Method for manufacturing an instrumented strand

Abstract

Method for manufacturing an instrumented strand. The present invention relates to a method for manufacturing an instrumented strand (1) intended for a textile operation for the formation of a fibrous preform of a part made of composite material, comprising: - a scrolling of at least one wire detection element (5) capable of transmitting a physical signal, reinforcing yarns (104; 108) being attached around said at least one scrolling wire detection element so as to form a preform (110) of the instrumented strand, and - a deposition of a binder (111) for holding onto the preform of the instrumented strand thus obtained so as to obtain the instrumented strand. Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for manufacturing an instrumented strand technical field

[0001] The invention proposes the manufacture of a strand equipped with a sensing element intended to undergo a textile operation in order to form a fibrous preform of a part made of composite material, and its applications for the inspection of the preform or the part. Prior art

[0002] Structural Health Monitoring (SHM) aims to maintain and extend the service life of structural components, and to detect and predict their failures. Current techniques typically involve surface instrumentation of the component after its manufacture is complete, by installing gauges, most often temporarily. This instrumentation is limited, particularly in that it does not allow for monitoring the matrix formation stage, which is carried out, for example, by resin transfer molding (RTM). Other techniques propose instrumentation within the material by removing a portion or modifying the textile architecture of the reinforcement to allow for instrumentation installation. These techniques are not entirely satisfactory because they can impact the mechanical strength of the manufactured component. Description of the invention

[0003] The invention relates to a method for manufacturing an instrumented strand intended for a textile operation for the formation of a fibrous preform of a part made of composite material, comprising: - a scrolling of at least one wire detection element capable of transmitting a physical signal, with reinforcing wires being attached around said at least one scrolling wire detection element so as to form a preform of the instrumented strand, and - a deposit of a retaining binder on the preform of the instrumented strand thus obtained so as to obtain the instrumented strand. The strand manufactured according to the invention allows for direct instrumentation of the material during the textile operation of forming the fibrous preform, with minimal impact on textile properties, such as fiber volume percentage or weave structure in the case of a woven preform. The mechanical strength of the part is thus not altered by the instrumentation. Furthermore, it becomes possible to perform monitoring during the matrix formation stage. The strand manufactured according to the invention allows for durable instrumentation throughout the part's lifecycle, both during its manufacture and during its service life. Moreover, the fact that the yarns are brought back Reinforcement around the scrolling detection element helps to prevent undulations in the latter and ensures that it extends in a substantially straight line in the instrumented strand, in order to avoid any risk of damaging it.

[0004] In one embodiment, the added reinforcing wires comprise a first set of reinforcing wires in a first material, and a second set of reinforcing wires in a second material different from the first material.

[0005] Such a feature makes it possible to provide a strand with hybrid reinforcing yarns, improving the performance of the latter.

[0006] In particular, the first material can be glass and the second material carbon.

[0007] The presence of glass fibers can act as a tracer, particularly to aid in positioning the fibrous preform in the injection mold for matrix formation, and the carbon fibers improve the compatibility of the instrumented strand with carbon strands intended to form the rest of the fibrous preform. These materials are particularly well-suited to the manufacture of a turbomachine blower component, but those skilled in the art will recognize that other materials are possible depending on the intended application.

[0008] In one embodiment, the process further includes a formation of the reinforcing wires by separating the wires of a reinforcing strand before the formation of the preform of the instrumented strand.

[0009] Obtaining the reinforcing yarns by opening a reinforcing strand makes it possible to limit the impact of the instrumentation on the diameter of the strand and on the textile to be obtained.

[0010] In one embodiment, the preform of the instrumented strand includes a winding of the reinforcing wires around said at least one wire detection element.

[0011] Such a feature makes it possible to optimally protect the wired detection element.

[0012] In one embodiment, said at least one wire detection element is an optical fiber.

[0013] The use of an optical fiber is preferable because it is suitable for providing a wide variety of information and therefore allows for more flexible control. Other detection methods are nevertheless possible, as will be discussed later.

[0014] In one embodiment, the optical fiber includes a core having at least one Bragg grating optical filter.

[0015] The use of a Bragg grating optical filter makes it possible to give a particularly precise state of the material health of the part or preform.

[0016] The invention also relates to a method for manufacturing a part made of composite material, comprising: - the manufacture of at least one instrumented strand by implementing a process as described above, - the formation of a fibrous preform of the part to be obtained by carrying out one or more textile operations using said at least one instrumented strand, and - the formation of a matrix in a porosity of the fibrous preform. In one example of implementation, the fibrous preform is formed by three-dimensional weaving.

[0017] In one embodiment, the part is a part of a fan of an aircraft engine, such as a fan blade or a fan housing.

[0018] A method for monitoring a physical parameter in a fibrous preform as described above or in a part as described above can be carried out, comprising at least the detection of a possible change in the propagation of the physical signal conducted by the wire detection element using a control unit, and the determination of information relating to the physical parameter from the detection carried out.

[0019] In an example embodiment, the physical parameter is chosen from at least one of: the progression of a matrix material in the porosity of the fibrous preform, the temperature within the fibrous preform during the baking of a matrix material impregnating the fibrous preform, or the application of mechanical stresses in the composite material part. Brief description of the drawings

[0020] [Fig-1] [Fig.1] represents, schematically and partially, an example installation for the manufacture of an instrumented strand according to the invention.

[0021] [Fig.2] [Fig.2] represents, schematically and partially, a section transversal of the instrumented strand produced by the installation of the [Fig.l].

[0022] [Fig. 3] [Fig. 3] represents, schematically, an example of an optical fiber usable in the instrumented strand of [Fig.2].

[0023] [Fig.4] Fig.4 represents relative intensity-wavelength graphs per se to an incident wave at the input of the optical fiber of an instrumented strand usable within the framework of the invention, to the wave transmitted at the output of this optical fiber and to the wave reflected at the input of this optical fiber.

[0024] [Fig. 5] [Fig. 5] schematically represents the length shift wave of the wave reflected at the input of an optical fiber of an instrumented strand usable within the framework of the invention following deformations of this fiber.

[0025] [Fig. 6] [Fig. 6] represents, schematically and partially, a preform fibrous material usable within the framework of the invention.

[0026] [Fig.7] Fig.7 represents, schematically and partially, the monitoring of a physical parameter in a fibrous preform obtained by implementation of the invention.

[0027] [Fig-8] The [Fig.8] represents, schematically and partially, the monitoring of a physical parameter in a part made of composite material obtained by implementing the invention. Description of the implementation methods

[0028] Figure 1 shows an example of an installation 100 for forming an instrumented strand with a wire detection element, here in the form of an optical fiber. The exemplified technique employs a wire commingling technique (known as "commingling" in the English-language literature). Generally, the instrumented strand can be produced by a continuous manufacturing method in which the reinforcing wires are obtained by spreading the constituent wires of a reinforcing strand and are then wrapped around the moving wire detection element. See WO 2016 / 057735, which describes the spreading followed by wire commingling technique.

[0029] The installation 100 exemplified in [Fig. 1] comprises a reel 102 onto which is wound a reinforcing strand, which here is formed of a plurality of glass reinforcing wires 104. The wires 104 are separated from each other by a tension-pulling technique known per se, using a separator roller 103 which, in the illustrated example, has a longitudinal cross-section of varying thickness with a region of increased thickness in its central area. Those skilled in the art will recognize that other roller 103 structures are possible for achieving the spacing of the wires 104. The installation 100 further comprises a reel 101 onto which is wound the optical fiber 5, which is advanced by conveying it through rollers 103 and 109. By way of example, an optical fiber 5 commercially available under the reference "SM1250 Bend Insensitive Polyimide" may be used.The installation includes two guiding devices 105 and 107 for guiding the wires 104 so as to progressively bring them closer to the advancing optical fiber 5. In the illustrated example, the devices 105 and 107 may be in the form of eyelets, possibly rotatable, so as to wind the wires 104 around the optical fiber 5 if desired. The preform 110 of the instrumented strand is formed at the drive roller 109, on which the fiber 5 and the wires 104 are intertwined. The preform 110 of the instrumented strand is driven by the roller 109 into a bath 111 of a retaining binder contained in a reservoir 113. A conveyor element 115 is immersed in the bath to advance the preform 110 through the bath 111. The retaining binder may be polymeric. As an example, bath 111 can be formed by an aqueous solution of a polymer such as polyvinylpyrrolidone (PVP) but . Those skilled in the art will recognize that other compounds can be considered. The preform 110 coated with the retaining binder is then conveyed through an oven 119 by means of the conveying elements 117 and 121 to bake the binder and increase its rigidity so as to obtain the instrumented strand 1 which is then wound around the reel 123 awaiting a textile operation to form the fibrous preform of the part.

[0030] The illustrated example relates to a particular case where a second set of reinforcing wires 108 is interwoven with the wires 104 and the optical fiber 5. The installation includes a reel 106 onto which is wound a second reinforcing strand, which here is formed of a plurality of carbon reinforcing wires 108. The wires 108 are separated by a separator roller 103 and are then guided and wound around the optical fiber 5 as described for the wires 104. The example makes it possible to obtain an instrumented strand 1 with glass and carbon reinforcing wires, the presence of carbon wires improving the mechanical performance of the instrumented strand and reducing heterogeneity with the rest of the fibrous preform of the part to be obtained, which may include carbon strands in the case of a preform for a fan part (blade or casing) of an aircraft engine. Figure [Fig. 2] shows a cross-sectional view of the strand 1 thus obtained.The illustrated example concerns an instrumented strand comprising reinforcing wires made of different materials, but we do not depart from the scope of the invention when reinforcing wires made of the same material are used around the optical fiber 5.

[0031] We have just described a possible technique for the continuous fabrication of a strand instrumented by an optical fiber distinct from the reinforcing wires 104 and 108 and intended for integration into a part made of composite material. The following details a possible structure for the optical fiber 5 in relation to [Fig. 3].

[0032] The illustrated optical fiber 5 comprises a core 50 for transmitting an optical signal, surrounded by a cladding 54 which helps confine the optical signal within the core 50. The cladding 54 and the core 50 are surrounded by a protective coating 56, for example, made of a polymeric material. In the illustrated example, the core 50 comprises at least one optical Bragg grating filter 52 (or several such filters positioned one after the other along the core 50). The optical Bragg grating filter 52 corresponds to a structure known per se in which there is a periodic variation of the refractive index with a pitch p that allows it to reflect a precise wavelength, as will be discussed further below. The optical fiber 5 present in the composite material part or in the preform of this part is intended to be connected to a control unit for tracking.The control unit may include a light source, such as a laser, to send light into the optical fiber. as well as an analyzer for analyzing the reflected optical signal, and in particular for determining its wavelength in order to compare it to the reference wavelength filtered by the optical fiber. The control unit can be located in the turbomachine's fan, or alternatively, connected only for the purpose of performing the control and disconnected once the control is complete. The control unit may include a data storage device for storing information relating to the optical signal passing through the optical fibers for continuous or subsequent analysis.

[0033] Figure 4 shows the effect of the Bragg grating optical filter 52 on an incident light wave having a light intensity distribution IE as a function of the wavelength at the optical fiber input as illustrated in Graph 4A. Graph 4B shows the transmitted light intensity IT as a function of wavelength through the optical filter 52, and Graph 4C shows the reflected light intensity IR by the optical filter 52. The optical filter 52 reflects light at wavelength XB, thus filtering this wavelength with a certain precision, as illustrated in Graph 4C (reference wavelength filtered by the optical fiber). The wavelength reflected by the optical filter 52 is given by the formula below and is provided by the optical fiber manufacturer:

[0034] [Math.l] HAS s =2*n*p

[0035] in this formula n the effective refractive index and p the pitch of the filter.

[0036] Pulling or compressing the optical fiber results in a change in the filter pitch P and, consequently, in the reflected wavelength. There is a linear relationship between the change in wavelength and the change in the filter length 52 (i.e., the deformation) as shown in the formula below. Analysis of the change in XB allows the deformation to be deduced.

[0037] [Math.2]

[0038] Lo denotes the length of the filter 52 enabling the filtering of wavelength XB and the factor k corresponds to the fiber factor provided by the fiber manufacturer. Figure 5 shows the effect on the reflected wavelength of a stress applied to the optical fiber. Graph 5A shows that applying a tensile stress to the fiber results in a shift towards higher wavelengths of the reflected wavelength. Conversely, applying a compressive stress results in a decrease in the reflected wavelength (graph 5B). The remainder of the Light is directed to the end of the optical fiber to prevent interference with the measurement. From the wavelength shift of the optical signal reflected by the fiber, the fiber's deformation is then deduced. This deformation allows, if desired, the stress at filter 52 to be determined. For example, several Bragg grating optical filters 52 with different pitches can be connected in series to distinguish the signals reflected by each filter. This allows the application of stress or deformation to be localized along the fiber. Optical filters can also be used to create pressure or acceleration sensors.The temperature applied to the preform can also be measured, for example during matrix formation, or to the part due to a change in the refractive index of the optical fiber, resulting in a modification of the propagation of the optical signal. In the case of using a Bragg grating filter, this also results in a modification of the reflected wavelength. Examples of monitoring possibilities offered by the instrumented strand on a composite material part and its preform will be described below.

[0039] A fibrous preform 10 of the part to be obtained can be formed by three-dimensional weaving from a plurality of strands 1 described above ([Fig. 6]). The invention is not limited to this case, and the fibrous preform can alternatively be obtained by two-dimensional weaving or braiding of the strands 1. In the example of [Fig. 6], the preform 10 comprises a plurality of strands 1 present in both the warp direction CH and the weft direction TR, but this does not depart from the scope of the invention if it is otherwise. A fibrous preform can be formed solely from strands 1 as described above, or with a mixture of these strands 1 with separate strands lacking the element 5. Generally, the position of the strand(s) incorporating the element 5 is chosen according to the physical parameter to be monitored. In addition, care can be taken to ensure that the instrumented strand(s) are visible from a surface of the preform 10.This can, in the case of using glass reinforcing yarns with a tracer function, help to position the fibrous preform in the mold into which the matrix material is to be fed. During weaving, element 5 is integrated into the preform 10 as the strand 1 to which it belongs is woven.

[0040] Examples of monitoring physical parameters on a fibrous preform 10 or on a part made of composite material 40 are illustrated in relation to figures 7 and 8.

[0041] In the case of [Fig. 7], the aim is to track the progression of a matrix material 30 within a porosity of the preform 10. In order to densify it, the preform 10 is positioned in a mold 20 comprising a form 22 and a counter-form 24, delimiting between them at least one orifice 26 for the introduction of the matrix material 30. The matrix material 30 is introduced along the materialized directionThe material is introduced by arrow IM through orifice 26, for example by injection, and penetrates the porosity of the preform 10. Generally, the matrix material 30 can be a resin, and the resin introduced into the porosity of the fibrous preform can then be cured to obtain a part made of an organic matrix composite material. The advance front of the material 30 in the porosity of the preform 10 is represented by the reference F in [Fig. 7]. The optical fiber 5 is connected to a control unit U by a link 50. The signal from the control unit U can be transmitted and analyzed by a computer, which can then return a result providing information on the progress of the front F.Optical fiber 5 comprises, in a manner known per se, a core forming the conductive portion capable of transmitting an optical signal along the longitudinal axis of the fiber, and a cladding that surrounds the core and contributes to confining the optical signal within the core. The presence of material 30 around optical fiber 5 leads to a modification of the propagation of the optical signal in the conductive portion of fiber 5. Techniques for detecting such a modification of the propagation of the optical signal are known per se. Optical fiber 5 may, for example, include one or more Bragg gratings, and the detection of the modification of the optical signal can be carried out by analyzing the spectral response in transmission or reflection.

[0042] Figure 8 illustrates an example of monitoring a finished part 40. It depicts a fan blade 40, which conventionally comprises a root zone 44, an airfoil zone 42, and a tip 46. The blade 40 also defines a leading edge BA (upstream edge relative to the airflow in the fan) and a trailing edge BF (downstream edge relative to the airflow in the fan). The control unit U is connected to the optical fiber 5 in the same way as in Figure 7. Continuous monitoring can be performed, particularly during the operation of the blade 40, or the control unit U can be connected to the optical fiber 5 to perform the monitoring and then disconnected once the monitoring is complete. In the example considered, the evolution of the mechanical stresses applied in part 40 during operation is monitored by detecting a change in the propagation of the optical signal transmitted by the optical fiber 5.A technique similar to that described above can enable the detection of such a modification. The invention can also be applied to the manufacture of a turbomachine blower housing in composite material, or to other parts. More generally, the application examples in Figures 7 and 8 implement an optical fiber, but those skilled in the art will recognize that other elements 5 can be considered, such as a thermocouple, enabling, in particular, temperature monitoring within the preform during the curing cycle of the material 30, an electrical conductor whose resistance or resistivity can be altered, or a dielectric sensor. These other elements can be used in al- . alternative or in combination with fiber optics.

Claims

Demands

1. Method of manufacturing an instrumented strand (1) intended for a textile operation for the formation of a fibrous preform (10) of a part in composite material, comprising: - a scrolling of at least one wire detection element (5) capable of transmitting a physical signal, reinforcing wires (104; 108) being attached around said at least one scrolling wire detection element so as to form a preform (110) of the instrumented strand, and - a deposition of a retaining binder (111) on the preform of the instrumented strand thus obtained so as to obtain the instrumented strand.

2. A method according to claim 1, wherein the added reinforcing wires comprise a first set of reinforcing wires (104) in a first material, and a second set of reinforcing wires (108) in a second material different from the first material.

3. A method according to claim 2, wherein the first material is glass and the second material is carbon.

4. A method according to any one of claims 1 to 3, wherein the method further comprises forming the reinforcing wires (104; 108) by separating the wires of a reinforcing strand before forming the preform (110) of the instrumented strand.

5. A method according to any one of claims 1 to 4, wherein the instrumented strand preform (110) comprises a winding of the reinforcing wires (104; 108) around said at least one wire sensing element (5).

6. A method according to any one of claims 1 to 5, wherein said at least one wire detection element (5) is an optical fiber.

7. Method according to claim 6, wherein the optical fiber (5) comprises a core (50) having at least one Bragg grating optical filter (52).

8. A method for manufacturing a part (40) of composite material, comprising: - manufacturing at least one instrumented strand (1) by implementing a method according to any one of claims 1 to 7, - forming a fibrous preform (10) of the part to be obtained by carrying out one or more textile operations using said at least one instrumented strand, and - forming a matrix in a porosity of the fibrous preform.

9.

10. Method according to claim 8, wherein the fibrous preform (10) is formed by three-dimensional weaving. Method according to claim 8 or 9, wherein the part (40) is a part of a fan of an aircraft engine.

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