cable to be wound on a spool for storage and transportation without damaging the strength element 220B. Typically, when a strength member is comprised of multiple strength elements, the individual strength elements will have a smaller diameter than a single element strength member. See Figures 1A and 1B above. Such strength members may include a layer (e.g., wrapping) that surrounds the bundle of strength elements. It will also be understood that not all strength members require an insulating layer.

[0058] As described above, the fiber-reinforced composites from which the strength elements are constructed include reinforcing fibers operatively arranged in a bonding matrix. The reinforcing fibers may be substantially continuous reinforcing fibers extending the entire length of the fiber-reinforced composite and / or may include short reinforcing fibers (e.g., fiber whiskers or chopped fibers) dispersed throughout the bonding matrix. The reinforcing fibers may be selected from a wide range of materials, including, but not limited to, carbon, glass, boron, metal oxides, metal carbides, high strength polymers such as aramid or fluoropolymer fibers, balsa fibers, and the like. Carbon fibers are particularly advantageous in many applications due to their very high tensile strength and / or relatively low coefficient of thermal expansion (CTE).

[0059] The bonding matrix may include a plastic (e.g., a polymer), such as, for example, a thermoplastic or a thermosetting polymer. For example, the bonding matrix may include a thermoplastic polymer, including a semi-crystalline thermoplastic. Specific examples of useful thermoplastic resins include, but are not limited to, polyetheretherketone (PEEK), polypropylene (PP), polyphenylene sulfide (PPS), polyetherimide (PEI), liquid crystal polymer (LCP), polyoxymethylene (POM or acetal), polyamide (PA or nylon), polyethylene (PE), fluoropolymers, and thermoplastic polyesters. Other examples of polymeric materials useful for the bonding matrix include addition-cured phenolic resins, such as bismaleimide (BMI), polyetheramides, various anhydrides, or imides.

[0060] The bonding matrix may also include a thermosetting polymer. Examples of useful thermosetting polymers include, but are not limited to, benzoxazines, thermosetting polyimides (PI), polyetheramide resins (PEAR), phenolic resins, epoxy-based vinyl ester resins, polycyanate resins, and cyanate ester resins. In an exemplary embodiment, vinyl ester resins are used in the bonding matrix. Another embodiment includes the use of epoxy resins such as the epoxy resin, which is the reaction product of epichlorohydrin and bisphenol A, diglycidyl ether of bisphenol A (DGEBA). Hardeners (e.g., hardeners) for epoxy resins can be selected depending on the desired properties and processing method of the fiber-reinforced composite strength member. For example, hardeners can be selected from aliphatic polyamines, polyamides, and modified versions of these compounds. Anhydrides and isocyanates can also be used as hardeners.

[0061] The bonding matrix may be a metal matrix, such as an aluminum matrix. An example of an aluminum matrix fiber reinforced composite is shown in the above-mentioned US Patent No. 6,245,425 to McCullough et al.

[0062] One particularly advantageous composite strength member configuration for overhead electrical cables is the ACCC® composite configuration available from CTC Global Corporation, Irvine, Calif., and shown in U.S. Patent No. 7,368,162 to Hiel et al., supra. In a commercial embodiment of the ACCC® electrical cable, the strength member is a single-element strength member of substantially circular cross-section that includes an inner core of substantially continuous reinforcing carbon fibers disposed in a polymer matrix. The carbon fiber core is disposed in the polymer matrix and surrounded by a rigid insulating layer of glass fibers selected to insulate the carbon fibers from the surrounding conductive aluminum strands. See FIG. 2B. Glass fibers also have a higher modulus of elasticity than carbon fibers and provide bendability, so that the strength member and electrical cable can be wound on a spool for storage and transportation.

[0063] Fiber-reinforced composite strength members useful in overhead electrical cables can be characterized in several ways. One feature can be the length of the strength member. For example, strength members for overhead electrical cables are typically manufactured in very long lengths. In a particular feature, the strength members as manufactured can have a length of at least about 1000 meters, such as at least about 3500 meters, such as at least about 5000 meters, or even at least about 7500 meters. Often, immediately after manufacturing the strength members, the strength members are typically wound onto spools (e.g., bobbins) for storage and / or transportation of the strength members, such as for transportation to a twisting facility where the strength members are twisted with conductors to form an electrical cable. The strength members of the present disclosure do not have a specific upper limit on their length, but as a practical matter, storage / transport spools will have a maximum capacity of about 9000 meters or less, such as about 8000 meters or less of strength members. It will be appreciated that the maximum capacity of a spool will depend on the diameter of the strength member (or, for example, the number of strength elements that make up the strength member) that is wound on the spool.

[0064] The length of the fiber-reinforced composite strength members may also be characterized as the electrical cable is formed, e.g., when the strength members are stranded with the conductors. As noted above, this typically occurs during the stranding process, where the strength members are pulled from a spool, stranded with the conductors (e.g., conductive strands), and the thus-formed electrical cable is wound onto another spool for storage and / or transportation of the electrical cable. Because the conductive strands add volume in addition to the volume of the strength members, the length of the electrical cable that can be stored on the spool is reduced compared to the strength members alone. Thus, for example, the length of the electrical cable and the length of the strength members in this state are typically about 4500 meters or less, e.g., about 4000 meters or less.

[0065] The length of the electrical cable and underlying fiber-reinforced composite strength members may also be characterized when the electrical cable is installed on a support tower to form an electrical line. To form an electrical line, the electrical cable is unwound from a spool and operatively attached to a support tower (e.g., a pylon) such that the electrical cable is suspended a safe distance above the ground. The electrical cable must be cut at specific intervals along the path of the electrical line and reconnected using cable hardware such as conductive splices and / or dead-end structures. The length of the electrical cable may be as short as the distance between two adjacent support towers (e.g., if the electrical line is bent) or may span several support towers before being cut and reconnected using hardware. Thus, the installed electrical cable and underlying strength members may have a length of at least about 50 meters, such as at least about 100 meters, such as at least about 250 meters or more, or at least about 500 meters or more. Some electric lines may have lengths up to about 3000 meters, for example a line strung across a river or valley in a single span, or across continuous terrain suspended by multiple towers forming multiple spans.

[0066] As noted above, a fiber reinforced composite strength member can have a range of diameters, such as the diameter of a circular cross section, the effective diameter of a non-circular cross section, or the effective diameter of a plurality of interwoven or twisted composite strength elements forming the strength member. While there is no particular lower limit on the diameter, the diameter is typically at least about 1 mm, such as at least about 2 mm or at least about 3 mm. Similarly, there is no particular upper limit on the diameter of a strength member, but the diameter is typically no more than about 30 mm, such as no more than about 20 mm, no more than about 15 mm, such as no more than about 11 mm.

[0067] Fiber-reinforced composite strength members configured for use in overhead electric cables are also characterized in terms of the minimum tensile strength required for safe installation under high mechanical tension on a support tower. In this regard, it is generally desirable for the strength members to have a tensile strength of at least about 1900 MPa, such as at least about 2000 MPa, such as at least about 2050 MPa. Since it is typically desirable to have as high a tensile strength as possible, there is no practical upper limit on the tensile strength of the strength members. As a result, the upper limit of the tensile strength is limited only by the available materials, e.g., the tensile strength of the available reinforcing fibers. Considering the tensile strength of currently available reinforcing fibers, the practical upper limit of the tensile strength is about 3500 MPa.

[0068] While tensile strength is one of the primary properties of fiber-reinforced composite strength members, other properties may be desirable for use in certain applications, such as overhead electrical cables. For example, it is also desirable for strength members in overhead electrical lines to have a low coefficient of thermal expansion (CTE) to reduce the occurrence of line sag when the electrical line overheats. For example, strength members may have a coefficient of thermal expansion (CTE) of approximately 30×10 -6 / ℃ or less, for example, about 20×10 -6 / °C or less, for example, about 10 x 10 -6 / ℃ or less, for example, about 7.5x10 -6 / ℃ or less, for example, about 5x10 -6 / °C or less, or even about 2.5x10 -6 / °C or less. In one aspect, the CTE of the strength members is about 2.0×10 -6 / °C or less. In some embodiments, the strength members have a resistance of about -0.5×10 -6 / °C.

[0069] Although the foregoing properties of the fiber-reinforced strength members have been disclosed as being desirable for use in overhead electrical cables, similar properties may also be desirable when the strength members disclosed herein are used in other structures, such as bridge cables and messenger cables.

[0070] According to the present disclosure, a fiber reinforced composite strength member includes at least one fiber reinforced composite strength element, the strength element including at least one elongated continuous optical fiber. The optical fiber may be embedded within the fiber reinforced composite (e.g., within a bonding matrix) and may extend from a first end of the strength element to a second end of the strength element. The optical fiber is configured to transmit light from the first end of the strength element to the second end of the strength element. With appropriate selection of the optical fiber(s), placement of the optical fiber(s), and preparation of the ends of the fiber reinforced composite strength element, the strength element can be probed using the systems and methods disclosed herein to assess the structural integrity of the strength element, e.g., to assess the structural integrity of a strength member including the strength element. While a single optical fiber can be utilized, the effectiveness of the systems and methods disclosed herein can be improved by including multiple optical fibers in a spaced apart relationship within the fiber reinforced composite. Thus, although the present disclosure may refer to the use of optical fibers (e.g., multiple optical fibers), the disclosure is not so limited.

[0071] The term "optical fiber" as used herein refers to an elongated, continuous fiber configured to transmit incident light over the entire length of the fiber. Typically, an optical fiber includes a transmissive core and a cladding layer surrounding the core that is made of a different material (e.g., having a different refractive index) to, for example, reduce the loss of light from the transmissive core passing through the exterior of the optical fiber. This is in contrast to, for example, structural fibers (e.g., structural glass fibers) that have a homogenous composition and are typically arranged in a composite material as a fiber tow (i.e., an untwisted bundle of individual filaments).

[0072] The optical fiber used in the strength element can be, for example, a single mode optical fiber or a multimode optical fiber. A single mode optical fiber has a small diameter transparent core (e.g., about 9 μm in diameter) surrounded by a cladding with a diameter of about 125 μm. A single mode fiber is configured to be capable of propagating only one mode of light. A multimode optical fiber has a larger transparent core (e.g., about 50 μm in diameter or more) capable of propagating multiple modes of light. It is an advantage of the present invention that the system and method for probing can use virtually any type of optical fiber, with single mode optical fibers being preferred for their relatively low cost compared to multimode optical fibers. The optical fiber can be fabricated entirely from one or more polymers. However, polymer optical fibers may not have sufficient heat resistance to withstand the fabrication and / or use of the strength element, and it is currently preferred to utilize single mode glass fibers.

[0073] The optical fiber may be linearly disposed over the entire length of the strength element. In other words, the optical fiber may be longitudinally oriented and collinear with the central longitudinal axis of the strength element. In an alternative configuration, one or more optical fibers may be non-linear, i.e., wrapped (e.g., helically twisted) with respect to the central longitudinal axis of the strength element.

[0074] One feature of the fiber reinforced composite strength element according to the present disclosure is that at least one end of the strength element has an end face configured to facilitate transmission of light (e.g., infrared light) through the strength element to an optical fiber disposed within the fiber reinforced composite without the need to separate (e.g., separate) the optical fiber from the fiber reinforced composite. Because the optical fiber is very small (e.g., only about 250 μm in diameter, including the outer coating), it is difficult to easily locate (e.g., visually locate) within the fiber reinforced composite. According to the present disclosure, for the scanning system and method to be performed, it is not necessary to separate the optical fiber (e.g., the end of the optical fiber) from the fiber reinforced composite surrounding the optical fiber. That is, the strength element can be configured such that the optical fiber is embedded in the fiber reinforced composite and does not extend beyond the end face of the fiber reinforced composite. In most applications, it is desirable for each end (e.g., first and second ends) of the strength element to be configured to allow light to be transmitted into the strength element at the first end and transmitted out of the strength element at the second end for detection.

[0075] In another aspect, the end faces of the strength elements can be described as being very smooth. For example, the end faces may be characterized as polished end faces (e.g., end faces polished to remove ridges, scratches, or other small surface features). As described below, the end faces of the strength elements can be polished with a relatively fine abrasive to remove surface features that may result from cutting the strength element with a cutting blade.

[0076] In another aspect, the end faces of the strength elements can be described as being substantially orthogonal to the central longitudinal axis of the strength element. That is, the end faces can be characterized as planes oriented at or very close to 90° to the longitudinal axis. As used herein, substantially orthogonal means that the end faces are oriented at least within ±5° of 90° to the longitudinal axis. In one aspect, the end faces are oriented within ±2° of 90° to the longitudinal axis of the strength element. For example, the end faces may be oriented within ±1° of 90° to the longitudinal axis, such as, for example, within ±0.5° of 90° to the longitudinal axis. Such orthogonal end faces can be formed, for example, by cutting the end of a fiber-reinforced composite while the composite is held (e.g., gripped) in such an orthogonal position relative to a cutting blade used to cut the end of the composite. It has been discovered that forming an end surface that has a perpendicular relationship to the longitudinal axis of the intensity element can enable the transmission of light into and out of an optical fiber without requiring that a light source be directly (e.g., physically) coupled to the optical fiber and without requiring that the optical fiber be located (e.g., visually identified) within the composite. An example of a tool that can be used to form such an end surface is described below.

[0077] The systems and methods disclosed herein for the inspection of strength elements can be used to assess the structural integrity of the strength element, for example, to determine whether the strength element (e.g., fiber-reinforced composite) contains any breaks or other similar defects, for example, from the manufacture or handling of the strength element. In order to provide a reliable assessment, and depending on the size and configuration (e.g., diameter and / or cross-section) of the strength element, it may be desirable for the strength element to include at least a second elongated and continuous optical fiber embedded within the fiber-reinforced composite. The strength element may include at least a third optical fiber or at least a fourth optical fiber, for example, to increase the probability that a break in the fiber-reinforced composite will also break (e.g., break) the optical fiber, for example, significantly reducing or blocking the optical transmission of the optical fiber, in order to provide a reliable assessment. Multiple optical fibers are particularly useful when a single strength element is used as a strength member. It is desirable for the optical fiber to meet the above characteristics, for example, that the optical fiber does not extend beyond the end face(s) of the fiber-reinforced composite.

[0078] When the fiber reinforced composite strength element includes three or more optical fibers, the optical fibers may be arranged concentrically around the central longitudinal axis of the strength element and may be arranged equidistant from the longitudinal axis and / or equidistant from each other. This can enhance the ability of the system and method to detect defects in the fiber reinforced composite by distributing the optical fibers uniformly throughout the cross section of the strength element. In one particular embodiment, the strength element includes at least four optical fibers arranged concentrically around the longitudinal axis and approximately equally spaced from each other, for example, at an angle of about 90° around the cross section of the strength element. In one feature, the central longitudinal axis of the strength element is free of optical fibers, for example, the strength element does not include a centrally located optical fiber. It is believed that placing optical fibers along the central axis does not contribute meaningfully to the effectiveness of the inspection system and method. This is because the probability of a break traveling close to the central axis of the strength element and the probability of breaking one or more optical fibers spaced around the central axis without traveling very close are very low.

[0079] In the above embodiments, in which the strength elements include a central composite core of reinforcing fibers, such as a core including carbon fibers, and an insulating layer surrounding the central core, such as a layer of glass fibers in a bonding matrix, the optical fibers may be advantageously embedded at different locations within the fiber-reinforced composite, i.e., at the interface between the central core and the insulating layer, at different distances from the central axis of the core and / or at different angles relative to the central axis. This location at the interface may increase the probability that the optical fibers will be destroyed when a break occurs in the strength elements.

[0080] 3A-3F, cross-sectional views of strength elements according to embodiments of the present disclosure are shown. The configuration of the fiber reinforced sections of the strength elements 326A-326F are similar to the strength element shown in FIG. 2B and include an inner core of high tensile fiber surrounded by an outer layer of insulating material (e.g., an inner core including carbon fiber surrounded by an outer layer including glass fiber). As shown in FIG. 3A, the strength element 326A includes four optical fibers 323a-d concentrically arranged within the strength element 426 around a central axis and spaced apart from the central axis. As shown in FIG. 3A, the fibers 323a-d are located at or very close to the boundary 329A between the inner core 328A and the outer layer 330A. The four optical fibers are also equally spaced around the central axis, e.g., radially spaced at approximately 90° intervals. As shown in FIG. 3B, the optical fibers 323e-g are located very close to the outer surface of the strength element 326B and radially spaced at approximately 120° intervals. Positioning in close proximity to the outer surface may be advantageous for early detection of damage occurring (e.g., caused) at the outer surface. However, the optical fibers 323e-g should not be positioned so close to the outer surface that they become exposed and damaged, for example, by direct contact with the outer conductive layer. FIG. 3C illustrates an embodiment of a strength element 326C, in which four optical fibers 323h-323k are embedded within the inner core 328C. FIG. 3D illustrates an embodiment of a strength element 326D, in which five optical fibers are positioned at the boundary 329D between the inner core 328D and the outer layer 330D. The five optical fibers are substantially equidistant from the central axis of the strength element and are radially spaced substantially equally apart, i.e., at intervals of about 72°. FIG. 3D illustrates that the strength element may include any number of optical fibers, including five or more optical fibers. FIG. 3E illustrates an embodiment of a strength element 326E, in which a first group of optical fibers is positioned at a first distance from the central axis of the strength element and a second group of optical fibers is positioned at a second distance from the central axis, the second distance being different from the first distance. FIG. 3F illustrates an embodiment of an intensity element 326F in which the optical fibers are positioned along and surrounded by optical fibers spaced apart from the central axis of the intensity element 326F.It will be understood that the arrangements of the optical fibers within the intensity elements shown in Figures 3A-3F are merely examples of possible arrangements, and that the present disclosure is not limited to these particular arrangements.

[0081] As mentioned above, it may be advantageous to form a smooth end face to allow the transmission of light into and out of the optical fiber, for example by polishing the end face. It has been found that many commercially available optical fibers include two or more polymer layers (i.e., an inner layer of a relatively soft polymer material to protect the glass core, and an outer layer of a harder polymer) surrounding a transparent core and cladding layer. The function of the softer polymer layer is to reduce light loss due to microbending of the optical fiber in certain applications. However, it has been found that when the end face of a strength element including the end of an optical fiber is polished, the mechanical action of the polishing process and / or the heat generated by the polishing process displaces the soft polymer layer and at least partially covers the transparent glass core of the optical fiber. Even a small amount of coverage by the displaced polymer can inhibit the transmission of light into and / or out of the optical fiber. Thus, in one feature, the optical fiber does not include a softer polymer layer. For example, the optical fiber may include a transparent glass core and cladding layer for the transmission of light and a single protective (e.g., hard) polymer layer surrounding the glass core and cladding, for example, without an intervening material layer. As a result, covering of the ends of the glass core by displaced polymer is reduced or eliminated, improving the transmission of light into and out of the optical fiber. In one aspect, the single protective polymer layer has a tensile modulus of at least about 1000 MPa, such as up to about 4500 MPa. Examples of such polymers can include acrylate-based polymers and polyimides. In another aspect, the optical fiber can be free of a polymer (e.g., protective) layer.

[0082] The strength elements described above can be manufactured by means known to those skilled in the art, including the methods described in the above-mentioned US patents. In one particular embodiment, the strength elements are formed by a pultrusion process in which continuous reinforcing fiber (e.g., carbon fiber and glass fiber) tows are pulled through a bonding matrix material (e.g., through an epoxy resin bath), which is then cured to bond the fibers to form a fiber-reinforced composite. Optical fibers are supplied in continuous lengths (e.g., thousands of meters) on spools by manufacturers in a manner similar to fiber tows (e.g., carbon fiber and glass fiber tows). Thus, optical fibers can be incorporated into the pultrusion process together with the reinforcing fibers without significant difficulty.

[0083] Accordingly, one embodiment of the present disclosure relates to a method for manufacturing an elongated fiber-reinforced composite strength element configured for use in a strength member. The method may include forming an elongated fiber-reinforced composite having a longitudinal central axis and including a bonding matrix and a plurality of reinforcing fibers disposed within the bonding matrix. At least a first optical fiber is embedded within the fiber-reinforced composite, for example, during formation of the composite, such that the optical fiber extends from a first end of the composite to a second end of the composite. For example, the optical fiber may be integrated into a pultrusion process in which a reinforcing fiber tow is impregnated with a resin that is cured from the bonding matrix. The optical fiber is typically provided on a spool (bobbin) in a similar manner as the reinforcing fiber tows, and therefore may be pulled through a pultrusion system in a similar manner. In one embodiment, the optical fiber is provided with one or more polymer layers, and the polymer layers are removed before the optical fiber is combined with the reinforcing fibers and impregnated with the resin. For example, the optical fiber is subjected to a heat treatment step to remove (e.g., volatilize) the polymer layers. In one embodiment, the heat treatment step includes directing a laser at the optical fiber just before the optical fiber is mixed with the reinforcing fibers.

[0084] As described above, the optical fiber may be oriented linearly (e.g., collinear with the central longitudinal axis of the strength element) or may be wound (e.g., helically wound) about the central longitudinal axis of the strength element.

[0085] After forming a sufficient length of the fiber-reinforced composite (e.g., by pultrusion), the composite is cut proximate to a first end of the composite to form a substantially flat first cut end surface. The cut end surface is polished to form an elongated fiber-reinforced composite strength element having a polished first end surface, the polished first end surface including the fiber-reinforced composite and a first end of an optical fiber. As a result of the above method, the polished end of the strength element including the optical fiber will have the ability to efficiently receive and transmit light, for example, through the optical fiber, without the need to physically separate the optical fiber from the surrounding fiber-reinforced composite.

[0086] As discussed above, the strength element may include one or more (e.g., four or more) optical fibers configured (e.g., embedded within a fiber-reinforced composite) to increase the probability that the optical fibers will be destroyed by a fracture or other imperfection in the surrounding composite. Thus, the method may include embedding a plurality of optical fibers, e.g., two or more optical fibers, as described above.

[0087] In the pultrusion process, after the bonding matrix has fully cured, the pultruded fiber-reinforced composite is typically collected on a spool. Since the length of the fiber tows and optical fibers significantly exceeds the length of the composite that can be stored on the spool, the elongated composite is finally cut before the storage capacity of the spool is exceeded. Typically, such cutting is performed by a simple shearing action (e.g., using bolt cutters) or a toothed (serrated) saw, resulting in rough, splintered ends of the fiber-reinforced composite. According to an embodiment, it may be desirable to probe the strength elements while they are placed on the spool. Thus, the fiber-reinforced composite may be wound on the spool such that both the first and second ends of the composite are exposed, for example, through a side opening in the spool such that one or both ends are separated from the bulk of the composite wound on the spool. Thus, in one embodiment, at least one end, and preferably both ends, of the fiber-reinforced composite are cut and ground to form strength elements (e.g., as described above) so that inspection systems and methods can be applied to the strength elements while they are disposed on the spool.

[0088] In one embodiment, a manufacturer of strength elements may wish to "stress test" the strength elements before they are shipped (e.g., before the strength elements are shipped to a stranding facility for stranding strength members formed from the strength elements with conductors to form an electrical cable). Such stress testing involves unwinding the strength elements from one spool and winding the strength elements onto another spool, where the strength elements are threaded through one or more wheels (e.g., small pulleys) between the two spools. By appropriately selecting the size and placement of the wheels, a known stress is applied to the strength elements to ensure that the strength elements do not break under the known stress (e.g., ensure that the strength elements do not have significant manufacturing defects). Thus, according to one embodiment, a system and method for scrutiny of strength elements is applied to the strength elements after stress testing to determine whether the stress elements passed the stress test (e.g., to determine whether the strength elements broke during the stress test). For example, the system and method can be applied after stress testing when the strength elements are wound onto a second spool. If the strength element is determined to pass the stress test using the inspection system and method, the spool-wound strength element may be shipped for twisting.

[0089] In any case, in one embodiment, the cutting step may be performed in a manner that is likely to form an orthogonal end surface, as described above. For example, the cutting step may include cutting the fiber-reinforced composite with a mechanically actuated (e.g., motorized) cutting blade. Abrasive cutting blades, which cut the material primarily due to the presence of abrasive grains (i.e., high hardness particulate material) on the cutting blade, are generally preferred over cutting blades that include cutting teeth. Although the use of fine cutting teeth to cut the fiber-reinforced composite is not precluded, it is believed that cutting teeth leave a rougher surface than abrasive grains, making the polishing step after the cutting step more difficult (e.g., more time consuming). In one feature, the abrasive cutting blade includes abrasive grains having an ultra-fine or coarser size, e.g., at least about 30 μm (about 600 grit), e.g., at least about 40 μm (about 360 grit) or at least about 68 μm (about 220 grit). It will be appreciated that the selection of cutting grit can be made taking into consideration the speed of the cutting edge (e.g., rotational speed) and the desire for rapid cutting and sharpening, i.e., coarser grits can cut faster but will require longer subsequent sharpening times.

[0090] As described in certain features above, to form a substantially orthogonal end surface, the cutting step can include fixing (e.g., mechanically fixing) a first end of the fiber-reinforced composite such that the first end is disposed substantially orthogonal relative to the cutting edge (e.g., relative to the cutting blade) during the cutting step. For example, the fiber-reinforced composite can be mechanically clamped such that the composite is disposed orthogonal to the cutting edge and cannot move off-axis in any meaningful way during the cutting step.

[0091] After cutting, the end surface is polished to provide a smooth end surface. For example, the polishing step can include polishing the cut end surface with a polishing surface. For example, the polishing surface can include polishing grains having an ultrafine size, for example, a grain size of about 25 μm (800 grit) or less, or even about 22 μm (1000 grit) or less. As characterized in another way, the polishing step can be performed with a polishing grain smaller than the abrasive grains used in the cutting step.

[0092] As noted above, some optical fibers are provided by the manufacturer with a soft polymer layer to reduce microbending losses, and such soft polymer may coat the end of the optical fiber's permeable core during the cleaving and / or polishing steps. If the optical fiber includes such a layer, one technique for reducing or removing such coating is to temporarily harden the soft polymer layer to reduce its tendency to displace and coat the optical fiber's permeable core. For example, the end face may be cooled before and / or during the cleaving and polishing steps to harden the polymer layer. In one feature, the end face is cooled by applying a cooling liquid or gas to the end face. Examples include applying a compressed gas (e.g., compressed nitrogen gas, carbon dioxide gas, hydrocarbon gas, Freon, etc.) to the end face before and / or during the cleaving and polishing steps.

[0093] Methods for forming the end faces of the strength elements are described above as including mechanically cutting and grinding the ends of the fiber-reinforced composites, for example, using cutting blades and abrasive surfaces. However, it is contemplated that strength elements having desired end faces may be formed by other means. For example, a water jet or laser may be used to obtain an end face having desirable characteristics for effective light transmission in the probing systems and methods disclosed herein.

[0094] The above describes the manufacture of strength elements having end face(s) configured (e.g., cleaved and polished) to allow for the transmission of light in and out of optical fibers embedded in the strength elements. This allows the manufacturer of the strength elements to vet the strength elements before they are shipped to an end user or to an intermediary, such as a facility that strands the strength elements with conductors to form an electrical cable. The systems and methods can also be implemented at other times in addition to or instead of the manufacturer. Such implementations may also require the end user and / or intermediary to prepare the ends of the strength elements according to the preceding description. For example, as described above, when a strength member (e.g., including one or more strength elements) is to be stranded with conductors to form an electrical cable, the strength member is pulled from a spool and stranded with conductive strands. The conductive strands add volume in addition to the volume of the strength member, so the length of electrical cable that can be stored in a spool is reduced compared to the spool capacity of the strength member alone. Thus, the strength members need to be cut at some point, such as when a spool of electrical cable reaches its capacity. As a result, Stranda may desire to prepare the ends of the strength members in accordance with the methods described above so that Stranda or a Stranda customer can inspect the electrical cable after it is wound onto a spool.

[0095] Similarly, as explained above, when the strength members are being installed (e.g., when an overhead electrical cable including the strength members is being strung on support towers), multiple cuts may be required along the length of the electrical cable to accommodate the distances between the support towers, particularly to account for turns (e.g., angles) in the routing of the electrical line. Thus, in some embodiments, the strength element(s) may be cut and ground according to the methods described above during installation of the electrical cable on the support towers.

[0096] In one embodiment of the present disclosure, a tool is disclosed that is particularly useful for cutting and grinding strength elements. The tool is configured to cut and grind the ends of a fiber-reinforced composite in one step, thereby reducing the amount of effort and the possibility of error in cutting and grinding to form a strength element for inspection. The tool includes a planar body having a cutting blade along at least one edge of the planar body and an abrasive surface covering at least a portion of the planar body. An alignment member is operatively associated with the planar body and configured to operatively align an elongated fiber-reinforced composite having a longitudinal axis to the planar body such that the cutting blade of the planar body is configured to move and cut the composite substantially perpendicular to the longitudinal axis to form a cut surface, and the abrasive surface is configured to abrade the cut surface as the cutting blade moves through the composite.

[0097] The planar body that performs the cutting and polishing can take a variety of forms (e.g., a continuously moving polygonal surface as found in a belt polisher). In one aspect, the planar body is substantially circular and is rotated (e.g., by an electric motor) to cut the fiber-reinforced composite. In this regard, a motor may be operatively connected to the planar body, where the motor is configured to rapidly rotate the planar body about a central axis of the planar body. Although the cutting blade can include multiple cutting teeth, it is advantageous to form the cutting blade with an abrasive surface, as described above, to minimize the formation of rough and / or splintered ends of the composite. In one aspect, the abrasive cutting blade includes abrasive grains having an ultra-fine or coarser size, e.g., at least about 30 μm (about 600 grits), e.g., at least about 40 μm (about 360 grits) or at least about 68 μm (about 220 grits). It will be appreciated that the selection of abrasive cutting grains can be made taking into consideration the speed of the cutting edge (e.g., rotational speed) and the desire for rapid cutting and polishing, i.e., coarser abrasive grains can cut faster but will require longer polishing times.

[0098] The planar body includes an abrasive surface that covers the entire surface of the planar body or only a portion thereof. The abrasive surface may include abrasive grains having an ultrafine size, for example, a grain size of about 25 μm (800 grits) or less, or even about 22 μm (1000 grits) or less. As characterized in another way, the abrasive surface may include abrasive grains that are finer than the abrasive grains used on the cutting blade. In one feature, the abrasive surface includes at least two different abrasive grain sizes, where coarser grains are applied near the outer portion of the abrasive surface and finer grains are applied near the center portion of the abrasive surface. In this way, the cutting surface can first contact the coarser abrasive grains to quickly remove larger surface features, and then contact the finer abrasive grains to remove smaller surface features.

[0099] The abrasive surface may be located slightly higher than the underlying surface of the planar body to allow the application of a small amount of pressure by the abrasive surface onto the end surface of the fiber-reinforced composite. For example, the abrasive surface may be located at least about 0.1 mm (e.g., at least about 0.3 mm) and no more than about 1.2 mm (e.g., no more than about 1.0 mm) higher than the surface of the planar body. For example, the abrasive surface may include abrasive grains disposed on a thin substrate (e.g., a paper substrate) that is attached (e.g., glued) to a particularly smooth flat surface. Alternatively, or in addition to a raised abrasive surface, the tool may include a mechanism (e.g., a spring) configured to press the abrasive surface toward the end of the fiber-reinforced composite to be abraded.

[0100] The tool may conveniently be a handheld tool, e.g., a tool that can be carried and operated by an operator in a variety of environments. For example, when installing an overhead electric cable, it is necessary for the operator to cut the electric cable while high above the ground, often in a bucket that is vertically movable. Providing a tool that can be easily carried and operated by an operator in such a small space provides a great advantage. In this regard, the tool may include a battery for powering the movement mechanism of the planar body (e.g., the movement mechanism of the cutting blade and the grinding surface). The battery may be, for example, a rechargeable battery. For example, to improve the portability and ease of use of the tool, a battery having a capacity in the range of about 2 ampere hours to about 12 ampere hours may be utilized. In another feature, the battery may have a voltage of about 12 volts to about 20 volts. A battery having these characteristics may provide sufficient power for the tool to reliably operate for a reasonable period of time while maintaining the tool in a form that is easily carried and operated by an operator.

[0101] The tool may also include a gripping portion (eg, a handle) to allow an operator to grip and freely manipulate the tool, similar to, for example, a hand-held drill. Certain fiber-reinforced composites may include materials (e.g., carbon fiber) that may pose a hazard to an operator when the cutting blades and abrasive surfaces remove material from the surface in the form of dust. In one feature, the tool includes a mechanism configured to capture dust generated during cutting and abrading. For example, the mechanism may be coupled to the planar body such that a partial vacuum is created to capture dust when the planar body moves (e.g., when the planar body rotates).

[0102] It will be understood that the cutting and polishing tools described herein may have a wide variety of applications and are not limited to cutting and polishing fiber-reinforced composites to form strength elements as described above.

[0103] The above-described strength elements having one or more optical fibers disposed therein can be used in many different applications, particularly as tensile strength members in various structures. In one embodiment of the present disclosure, the strength elements are used in strength members for overhead electrical cables.

[0104] In one embodiment, a method of inspecting a fiber-reinforced composite strength member (e.g., a member configured for use with an overhead electrical cable) is disclosed. The strength member includes strength elements formed from a fiber-reinforced composite, the composite including a bonding matrix and a plurality of reinforcing fibers operatively disposed within the bonding matrix. As described above, at least a first optical fiber is embedded in the composite and extends the entire length of the fiber-reinforced composite. The inspection method includes operably attaching an optical transmission device to a first end of the strength member, operably attaching an optical detection device to a second end of the strength member, transmitting light from the optical transmission device through the first optical fiber toward the optical detection device, and detecting the transmitted light by the optical detection device. In one feature, if no transmitted light from one or more optical fibers is detected, further evaluation of the structural integrity of the strength member can be performed, as the absence of transmitted light from one or more optical fibers may indicate that the structural integrity of the strength member is compromised.

[0105] The transmitted light may include light across a broad spectrum. For example, visible light (e.g., having a wavelength of about 400 nm to about 700 nm) may be suitable for shorter lengths of composite intensity elements or when the luminous intensity of the light source is very high. However, visible light may be too attenuated for most applications, especially over long distances.

[0106] Advantageously, the wavelength of the transmitted light may be primarily in the infrared region. For example, the wavelength (e.g., peak wavelength) of the transmitted light may be at least about 700 nm, such as at least about 800 nm. Furthermore, the wavelength of the transmitted light may be about 1200 nm or less, such as about 1000 nm or less. It is believed that light having a wavelength greater than about 1200 nm is difficult to detect at the second end of the intensity element using a conventional light sensor, such as a CCD or CMOS light sensor. It is particularly advantageous that the light source may be an incoherent light source, as compared to a coherent (e.g., single-phase) light source, such as a laser. The use of lasers is difficult because the diameter of the coherent light is small, requiring strong coupling into individual optical fibers. In contrast, the methods disclosed herein may advantageously use incoherent light sources, such as light-emitting diodes (LEDs), halogen lamps, and the like.

[0107] In one feature, the light source is an LED, and the step of transmitting the light includes energizing the LED, for example, using a battery or other power source. LEDs are reasonably inexpensive and mechanically robust. Because the intensity element may include several optical fibers located at different positions across the cross section of the intensity element, it is desirable to transmit the light toward substantially the entire cross section of the intensity element so that sufficient light is transmitted to all optical fibers for detection at the opposite end of the intensity element. In one feature, this is accomplished by moving the light source (e.g., an LED) while the light is being transmitted. For example, the light source may be rotated (e.g., mechanically rotated using a motor) or actuated (e.g., moved back and forth or oscillated) when the light is being transmitted. In one particular feature, the light source is rotated at a speed of at least about 5 revolutions per minute (rpm), such as at least about 10 rpm, when the light is being transmitted toward the end of the intensity element.

[0108] In one embodiment, the strength element can have substantially the characteristics as described above and can be manufactured as described above. For example, the end face of the strength element can include a fiber-reinforced composite and an optical fiber(s), where the optical fiber(s) does not extend beyond the end face. The end face can be polished.

[0109] Alternatively or in addition, an index-matching material (e.g., a fluid such as a gel) can be placed on the end face (e.g., the end of the optical fiber) to enhance light transmission to and / or from the optical fiber. The index-matching material is a fluid material that has a refractive index at a wavelength of interest that is the same as or very similar to that of another material, e.g., the transparent core of the optical fiber, such that a decrease in wavelength results in a higher refractive index. In one embodiment, the method includes placing a small amount of index-matching gel on the end face of the intensity element prior to light transmission, where the index-matching gel has a refractive index that is substantially the same as that of the optical fiber core. In one embodiment, the index-matching material has a refractive index that is at least about 1.40, such as at least about 1.42, or even at least about 1.44. The refractive index of the index-matching material may be about 1.50 or less, e.g., about 1.48 or less. It has been found that even a small amount of index-matching gel placed on the end face can significantly improve the transmission of light into the optical fiber.

[0110] The inspection method may be performed after manufacture of the strength elements (e.g. when the strength elements are placed on a spool), or after stress testing (e.g. bend testing) as described above, or after manufacture of the final product (e.g. after stranding the strength element(s) with the conductors), or after installation (e.g. after installation of an overhead electrical cable) to ensure the structural integrity of the electrical cable.

[0111] In another embodiment, a system for inspection of strength elements is disclosed. Without being limited thereto, the system may be used to implement the aforementioned method for inspection of strength elements. For example, the system may be configured to detect defects in a fiber-reinforced strength member (e.g., a strength member that is a component of an overhead electrical cable). In this embodiment, the system includes an overhead electrical cable, the overhead electrical cable including a fiber-reinforced composite strength member. The strength member includes a bonding matrix, a plurality of reinforcing fibers operatively disposed within the bonding matrix to form a fiber-reinforced composite section, and at least a first optical fiber disposed completely within the fiber-reinforced composite section throughout the length of the strength member. Electrical conductors are disposed around and supported by the strength member to form the electrical cable. An optical transmission device is operably connected to a first end of the strength member, the optical transmission device including a light source configured to transmit light to the first end of the optical fiber. For example, the light may have a wavelength of at least about 300 nm and no greater than about 1700 nm. The light detection device includes a light sensor operably connected to the second end of the strength member and configured to detect light from the light transmission device that has passed through the second end of the optical fiber.

[0112] As discussed above, the light source may be configured to emit light having a wavelength in the infrared range, for example, light having a wavelength of at least about 700 nm (such as at least about 800 nm). Additionally, the light source may be configured to emit light having a wavelength of about 1200 nm or less, such as about 1000 nm or less. The light source may be any useful incoherent light source, including, but not limited to, a halogen lamp or an LED. Advantageously, the light source may include a plurality of LEDs (e.g., an LED panel) assembled to increase the area (e.g., cross-sectional area) through which the light is transmitted. The light source may also be operably attached to a mechanism, such as a motor, configured to move (e.g., rotate or vibrate) the light source as it transmits light. In this manner, a substantially uniform column or beam of light is transmitted toward the end face of the intensity element, substantially increasing the likelihood that each optical fiber in the intensity element receives a sufficient amount of light to be detected at the second end of the intensity element.

[0113] The light source may be powered by any conventional means. In one embodiment, the light source is powered by a battery, e.g., a rechargeable battery. For example, to improve the portability and ease of use of the light source, a battery having a capacity ranging from about 2 amp hours to about 12 amp hours may be utilized. In another aspect, the battery may have a voltage of about 12 volts to about 20 volts. A battery having these characteristics may provide enough power to reliably operate the light source for a reasonable period of time while maintaining the light source in a form that is easily carried and operated by an operator.

[0114] The light source may also be spaced apart from the end of the intensity element during use. Despite the space, the structure of the end of the intensity element allows light from the light source to pass through the optical fiber(s), as described above. In one feature, the light source (e.g., the front surface of the light source) is spaced apart from the end face of the intensity element by at least about 0.1 mm, e.g., at least about 1.0 mm, during use. In another feature, the light source is spaced apart from the end face by no more than about 150 mm, e.g., no more than about 100 mm, e.g., no more than about 30 mm.

[0115] The strength member may include one or more strength elements as described above, including strength elements having multiple optical fibers disposed within a composite, such as at least about 2, at least about 3, or at least about 4 optical fibers. The strength members may have a range of lengths as described above and may be implemented at different times during manufacture and installation of the strength member.

[0116] The light detection device may include a light sensor for detecting the transmitted light. While it may be possible for a user to directly inspect the light (such as with the naked eye), a light detection device including a light sensor may allow for detection of relatively weak light and recording of images and / or data for remote analysis and / or archival purposes. For example, the light sensor may be a charge-coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) device. The light detection device may include, for example, a concave lens disposed between the end of the composite strength member and the light sensor and configured to focus the transmitted light onto the light sensor. The light sensor may also be connected to a computing device for analyzing and / or displaying images created by the sensor. The connection may be a wired connection or may be a wireless connection, for example, enabled through the use of an antenna.

[0117] Non-limiting examples of optical transmission and detection devices that can be used in the above-described systems or similar systems are described below. In one embodiment, a device is disclosed for transmitting light to an end of an optical fiber embedded in an elongated structural member (e.g., a strength element as described herein). The device includes a substantially rigid structure and a bore disposed at least partially through the structure, the bore having an opening at a first end of the bore. The opening and the bore are configured (e.g., shaped and sized) to receive an end of an elongated structural member having at least a first optical fiber embedded throughout the length of the structural member. The device includes a light source disposed at least partially within the structural body and proximate a second end of the bore, the light source configured to transmit light into the bore and toward the end of the elongated member when the elongated member is disposed within the first end of the bore. A power source (e.g., a battery) is operably attached to the light source.

[0118] In one feature, the light source is an incoherent light source, as opposed to a coherent light source (e.g., a single-phase light source), such as, for example, a laser. The light source may be, for example, a halogen lamp or an LED, and in one feature, the light source includes an LED. The LED may be configured to emit light within a wavelength range of at least about 300 nm and not more than about 1200 nm (e.g., a wavelength range of at least about 700 nm and not more than about 1000 nm). Wavelengths above about 1200 nm are believed to be difficult to detect using conventional light detection means. In one particular feature, the LED is configured to emit light primarily in the infrared region, such as a dominant wavelength of at least about 800 nm and not more than about 900 nm.

[0119] In another feature, the device includes a motor operably connected to the light source, the motor configured to move the light source as it transmits light into the bore, such as by vibrating the light source or rotating the light source about its central axis.

[0120] In another feature, the device includes a stop element configured to maintain a distance between the light source and the end of the structural member when the structural member is disposed within the first end of the bore. Such a configuration prevents an operator from directly contacting the end of the intensity element with the light source, reducing the possibility of damage to the light source. The stop element may be configured to maintain a distance between the end of the structural member and the light source of at least about 0.1 mm (e.g., at least about 1.0 mm) and no more than about 150 mm (e.g., no more than about 100 mm or no more than about 30 mm). For example, the stop element includes a shoulder (e.g., a step) disposed within the bore, the shoulder configured to prevent movement of the structural member past the shoulder when the member is inserted into the bore. The stop element may also include a transparent (e.g., glass) plate disposed between the end of the intensity element and the light source, and the intensity element may be pressed up against the glass plate. In this regard, a transparent gel may be applied between the glass plate and the intensity element, if desired, to facilitate transmission of light to the optical fiber(s) passed through the plate. The stop element may also be integrated into the light source, in which case, for example, the light emitting surface is arranged behind a transparent plate.

[0121] The bore may have a single size (eg, fixed diameter) or an adjustable diameter bore may be provided, for example, by providing an insert sleeve that accommodates strength elements of various diameters.

[0122] To provide durability while remaining relatively lightweight, the device body may be fabricated from a metal, such as a lightweight metal, hi one aspect, the body is fabricated from aluminum. In another embodiment, a device configured to detect light emanating from an end of an optical fiber embedded in an elongated structural member is disclosed. The device includes a substantially rigid structure and a bore disposed at least partially through the structure. The bore has an opening at a first end of the bore, the opening and the bore configured (e.g., shaped and sized) to receive an end of an elongated structural member having at least a first optical fiber embedded throughout the length of the structural member. An optical sensor is disposed within the structure proximate a second end of the bore, the optical sensor configured to receive and detect light from the optical fiber when the elongated member is disposed within the first end of the bore. A power source may be operably attached to the optical sensor.

[0123] In one feature, the light sensor is selected from a CCD sensor and a CMOS sensor. In another feature, a light blocking element is disposed at a first end of the bore. The light blocking element is configured to prevent stray light (e.g., external light) from entering the bore and interfering with the light sensor's ability to detect light from the optical fiber. For example, the light blocking element may be a material, such as an elastomeric material, configured to seal around the structural member when the structural member is disposed within the bore.

[0124] Similar to the optical transmission device, the optical detection device may include a stop element for maintaining a distance between the optical sensor and an end of the structural member when the structural member is disposed within the first end of the bore. The stop element may include, for example, a shoulder (e.g., a step) disposed within the bore, the shoulder configured to prevent movement of the structural member past the shoulder. The stop element may be configured to maintain a distance between the end of the structural member and the optical sensor of at least about 5 mm (e.g., at least about 10 mm) and no more than about 300 mm (e.g., no more than about 200 mm or no more than about 100 mm).

[0125] In one feature, the device also includes a lens, such as a concave lens, configured to focus light emanating from the optical fiber onto the light sensor. In this regard, the aforementioned stop element that maintains the distance between the light sensor and the end of the structural member can maintain an appropriate distance between the end of the structural member and the lens to enhance the efficiency of the lens.

[0126] Like the light transmitting device, the body of the light detecting device may be fabricated from metal, including lightweight metals such as aluminum. The following figures depict separate embodiments according to the present disclosure and are intended only to illustrate such embodiments and are not otherwise intended to limit the scope of the present disclosure.

[0127] 3A-3F, cross-sectional views of strength elements according to embodiments of the present disclosure are shown. The configuration of the fiber reinforced sections of the strength elements 326A-326F are similar to the strength element shown in FIG. 2B and include an inner core of high tensile fiber surrounded by an outer layer of insulating material (e.g., an inner core including carbon fiber surrounded by an outer layer including glass fiber). As shown in FIG. 3A, the strength element 326A includes four optical fibers 323a-d concentrically arranged within the strength element 426 around a central axis and spaced apart from the central axis. As shown in FIG. 3A, the fibers 323a-d are located at or very close to the boundary 329A between the inner core 328A and the outer layer 330A. The four optical fibers are also equally spaced around the central axis, e.g., radially spaced at approximately 90° intervals. As shown in FIG. 3B, the optical fibers 323e-g are located very close to the outer surface of the strength element 326B and radially spaced at approximately 120° intervals. Positioning in close proximity to the outer surface may be advantageous for early detection of damage occurring (e.g., caused) at the outer surface. However, the optical fibers 323e-g should not be positioned so close to the outer surface that they become exposed and damaged, for example, by direct contact with the outer conductive layer. FIG. 3C illustrates an embodiment of a strength element 326C, in which four optical fibers 323h-323k are embedded within the inner core 328C. FIG. 3D illustrates an embodiment of a strength element 326D, in which five optical fibers are positioned at the boundary 329D between the inner core 328D and the outer layer 330D. The five optical fibers are substantially equidistant from the central axis of the strength element and are radially spaced substantially equally apart, i.e., at intervals of about 72°. FIG. 3D illustrates that the strength element may include any number of optical fibers, including five or more optical fibers. FIG. 3E illustrates an embodiment of a strength element 326E, in which a first group of optical fibers is positioned at a first distance from the central axis of the strength element and a second group of optical fibers is positioned at a second distance from the central axis, the second distance being different from the first distance. FIG. 3F illustrates an embodiment of an intensity element 326F in which the optical fibers are positioned along and surrounded by optical fibers spaced apart from the central axis of the intensity element 326F.It will be understood that the arrangements of the optical fibers within the intensity elements shown in Figures 3A-3F are merely examples of possible arrangements, and that the present disclosure is not limited to these particular arrangements.

[0128] One embodiment of a probing system according to the present disclosure is shown generally in Figure 4. Generally characterized, the system 440 includes an optical transmission device 450, an optical sensing device 460, and an intensity element 426, for example as described above.

[0129] As shown in Figure 4, the intensity element 426 includes four longitudinally extending optical fibers, of which two optical fibers 432a / 432b are visible in Figure 4. The optical fibers are single mode optical fibers and are disposed within the intensity element 426 (e.g., offset from the central axis 434 as shown in Figure 3A).

[0130] Referring to FIG. 5, the optical transmission device 550 is shown in more detail. The device 550 includes an optical transmitter 552 for transmitting the probing light. The transmitter 552 includes a light source 566 operably coupled to a power source 568. The light source 566 is a light emitting diode (LED) having a dominant wavelength of about 850 nm. The power source 568 is a battery for mobility and convenience of use in the field, such as during or immediately after the installation of an overhead electrical cable. The LED light source 566 is configured to rotate (e.g., via a motor (not shown)) such that a sufficient amount of light from the light source 566 is incident on each of the optical fiber(s). The components of the optical transmission device 550 are enclosed (e.g., sealed) in a body 558 fabricated from a metal, such as aluminum, or a plastic, to protect the components from damage during use in the field. The body 558 includes a bore 560 having an opening at a first end configured to receive a strength element in the bore 560. The shoulder 564 is sized to prevent the intensity element from penetrating the bore to a point where the intensity element contacts the light source 566 (see FIG. 4). In other words, the shoulder 564 maintains a predetermined distance between the end of the intensity element and the light source 566.

[0131] Referring again to FIG. 4, the system also includes a light detection device 460 disposed at the end of the overhead electrical cable 420 opposite the light transmission device 450. The light detection device is shown in more detail in FIG. 6. The device 660 includes a light sensor 664 for detecting light from the light transmission device. As with the light transmission device, the components of the light detection device 660 are enclosed (e.g., sealed) within a body 658 fabricated from a metal, such as aluminum, or plastic, to protect the components from damage during use in the field. The body 658 includes a bore 670 having an opening at a first end configured to receive a strength element within the bore 670. Disposed over the opening to the bore 670 is a light shield 676 fabricated from an elastomeric material having an opening therethrough. When the strength element is inserted into the bore 670, the light shield 676 moves inward to form a light seal around the strength element to reduce the amount of stray light entering the bore 670 from the outside environment.

[0132] The shoulder 674 is sized to prevent the intensity element from penetrating the bore 670 to a point where it contacts the light sensor 664 (see FIG. 4) so ​​as to maintain a predetermined distance between the end of the intensity element and the light sensor 664. The light sensor is, for example, a CCD / CMOS sensor such as found in a digital camera. As shown in FIG. 6, the light detection device 660 includes a concave lens 662 that directs light received from a light source to the light sensor 664. However, such a concave lens may not be necessary for proper light detection.

[0133] 7A and 7B illustrate a tool 700 for cutting and grinding a strength element or similar workpiece according to an embodiment of the present disclosure. The tool 700 includes a flat, rotatable blade 704 including a cutting edge 708 and an abrasive surface 706. The abrasive surface 706 is located slightly (e.g., about 1 mm) higher than a surface 714 of the blade 704. An alignment member 710 is attached to the tool body 702 and configured to move (e.g., pivot about an axis 716) the strength element 720 relative to the cutting blade 704. The alignment member 710 aligns the strength element 720 with the cutting blade 704 such that the cutting edge 708 can cut the strength element 720 substantially perpendicular to the longitudinal axis of the strength element 720. As the cutting edge moves through the strength element, the abrasive surface 706 grinds the freshly cut surface of the strength element 720. The tool 700 is configured to be grasped by a user who can activate the cutting blade 704 using an activation button 712. A rechargeable battery 718 provides power to the tool.

[0134] While various embodiments of systems, methods and tools for inspection of intensity elements have been described in detail, modifications and adaptations of those embodiments will occur as will be apparent to those skilled in the art, but it is expressly understood that such modifications and adaptations are within the spirit and scope of the present disclosure. The technical ideas that can be understood from the above-described embodiment will be described below as supplementary notes. [Appendix 1] A system configured to detect defects in a fiber-reinforced composite strength member, comprising: A fiber reinforced composite strength member, the strength member including at least a first strength element, the first strength element comprising: A coupling matrix; a plurality of reinforcing fibers operatively disposed within the bonding matrix to form a fiber-reinforced composite; the fiber-reinforced composite strength member including at least a first optical fiber embedded within the fiber-reinforced composite and extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite; an optical transmission device operably connected to a first end of the strength member, the optical transmission device including a light source configured to transmit light having a wavelength of at least about 300 nm and no greater than about 1700 nm through the first end of the first optical fiber; an optical detection device operably connected to the second end of the strength member, the optical detection device comprising an optical detector configured to detect light from the optical transmission device that has passed through the second end of the first optical fiber. [Appendix 2] The system of Appendix 1, wherein the light source is configured to emit light having a dominant wavelength in the infrared region. [Appendix 3] The system of appendix 1 or 2, wherein the light source is configured to emit light having a dominant wavelength of at least about 800 nm. [Appendix 4] The system of any one of appendixes 1 to 3, wherein the light source is configured to emit light having a dominant wavelength of about 1000 nm or less. [Appendix 5] The system of any one of appendices 1 to 4, wherein the strength element includes at least a second optical fiber embedded in the fiber-reinforced composite and extending along the entire length of the fiber-reinforced composite. [Appendix 6] The system of Appendix 5, wherein the strength element includes at least a third optical fiber embedded in the fiber-reinforced composite and extending along the entire length of the fiber-reinforced composite. [Appendix 7] The system of Appendix 6, wherein the strength element includes at least a fourth optical fiber embedded in the fiber-reinforced composite and extending along the entire length of the fiber-reinforced composite. [Appendix 8] The system of any one of appendices 1 to 7, wherein conductors are disposed around and supported by the strength members to form an electrical cable. [Appendix 9] The system of any one of Appendices 1 to 8, wherein the electrical cable has a length of at least about 100 meters. [Appendix 10] The system of any one of Appendices 1 to 9, wherein the electrical cable has a length of about 3,500 meters or less. [Supplementary Note 11] The system described in any one of Supplementary Notes 1 to 10, wherein the first optical fiber is a single-mode optical fiber. [Appendix 12] The system of any one of Appendices 1 to 11, wherein the light source includes a light emitting diode (LED). [Supplementary Note 13] The system described in any one of Supplementary Notes 1 to 12, wherein the optical detection device includes a concave lens disposed between an end of the composite strength member and an optical sensor and configured to focus transmitted light onto the optical sensor. [Appendix 14] The system of any one of Appendices 1 to 12, wherein the optical sensor is selected from a CCD sensor and a CMOS sensor. [Appendix 15] A method of inspecting a fiber-reinforced composite strength member, the strength member including at least a first strength element, the strength element including a bonding matrix, a plurality of reinforcing fibers operatively arranged within the bonding matrix to form a fiber-reinforced composite, and at least a first optical fiber embedded in the fiber-reinforced composite and extending the entire length of the fiber-reinforced composite; operably attaching an optical transmission device to a first end of the strength member; operably attaching a light-detecting device to a second end of the strength member; transmitting light from the optical transmission device through a first optical fiber toward the optical detection device; the transmitted light being incoherent; detecting the presence of incoherent transmitted light with the light detection device. [Appendix 16] The method of appendix 15, wherein the transmitted light has a wavelength in the infrared region. [Appendix 17] The method of appendix 15 or 16, wherein the transmitted light has a dominant wavelength of at least about 800 nm. [Additional Note 18] The method of any one of Additional Notes 15 to 17, wherein the transmitted light has a dominant wavelength of about 1000 nm or less. [Appendix 19] The method of any one of Appendices 15 to 18, wherein the first strength element includes at least a second optical fiber embedded in the fiber-reinforced composite and extending along the entire length of the fiber-reinforced composite, and the step of transmitting light includes transmitting light through the second optical fiber. [Supplementary Note 20] The method of Supplementary Note 19, wherein the strength element includes at least a third optical fiber embedded in the fiber-reinforced composite and extending along the entire length of the fiber-reinforced composite, and the step of transmitting light includes transmitting light through the third optical fiber. [Supplementary Note 21] The method of Supplementary Note 20, wherein the strength element includes at least a fourth optical fiber embedded in the fiber-reinforced composite and extending along the entire length of the fiber-reinforced composite, and the step of transmitting light includes transmitting light through the fourth optical fiber. [Appendix 22] The method of any one of Appendices 15 to 20, wherein the composite strength member has a length of at least about 500 meters. [Appendix 23] The method of any one of Appendices 15 to 22, wherein the composite strength member has a length of at least about 3,500 meters. [Appendix 24] The method of any one of Appendices 15 to 23, wherein the composite strength member has a length of about 7,500 meters or less. [Appendix 25] The method of any one of Appendices 15 to 22, wherein the composite strength member is wound on a spool during the steps of transmitting light and detecting light. [Additional Note 26] The method of any one of Additions 15 to 25, further comprising the step of stress testing the composite strength element prior to the steps of transmitting light and detecting light. [Appendix 27] The method of any one of Appendices 15 to 25, wherein the conductors are stranded around the composite strength members to form an overhead electrical cable. [Supplementary Note 28] The method of Supplementary Note 27, wherein the steps of transmitting light and detecting light are performed after stranding the conductors in the composite strength members and before installing the overhead electrical cable on a support tower. [Supplementary Note 29] The method described in Supplementary Note 27, wherein the steps of transmitting light and detecting light are performed after installing the overhead electrical cable on a support tower. [Addendum 30] The method of any one of Addendums 15 to 29, wherein the optical fiber is a single-mode optical fiber. [Addendum 31] The method of any one of Addendums 15 to 30, wherein the step of transmitting light includes energizing a light emitting diode (LED). [Addendum 32] The method of Addendum 31, wherein the step of transmitting light includes mechanically rotating the LED while transmitting light. [Additional Note 33] The method of Additional Note 32, wherein the LED is rotated at a speed of at least about 5 rpm. [Appendix 34] The method of any one of Appendices 15 to 33, comprising applying an index matching gel to the first end of the strength member to facilitate transmission of light to the optical fiber. [Appendix 35] A method for preparing a fiber-reinforced composite strength element for inspection using a light source, comprising: severing the elongated fiber-reinforced composite in proximity to a first end of the elongated fiber-reinforced composite; The fiber-reinforced composite includes a bonding matrix and a plurality of reinforcing fibers disposed within the bonding matrix; at least a first optical fiber is disposed within the fiber-reinforced composite, the first optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite; the cutting forms a substantially flat first cut end surface; and polishing the first cut end surface to form a polished first end surface comprising the fiber-reinforced composite and a first end of an optical fiber, forming a fiber-reinforced composite strength element configured to be probed by an incoherent light source. [Appendix 36] A step of cutting the fiber-reinforced composite adjacent a second end of the fiber-reinforced composite, the cutting forming a substantially flat second cut end surface; and polishing the second cleaved end face to form a polished second end face comprising the fiber-reinforced composite and a second end of the first optical fiber. [Appendix 37] The method of any one of Appendices 35 to 36, wherein the fiber-reinforced composite strength element has a length of at least about 100 meters. [Appendix 38] The method of any one of Appendices 35 to 37, wherein the fiber-reinforced composite strength element has a length of about 7,500 meters or less. [Appendix 39] The method of any one of Appendices 35 to 38, wherein the step of cutting the fiber-reinforced composite includes cutting with an electrically powered abrasive cutting blade. [Appendix 40] The method of Appendices 39, wherein the abrasive cutting blade comprises abrasive grains having an abrasive grain size of at least about 30 μm. [Appendix 41] The method of any one of Appendices 39 and 40, wherein the powered abrasive cutting blade is rotated by a motor during the cutting step. [Appendix 42] The method of any one of Appendices 39 to 41, further comprising the step of fixing a first end of the fiber-reinforced composite during at least the cutting step such that the first end is positioned substantially perpendicular to a cutting blade during the cutting step. [Appendix 43] The method of any one of Appendices 35 to 42, wherein the polishing step includes polishing the first cut end surface with an abrasive polishing surface. [Appendix 44] The method of Appendices 43, wherein the abrasive polishing surface comprises abrasive grains having an abrasive grain size no coarser than about 25 μm. [Appendix 45] The method of any one of Appendices 35 to 44, further comprising cooling the first end of the elongated fiber-reinforced composite before and / or during the polishing step. [Appendix 46] An elongated fiber-reinforced composite strength member, at least a first fiber reinforced composite strength element having a longitudinal central axis, the strength element comprising: A coupling matrix; a plurality of reinforcing fibers disposed within the bonding matrix to form a fiber-reinforced composite; at least a first elongated continuous optical fiber embedded within the fiber-reinforced composite and extending from a first end of the strength element to a second end of the strength element; an elongated fiber reinforced composite strength member, at least the first end of the strength element including a first end face, the first end face including the fiber reinforced composite, and a first optical fiber not extending beyond the first end face of the fiber reinforced composite. [Additional Note 47] The strength member of Addition 46, wherein the second end of the strength element includes a second end face, and the first optical fiber does not extend beyond the second end face of the fiber-reinforced composite. [Appendix 48] The strength member of appendix 46 or 47, wherein the strength element includes at least a second elongated, continuous optical fiber embedded within the fiber-reinforced composite, the second optical fiber not extending beyond the first end surface of the fiber-reinforced composite. [Appendix 49] The strength member of Appendix 48, wherein the strength element includes at least a third elongated, continuous optical fiber disposed within the fiber-reinforced composite, the third optical fiber not extending beyond the first end surface of the fiber-reinforced composite. [Appendix 50] The strength member of Appendix 49, wherein the strength element includes at least a fourth elongated, continuous optical fiber disposed within the fiber-reinforced composite, the fourth optical fiber not extending beyond the first end surface of the fiber-reinforced composite. [Addendum 51] A strength member as described in Addendum 49 or 50, wherein the optical fiber is concentrically arranged around the longitudinal central axis of the strength element. [Appendix 52] A strength member described in any one of Appendices 46 to 51, wherein no optical fiber is present along the longitudinal central axis of the strength element. [Appendix 53] A strength member described in any one of Appendices 46 to 52, wherein the optical fiber is a single-mode optical fiber. [Appendix 54] A strength member described in any one of Appendices 46 to 53, wherein the optical fiber is a glass optical fiber. [Appendix 55] The strength member of Appendix 54, wherein the glass optical fiber includes a transparent glass core and a single polymer coating surrounding the transparent glass core. [Appendix 56] The strength member described in Appendices 55, wherein the single polymer coating has an elastic modulus of at least about 1000 MPa. [Appendix 57] A strength member according to any one of Appendices 46 to 56, wherein the strength member has a length of at least about 100 meters. [Appendix 58] The strength member of Appendices 57, wherein the strength member has a length of at least about 3,500 meters. [Appendix 59] A strength member according to any one of Appendices 46 to 58, wherein the strength member has a length of about 7,500 meters or less. [Appendix 60] A strength member as described in any one of Appendices 46 to 59, wherein the strength member is wound on a spool. [Appendix 61] A strength member according to any one of Appendices 46 to 60, wherein the strength member has a substantially circular cross-section. [Appendix 62] The strength member of Appendices 61, wherein the strength member has a diameter of at least about 1.0 mm. [Appendix 63] A strength member as described in Appendices 61 or 62, wherein the strength member has a diameter of about 20 mm or less. [Appendix 64] A strength member described in any one of Appendices 46 to 63, wherein the reinforcing fibers include carbon fibers extending in the longitudinal direction. [Appendix 65] A strength member as described in Appendix 64, further comprising an insulating layer surrounding the carbon fibers. [Appendix 66] The strength member described in Appendix 65, wherein the insulating layer contains glass fibers. [Appendix 67] A strength member as described in appendix 65 or 66, wherein the optical fiber is disposed between the carbon fiber and the insulating layer. [Appendix 68] A strength member described in any one of Appendices 46 to 67, wherein the strength member has a rated tensile strength of at least about 1900 MPa. [Appendix 69] The strength member is about 30 × 10 -6 69. The strength member of any one of claims 46 to 68, having a thermal expansion coefficient of less than or equal to 1 / °C. [Appendix 70] A strength member described in any one of Appendices 46 to 69, wherein a first end surface of the fiber-reinforced composite is a polished surface. [Appendix 71] A strength member described in any one of Appendices 47 to 70, wherein the second end surface of the fiber-reinforced composite is a polished surface. [Appendix 72] A strength member as described in any one of Appendices 46 to 71, wherein the first end surface is substantially perpendicular to a longitudinal central axis of the strength member. [Addendum 73] A strength member described in any one of Addendums 46 to 72, wherein a first end of the first optical fiber is substantially flush with the first end face of the fiber-reinforced composite. [Appendix 74] A strength member as described in any one of Appendices 46 to 73, wherein the strength member comprises a single strength element. [Appendix 75] A strength member as described in any one of Appendices 46 to 73, wherein the strength member comprises a plurality of strength elements. [Appendix 76] An overhead electric cable, A strength member according to any one of appendix 46 to 75; and a conductive layer surrounding said strength members. [Appendix 77] The overhead electrical cable of Appendices 76, wherein the conductive layer includes a plurality of conductive strands disposed about the strength members. [Appendix 78] A device for transmitting light to an end of an optical fiber embedded in an elongated structural member, comprising: a substantially rigid structure; a bore disposed at least partially through the structure and having an opening at a first end of the bore, the opening and the bore configured to receive an end of an elongated structural member having at least a first optical fiber embedded along a length of the structural member; a light source disposed at least partially within the structure and proximate a second end of the bore, the light source configured to transmit light into the bore and toward an end of the elongated member when the elongated member is disposed within the first end of the bore; and a power source operably attached to the light source. [Addendum 79] The device of Addendum 78, wherein the light source is an incoherent light source. 80. The device of claim 79, wherein the light source comprises a light emitting diode (LED). 81. The device of claim 80, wherein the LED is configured to emit light in a wavelength range of at least about 300 nm and up to about 1000 nm. [Addendum 82] The device of Addendum 81, wherein the LED is configured to emit light in a wavelength range of at least about 800 nm and not more than about 900 nm. [Addendum 83] The device described in any one of Addendums 78 to 82, further comprising a motor operably connected to the light source and configured to move the light source when the light source transmits light into the bore. [Additional Note 84] The device of Addition 83, wherein the motor is configured to rotate the light source about a central axis of the light source. [Addendum 85] The device of any one of Addendums 78 to 84, further comprising a stop element for maintaining a distance between the light source and an end of the structural member when the structural member is positioned within the first end of the bore. [Addendum 86] The device of Addendum 85, wherein the stop element includes a shoulder disposed within the bore, the shoulder configured to prevent movement of the structural member past the shoulder in a direction toward the light source. [Appendix 87] The device of Appendices 85 or 86, wherein the stop element is configured to maintain a distance between the end of the structural member and the light source of at least about 0.1 mm and no more than about 150 mm. [Addendum 88] A device described in any one of Addendums 78 to 87, wherein the rigid structure is made of metal. [Appendix 89] The device of Appendices 88, wherein the metal comprises aluminum. [Appendix 90] A device for detecting light emanating from an end of an optical fiber embedded in an elongated structural member, comprising: a substantially rigid structure; a bore disposed at least partially through the structure and having an opening at a first end of the bore, the opening and the bore configured to receive an end of an elongated structural member having at least a first optical fiber embedded along a length of the structural member; a photodetector disposed within the structure proximate to the second end of the bore, the photodetector configured to receive and detect light from the optical fiber when an elongated member is disposed within the first end of the bore; and a power source operably attached to the photodetector. [Addendum 91] The device of Addendum 90, wherein the photodetector is selected from a CCD sensor and a CMOS sensor. [Addendum 92] The device of Addendum 90 or 91, further comprising a light-blocking element disposed at the first end of the bore and configured to seal around the structural member when the structural member is disposed within the bore. [Additional Note 93] The device of Addition 92, wherein the light-blocking element comprises an elastomeric material. [Addendum 94] The device of any one of Addendums 90 to 93, further comprising a stop element configured to maintain a distance between the optical detector and an end of the structural member when the structural member is positioned within the first end of the bore. [Addendum 95] The device of Addendum 94, wherein the stop element includes a shoulder disposed within the bore, the shoulder configured to prevent movement of the structural member past the shoulder toward the photodetector. [Addendum 96] The device of any one of Addendums 94 to 95, wherein the stop element is configured to maintain a distance between the end of the structural member and the photodetector of at least about 5 mm and no more than about 300 mm. [Addendum 97] A device described in any one of Addendums 90 to 96, further comprising a lens configured to focus light emanating from the optical fiber onto the photodetector. [Addendum 98] A device described in any one of Addendums 90 to 97, wherein the rigid structure is made of metal. [Additional Note 99] The device of Additional Note 98, wherein the metal comprises aluminum. [Appendix 100] A cutting and polishing tool, comprising: A planar body, a cutting edge disposed along at least one edge of the planar body; a planar body including a polished surface covering at least a portion of the planar body; an alignment member operably associated with the planar body, the alignment member configured to operably align an elongated structural member having a longitudinal axis to the planar body such that the cutting blade of the planar body is configured to move and cut the elongated structural member substantially perpendicular to the longitudinal axis to form a cut surface, and the polishing surface is configured to polish the cut surface as the cutting blade cuts and moves through the elongated structural member. [Addendum 101] The tool described in Addendum 100, wherein the planar body is substantially circular. [Supplementary Note 102] The tool of Supplementary Note 101, further comprising a motor operably connected to the planar body and configured to rotate the planar body about a central axis of the planar body. [Addendum 103] The tool of any one of Addendums 100 to 102, wherein the cutting edge includes a plurality of cutting teeth. [Appendix 104] The tool of any one of Appendices 100 to 102, wherein the cutting edge includes an abrasive surface. [Appendix 105] The tool of Appendices 104, wherein the abrasive surface comprises abrasive grains having a size of at least about 35 μm. [Addendum 106] The tool of any one of Addendums 100 to 105, wherein the abrasive surface comprises abrasive grains of an abrasive. [Appendix 107] The tool of Appendices 106, wherein the abrasive grains have a size of about 25 μm or less. [Appendix 108] The tool of any one of Appendices 100-107, wherein the abrasive surface is elevated from the surface of the planar body by at least about 0.1 mm and no more than about 1.2 mm. [Appendix 109] The tool of any one of Appendices 100-108, further comprising an actuation mechanism configured to urge the abrasive surface toward an end of the elongated structural member. [Additional Note 110] The tool of Additional Note 109, wherein the actuation mechanism includes a spring. [Addendum 111] The tool described in any one of Addendums 100 to 110, further comprising a battery for powering the movement mechanism of the planar body. [Addendum 112] The tool of Addendum 111, wherein the battery has a voltage of about 18 volts or less. [Addendum 113] The tool of any one of Addendums 100 to 111, wherein the tool is a handheld tool having a gripping member for holding and freely manipulating the tool. [Addendum 114] The tool of any one of Addendums 100 to 113, further comprising a capture mechanism configured for capture of dust from the cutting and polishing steps. [Appendix 115] A method of manufacturing an elongated fiber-reinforced composite strength element configured for use in a tensile strength member, comprising the steps of: forming an elongated fiber-reinforced composite having a longitudinal central axis, the fiber-reinforced composite including a bonding matrix and a plurality of reinforcing fibers disposed within the bonding matrix; embedding at least a first optical fiber in the fiber-reinforced composite during the step of forming the fiber-reinforced composite, the first optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite; cutting the fiber-reinforced composite adjacent a first end of the fiber-reinforced composite, the cutting forming a substantially flat first cut end surface; and polishing the first cut end surface to form an elongated fiber reinforced composite strength element having a polished first end surface, the polished first end surface including the fiber reinforced composite and a first end of an optical fiber. [Appendix 116] A step of making a second cut of the fiber-reinforced composite adjacent a second end of the fiber-reinforced composite, the second cut forming a substantially flat second cut end surface; 116. The method of claim 115, further comprising polishing the second cut end surface to form a second polished end surface comprising the fiber-reinforced composite and a second end of the first optical fiber. [Addendum 117] The method of Addendum 115 or 116, further comprising embedding at least a second optical fiber in the fiber-reinforced composite during the step of forming the fiber-reinforced composite, the second optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite. [Addendum 118] The method of Addendum 117, further comprising embedding at least a third optical fiber in the fiber-reinforced composite during the step of forming the fiber-reinforced composite, the third optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite. [Addendum 119] The method of Addendum 118, further comprising embedding at least a fourth optical fiber in the fiber-reinforced composite during the step of forming the fiber-reinforced composite, the fourth optical fiber extending from a first end of the fiber-reinforced composite to a second end of the fiber-reinforced composite. [Addendum 120] The method of Addendum 118 or 119, wherein the optical fiber is concentrically arranged around a central longitudinal axis of the intensity element. [Addendum 121] The method of any one of Addendums 115 to 120, wherein no optical fiber is present along the longitudinal central axis of the strength element. [Addendum 122] The method of any one of Addendums 115 to 121, wherein the strength element has a length of at least about 3,500 meters. [Addendum 123] The method of any one of Addendums 115 to 122, wherein the strength element has a length of about 7,500 meters or less. [Addendum 124] The method of any one of Addendums 115 to 123, further comprising winding the fiber-reinforced composite onto a spool prior to the cutting and polishing steps. [Addendum 125] The method of any one of Addendums 115 to 124, wherein the reinforcing fibers comprise longitudinally extending carbon fibers. [Addendum 126] The method of any one of Addendums 115 to 125, wherein the step of forming the elongated fiber-reinforced composite and embedding the optical fiber includes pulling the reinforcing fiber and the optical fiber through a drawing device. [Addendum 127] The method of any one of Addendums 115 to 126, wherein the step of cutting the fiber-reinforced composite includes cutting with an electrically powered abrasive cutting blade. [Appendix 128] The method of Appendices 127, wherein the abrasive cutting edge comprises abrasive grains having a size of at least about 30 μm. [Addendum 129] The method of any one of Addendums 127 to 128, wherein the powered abrasive cutting blade is rotated by a motor during the cutting step. [Addendum 130] The method of any one of Addendums 127 to 129, further comprising the step of fixing a first end of the fiber-reinforced composite such that the first end is positioned substantially perpendicular to a cutting blade during the cutting step. [Addendum 131] The method of Addendum 130, wherein the polishing step includes polishing the first cut end surface with a polishing surface. [Appendix 132] The method of Appendices 131, wherein the polishing surface comprises polishing grains having an abrasive grain size of about 25 μm or less. [Addendum 133] The method of any one of Addendums 115 to 132, further comprising cooling the first end of the fiber-reinforced composite before and / or during a polishing step.

Claims

1. A system configured for detecting a break in an elongated fiber reinforced composite strength member configured for use in an overhead electrical cable, comprising:

1. An elongated fiber reinforced composite strength member having a tensile strength of at least 1900 MPa, the strength member being formed from a single fiber reinforced composite strength element having a circular cross section and a central longitudinal axis, the strength element comprising: A coupling matrix; a plurality of substantially continuous reinforcing fibers operatively arranged within said bonding matrix to form a fiber-reinforced composite; the elongated fiber reinforced composite strength member including at least three optical fibers embedded within the strength element and extending from a first end of the strength element to a second end of the strength element, the at least three optical fibers being spaced apart from and disposed about the central axis of the strength element, the first and second ends of the strength element each comprising a smooth planar surface, and the at least three optical fibers not extending beyond the smooth planar surfaces of the first and second ends of the strength element; an optical transmission device operably connected to a first end of the strength member, the optical transmission device including an incoherent light source operably connected to a power source and configured to transmit incoherent light having a wavelength of at least about 300 nm and less than or equal to about 1700 nm toward the first end of the strength member and into a first end of each of the at least three optical fibers; a light detection device operably connected to a second end of the strength member, the light detection device including a light sensor configured to detect light from the incoherent light source that has passed through the second end of each of the at least three optical fibers.

2. The system of claim 1 , wherein the at least three optical fibers are disposed about and substantially equidistant from the central longitudinal axis of the strength element.

3. The system of claim 2 , wherein the at least three optical fibers are radially spaced at angular intervals of about 120°.

4. 3. The system of claim 1 or 2, wherein the strength element includes a fourth optical fiber embedded within the strength element, the fourth optical fiber being spaced from the central axis and extending from the first end of the strength element to the second end of the strength element, and the fourth optical fiber does not extend beyond the smooth planar surfaces of the first and second ends of the strength element.

5. 5. The system of claim 4, wherein the at least three optical fibers and the fourth optical fiber are disposed about the central longitudinal axis of the strength element and are substantially equidistant from the central longitudinal axis of the strength element.

6. The system of claim 5 , wherein the at least three optical fibers and the fourth optical fiber are radially spaced at angular intervals of approximately 90°.

7. 7. The system of claim 1, wherein the incoherent light source is configured to emit light having a dominant wavelength in the infrared region.

8. 8. The system of claim 1, wherein the incoherent light source is configured to emit light having a dominant wavelength of at least about 800 nm.

9. 9. The system of claim 1, wherein the incoherent light source is configured to emit light having a dominant wavelength of 1000 nm or less.

10. The system of claim 1 , wherein the incoherent light source comprises a light emitting diode (LED).

11. The system of claim 1 , wherein the optical sensor is selected from a CCD sensor and a CMOS sensor.

12. 12. The system of claim 1, wherein the strength members have a length of at least about 500 meters.

13. 13. The system of claim 1, wherein the strength members are wound on spools.

14. 14. The system of claim 1, wherein each of the optical fibers is a single mode optical fiber.

15. 15. The system of claim 1, wherein the strength members have a diameter of at least about 1.0 mm.

16. 16. The system of claim 1, wherein the single strength element has a diameter of about 30 mm or less.

17. 1. A method for investigation of a fiber reinforced composite strength member to detect a break therein, the fiber reinforced composite strength member being configured for use in an overhead electrical cable and having a tensile strength of at least 1900 MPa, the strength member being formed from a single fiber reinforced composite strength element having a circular cross section, the strength element having a first end face and a second end face and including a bonding matrix, a plurality of substantially continuous reinforcing fibers operatively arranged within the bonding matrix to form a fiber reinforced composite, and at least three optical fibers embedded within the strength element and positioned around a longitudinal central axis of the strength element and spaced from the central axis, the at least three optical fibers extending from the first end face of the strength element to the second end face of the strength element, each of the at least three optical fibers including a first end and a second end, polishing the first end surface and the second end surface of the strength element; operably attaching an optical transmission device to a first end of the strength member; operably attaching a light detection device to a second end of the strength member; causing the optical transmission device to transmit incoherent light from a light source operably connected to a power source; and the incoherent light having a wavelength of at least about 300 nm and no greater than about 1700 nm is transmitted toward the first end of the strength member and into the first end of each of the at least three optical fibers; detecting the presence of the incoherent light transmitted by the light source that has passed through the second ends of each of the at least three optical fibers at the second ends of the strength member; the first end face and the second end face of the strength element each comprise a smooth planar surface, and the at least three optical fibers do not extend beyond the smooth planar surfaces of the first end and the second end of the strength element.

18. 20. The method of claim 17, wherein the at least three optical fibers are disposed about and substantially equidistant from the central longitudinal axis of the strength element.

19. 20. The method of claim 18, wherein the at least three optical fibers are radially spaced at angular intervals of about 120 degrees.

20. 20. The method of any one of claims 17 to 19, wherein the strength element includes a fourth optical fiber embedded therein, the fourth optical fiber being spaced from the central axis and extending from the first end face of the strength element to the second end face of the strength element, the fourth optical fiber not extending beyond the smooth planes of the first and second end faces of the strength element.

21. 21. The method of claim 20, wherein the at least three optical fibers and the fourth optical fiber are disposed about and substantially equidistant from the central longitudinal axis of the strength element.

22. 22. The method of claim 21, wherein the at least three optical fibers and the fourth optical fiber are radially spaced at angular intervals of about 90 degrees.

23. 23. A method according to any one of claims 17 to 22, wherein the transmitted incoherent light has a dominant wavelength in the infrared region.

24. 24. The method of any one of claims 17 to 23, wherein the transmitted incoherent light has a dominant wavelength of at least about 800 nm.

25. 25. The method of any one of claims 17 to 24, wherein the transmitted incoherent light has a dominant wavelength of 1000 nm or less.

26. 26. The method of any one of claims 17 to 25, wherein the composite strength member has a length of at least about 500 meters.

27. 27. The method of any one of claims 17 to 26, wherein the composite strength member has a length of at least about 3500 meters.

28. 28. The method of any one of claims 17 to 27, wherein the composite strength member is wound onto a spool.

29. 29. The method of any one of claims 17 to 28, wherein each of the optical fibers is a single mode optical fiber.

30. 30. The method of claim 17, wherein the step of causing the optical transmission device to transmit incoherent light comprises energizing a light emitting diode (LED).

31. The method of claim 17, wherein the light detection device includes a light sensor selected from a CCD sensor and a CMOS sensor.

Images