Composite structure with a structural health monitoring sensor

Abstract

The invention relates a composite panel (2), a first laminate (3) and a second laminate (4) that consist of at least one layer and are positioned opposite each other on the composite panel (2), a gap (5) that is located between the surfaces of the composite panel (2) and the first laminate (3) and the second laminate (4) facing one another and extends along the direction in which the first laminate (3) and the second laminate (4) extend, and at least one filler (6) that ensures that the gap (5) is almost completely filled.

Description

[0001] COMPOSITE STRUCTURE WITH A STRUCTURAL HEALTH MONITORING SENSOR

[0002] This invention is related to composite structures with monitoring sensors that enable the monitoring of structural health status of composite structures and the detection of structural defects.

[0003] Fibre optic sensors are used for the non-destructive inspection of composite structures. Fibre Bragg Grating (FBG) based sensors are a fibre optic sensor technology used in the measurement of strain amounts of structures. FBG sensors are preferred because they are lighter than normal strain gage structures, provide ease of installation and provide more durability on the structures they are used in. FBG sensors provide strain measurement by being embedded in the composite structure. Non-destructive damage inspection can be performed in the composite structure according to the back reflection and transmission parameters of the waves sent by the user via the FBG sensors positioned in the composite structure. The location of the FBG sensors in the composite structure relative to the layers is important for the strength of the composite structure and the accuracy of the non-destructive inspection.

[0004] In the United States patent document numbered US10399286B2 in the state of the art, a fibre Bragg grating sensor positioned in composite materials and the manufacturing method of this structure are mentioned. In said patent document, it is explained that the Fibre Bragg Grating sensor is positioned by embedding it in the structural part or by means of external fixing process. In addition, it is mentioned in said patent document that the composite material is packaged with the composite material in a way that it will not be damaged by the external forces it will be exposed to during the operation while the damage detection is performed on the fibre Bragg grating sensor and in a way that the sensors maintain their strength within the composite structure against external forces.

[0005] By means of the composite structure with structural health monitoring sensor developed with the present invention, the damage status and structural health detections of the composite materials are monitored more effectively and simultaneously by the user or the manufacturer for a long time. By means of the composite structure with structural health monitoring sensor developed with this invention, it is ensured that the composite materials with sensors inside continue their operations without any loss of strength.

[0006] The composite structure with structural health monitoring sensor defined in the first claim and the claims dependent on this claim, which is realised to achieve the aim of the invention, comprises a first laminate that is positioned on the composite panel by the manufacturer, and a second laminate that is positioned partially opposite the first laminate and the composite panel. As a result of the positioning of the surfaces of the first laminate and the second laminate in an almost L-shaped manner on the composite panel, almost perpendicular to the ground and opposite each other, a gap is formed between the surfaces of the first laminate, the second laminate and the composite panel facing one another. The gap is located between the facing surfaces of the first laminate, the second laminate and the composite panel along the direction in which the first laminate and the second laminate extend on the composite panel. The composite structure with structural monitoring sensor comprises at least one filler that allows the gap to be filled and is pre-positioned into the gap by the manufacturer.

[0007] The composite structure with structural health monitoring sensor, which is the subject of the invention, comprises a fibre optic sensor, which is at least one fibre Bragg grating (FBG) sensor embedded in the filler by the manufacturer in a way that it extends in the filler along the direction in which the filler extends in the gap. The structural health monitoring of the composite panel, first laminate and second laminate that are located along the direction in which the filler extends is provided by the data obtained with the waves or signals transmitted and collected back via the fibre optic sensor. The waves or signals transmitted and collected back via the fibre optic sensor by the user may contain data such as structural errors, tension and temperature values that may occur as a result of the loads to which the composite panel, first laminate and second laminate are exposed during operation.

[0008] In one embodiment of the invention, the composite structure with structural health monitoring sensor comprises a filler produced from fabrics with unidirectional fibres (UD) that are preimpregnated with resin in a way that is compatible with the gap and placed in the gap. There are multiple fibres positioned by the manufacturer in the filler structure in order to allow the filler to carry loads. Fibre optic sensors are embedded in the filler in a way that they extend in the same direction and are parallel to the fibres in the structure of the filler. In this way, while structural health monitoring is carried out by the sensor, the loss of the strength properties of the filler is prevented. In one embodiment of the invention, the composite structure with structural health monitoring sensors comprises at least one table (T) on which the filler is laid and the fibre optic sensors are positioned in the same direction as the UD fibres on the filler. At least one mandrel, which is positioned on the filler by the user and has a hollow structure that allows the fibre optic sensors to be placed inside, is used. By means of the mandrel, the filler laid on the table is wrapped in a cylindrical form and when the filler takes cylindrical form, the fibre optic sensor is placed inside the filler in a way that it extends along the filler. A female mould and a male mould are used in order to make the filler, which has a fibre optic sensor embedded in it and is brought to cylindrical form by the manufacturer with the help of a mandrel, compatible with the gap geometry. The filler in cylindrical form is positioned on the female mould that is located on the table by the manufacturer. As a result of the movement of the male mould and female mould towards each other, the filler in cylindrical form is brought to the geometry that will be suitable for the gap geometry under temperature and pressure.

[0009] In one embodiment of the invention, the composite structure with structural health monitoring sensor comprises a first laminate and a second laminate positioned on the composite panel in a way that at least one outer surface is in an angled form. A gap is formed as a result of the first laminate and the second laminate, which have at least one outer radius surface, being positioned on the composite panel in a way that they are opposite each other and the composite panel.

[0010] In one embodiment of the invention, the composite structure with structural health monitoring sensor comprises at least one first mould on which the first laminate is laid by the manufacturer and at least one second mould on which the second laminate is laid, which allow the first laminate and the second laminate to be shaped and cured in a predetermined geometry on the composite panel. The first mould and the second mould allow the first laminate and the second laminate to be shaped on the composite panel in an almost L-shaped manner.

[0011] In one embodiment of the invention, the composite structure with structural health monitoring sensor comprises a filler placed by the manufacturer in the gap in a way that almost completely fills the gap, thus preventing delamination into the gap. Composite panel is produced as a composite stringer by curing the first laminate, second laminate and filler, which are positioned on the composite panel, together or separately.

[0012] In one embodiment of the invention, the composite structure with structural health monitoring sensor comprises filler produced from pre-resin impregnated fabric (pre-preg) consisting of carbon fibre reinforcement and same direction (UD) fibres predetermined by the manufacturer. In one embodiment of the invention, the composite structure with structural health monitoring sensor comprises filler containing fibre optic sensor in order to monitor the structural health status of structural parts that are located on aircraft and / or spacecraft.

[0013] In one embodiment of the invention, the composite structure with structural health monitoring sensor allows the user to monitor the structural health of structural parts, which are located on aircraft and / or spacecraft and which are composite stringers, during their operational states. A fibre optic sensor with reference wavelength or signal characteristic values is positioned inside the filler according to the strength values of the composite stringers during their use on the aircraft. During the use of composite stringers on aircraft and / or spacecraft, the structural health status of the composite stringer is simultaneously monitored according to the reflection and scattering rates of optical waves and / or signals transmitted along the composite stringers by the user or a source previously determined by the user, via the fibre optic sensor.

[0014] In one embodiment of the invention, the composite structure with structural health monitoring sensor comprises a composite stringer preferably produced in a T-form to be suitable for the structural parts on the aircraft and / or spacecraft. The T-form is formed by curing the composite panel first laminate and the second laminate together or separately (co-curing or co-bonding) by means of the first mould and the second mould suitable for the T-form.

[0015] The composite structure with structural health monitoring sensor realised to achieve the aim of the present invention is shown in the attached figures, and of these figures;

[0016] Figure 1 is a perspective view of the composite panel, first laminate, second laminate and filler.

[0017] Figure 2 is a front view of the male mould, female mould, filler and fibre optic sensor.

[0018] Figure 3 is a perspective view of the composite stringer.

[0019] Figure 4 is a top view of the filler, mandrel and table.

[0020] Figure 5 is a front view of the filler.

[0021] Figure 6 is a front view of the first mould and second mould.

[0022] The parts in the figures are numbered one by one and the equivalents of these numbers are given below. 1 . Composite structure with structural monitoring sensor

[0023] 2. Composite panel

[0024] 3. First laminate

[0025] 4. Second laminate

[0026] 5. Gap

[0027] 6. Filler

[0028] 7. Fibre optic sensor

[0029] 8. Mandrel

[0030] 9. Female mould

[0031] 10. Male mould

[0032] 11 . First mould

[0033] 12. Second mould

[0034] 13. Composite stringer

[0035] (T) Table

[0036] (F) Fibre

[0037] The composite structure with structural health monitoring sensor (1) comprises a composite panel (2), a first laminate (3) and a second laminate (4) that consist of at least one layer and are positioned opposite each other on the composite panel (2), a gap (5) that is located between the surfaces of the composite panel (2) and the first laminate (3) and the second laminate (4) facing one another and extends along the direction in which the first laminate (3) and the second laminate (4) extend, and at least one filler (6) that ensures that the gap (5) is almost completely filled. The composite structure with structural health monitoring sensor (1 ), which is the subject of the invention, comprises at least one fibre optic sensor (7) which is positioned in the filler (6) along the direction in which the filler (6) extends and enables data exchange, enabling structural health status monitoring.

[0038] The first laminate (3) and the second laminate (4) are positioned on the composite panel (2) by the manufacturer in such a way that some of their surfaces will touch each other and some will touch the composite panel (2). After they are positioned in this way, the surfaces of the composite panel (2), the first laminate (3) and the second laminate (4) that face one another but do not touch are formed and a gap (5) is formed on this surface along the direction in which the composite panel (2), the first laminate (3) and the second laminate (4) extend. In order to fill the gap (5) almost completely, the filler (6) is placed inside the gap (5) by the manufacturer. In this way, the production and use of composite structural parts with a predetermined strength is ensured (Figure -1 , Figure -5).

[0039] The fibre optic sensor (7) is positioned inside the filler (6) along the direction in which the filler (6) extends. By means of the data exchange provided via optical waves and / or signals via the fibre optic sensor (7), the structural health status of the composite panel (2), first laminate (3), second laminate (4) and filler (6) during testing or use is monitored by the user.

[0040] In one embodiment of the invention, the composite structure with structural health monitoring sensor (1 ), comprises the filler (6) that is made of fabric with pre-impregnated resin- impregnated fibres (F) in the same direction, and the fibre optic sensor (7) in the form of a wire positioned within the filler (6) in a way parallel to the direction in which the fibres in the filler (6) structure extend. There are multiple fibres (F) positioned by the manufacturer in the filler (6) structure to enable the filler (6) to carry loads. The fibre optic sensor (7) is positioned in the filler (6) in a way that the fibres (F) in the filler (6) structure extend in the same direction. By this way, the fibre optic sensor (7) can be positioned in a way that no structural incompatibility occurs between the fibre (F) structures in the filler (6), and the filler (6), which almost completely fills the gap (5) is prevented from losing strength.

[0041] In one embodiment of the invention, the composite structure with structural health monitoring sensor (1 ) comprises at least one table (T) on which the fibre optic sensors (7) are positioned by the user onto the filler (6) in a way that they extend in the same direction as the fibres in the filler (6) structure, at least one mandrel (8) that has a hollow structure on which the fibre optic sensor (7) can be positioned, and allows the filler (6) to be wound by the user, at least one female mould (9) and at least one male mould (10) that are positioned on the table (T) by the manufacturer and placed on top of each other in a form-compatible manner in order to position the mandrel (8) on the filler (6) so that the fibre optic sensor (7) passes through it, to wind the fibre optic sensor (7) by means of a mandrel (8) in such a way that it is almost completely surrounded by the filler (6) and the filler (6) takes a cylindrical form by the manufacturer and to shape the filler (6), and the filler (6) which is positioned on the female mould (9) by the manufacturer and the male mould (10) is moved towards each other in a way that it touches the female mould (9) and the form is made compatible with the gap (5) geometry with the help of heat and pressure. Fibre optic sensors (7) are positioned by the manufacturer by winding them inside the filler (6) via the mandrel (8). First of all, the fibre optic sensor (7) is positioned by the manufacturer inside the gap (5) that is located inside the mandrel (8) and extends along the mandrel (8). Then, the filler (6), which is a pre-impregnated fabric with resin, is wound on the mandrel (8) by the manufacturer in an almost cylindrical form. After the filler (6) takes a cylindrical form, the mandrel (8) is removed from the filler (6) by the manufacturer, leaving the fibre optic sensor (7) inside the filler (6). In this way, the filler (6) structure, which has the fibre optic sensor (7) extending along its length, is produced. The filler (6) comprising the fibre optic sensor (7) is positioned by the manufacturer on the female mould (9) and is shaped in accordance with the geometry of the gap (5) under temperature and pressure by moving the male mould (10) towards the female mould (9) and contacting it. In this way, the filler (6) is shaped in a geometry that can almost completely fill the gap (5). By means of the filler (6) comprising the fibre optic sensor (7), structural health monitoring can be done by the manufacturer and the user along the gap (5) (Figure 2, Figure -4).

[0042] In one embodiment of the invention, the composite structure with structural health monitoring sensor (1 ) comprises a first laminate (3) having at least one outer surface in the form of a radius, a second laminate (4) having at least one outer surface in the form of a radius, and a first laminate (3) and a second laminate (4) positioned on the composite panel (2) in a way that their outer surfaces in the form of a radius are opposite each other. A gap (5) is formed as a result of the positioning of the outer surfaces in the form of a radius of the first laminate (3) and the second laminate (4) on the composite panel (2) in a way that they are opposite each other.

[0043] In one embodiment of the invention, the composite structure with structural health monitoring sensor (1 ) comprises a first mould (1 1 ) that allows the shaping of the first laminate (3) on the composite panel (2) and on which the first laminate (3) is positioned by the manufacturer, and a second mould (12) that is positioned on the body (2) so that it will be opposite to the first mould (11 ) and on which the second laminate (4) is positioned by the manufacturer, allowing the shaping of the second laminate (4). The first laminate (3) and the second laminate (4) are positioned on the first mould (1 1 ) and the second mould (12), respectively, so that they will be opposite to each other. In this way, the curing process is carried out in order to ensure that the first laminate (3) and the second laminate (4) are placed on the composite panel (2) (Figure 6).

[0044] In one embodiment of the invention, the composite structure with structural health monitoring sensor (1 ) comprises a filler (6) that is positioned by the manufacturer to almost completely cover the gap (5) and thus prevent delamination between the first laminate (3) and the second laminate (4), and a composite stringer (13) produced by curing the first laminate (3), the second laminate (4) and the filler (6) together. The filler (6) that is shaped to suit the geometry of the gap (5) in which the fibre optic sensor (7) is located is positioned by the manufacturer in the gap (5) so as to almost completely fill the gap (5). The composite stringer (13) structure is produced by curing the composite panel (2), the first laminate (3), the second laminate (4) and the filler (6) together or separately (Figure -3).

[0045] In one embodiment of the invention, the composite structure with structural health monitoring sensor (1 ) comprises a filler (6) that is produced from carbon fibre reinforced pre-resin impregnated fabric. The filler (6) can be produced from different types of fibre reinforced fabrics by the manufacturer.

[0046] In one embodiment of the invention, the composite structure with structural health monitoring sensor (1 ) comprises a filler (6) that is used in aircraft and / or spacecraft and comprises a fibre optic sensor (7). The fillers (6) used in aircraft and / or spacecraft structures comprise a fibre optic sensor (7). In this way, structural health monitoring of aircraft and / or spacecraft composite stringers (13) can be provided.

[0047] In one embodiment of the invention, the composite structure with structural health monitoring sensor (1 ) comprises the composite stringer (13) that is positioned as a structural part on the aircraft and / or spacecraft, and fibre optic sensor (7) that is located in the structure of the composite stringer (13) and allows simultaneous monitoring of the strength health status of the composite beam (13) by means of the wave transmitted by the user and is located in the filling (6) with a wavelength predetermined according to the structural errors that may occur by the user. The back reflection or scattering or transmission values of the optical waves and / or signals transmitted by the user to the fibre optic sensors (7) can be compared with the predetermined reference back reflection and scattering values, and the presence and location of structural errors in the composite stringer (13) can be determined. In this way, the features that can be detected such as the structural health conditions and temperature conditions depending on the stress on the composite stringer (13) and the filler (6), first laminate (3), second laminate (4) and composite panel (2) along the direction in which the composite stringer (13) extends on the air and / or space vehicle can be monitored simultaneously by the manufacturer and the user.

[0048] In an embodiment of the invention, the composite structure with structural health monitoring sensor (1 ) comprises a composite stringer (13) produced in a T shape. The composite stringer (13) produced in a T shape is used as an aircraft and / or spacecraft structure.

Claims

CLAIMS1 . A composite structure with structural health monitoring sensor (1 ) comprising a composite panel (2), a first laminate (3) and a second laminate (4) that consist of at least one layer and are positioned opposite each other on the composite panel (2), a gap (5) that is located between the surfaces of the composite panel (2) and the first laminate (3) and the second laminate (4) facing one another and extends along the direction in which the first laminate (3) and the second laminate (4) extend, and at least one filler (6) that ensures that the gap (5) is almost completely filled, characterised by at least one fibre optic sensor (7) which is positioned in the filler (6) along the direction in which the filler (6) extends and enables data exchange, enabling structural health status monitoring.

2. A composite structure with structural health monitoring sensor (1 ) according to Claim 1 , characterised by the filler (6) that is made of fabric with fibres pre-impregnated with resin and of the same direction (F) and the fibre optic sensor (7) in the form of a wire positioned within the filler (6) in a way parallel to the direction in which the fibres in the filler (6) structure extend.

3. A composite structure with structural health monitoring sensor (1 ) according to Claim 1 or Claim 2, characterised by- At least one table (T) on which the fibre optic sensors (7) are positioned by the user on the filler (6) in a way that they extend in the same direction as the fibres in the filler (6) structure,- At least one mandrel (8) with a hollow structure that allows the filling (6) to be wrapped by the user so that the fibre optic sensor (7) can be positioned on it, positioning the mandrel (8) on the filling (6) so that the fibre optic sensor (7) passes through it, winding the fibre optic sensor (7) by means of the mandrel (8) by the manufacturer so that it is almost completely surrounded by the filling (6) inside the filling (6) and the filling (6) becomes cylindrical, and- At least one female mould (9) and at least one male mould (10) positioned on the table (T) by the manufacturer for the purpose of shaping the filling (6) and placed on top of each other in a form-compatible manner, the filling (6) produced by the manufacturer positioned on the female mould (9) and moving the male mould (10) towards each other in a way that it touches the female mould (9) and making the form-compatible with the cavity (5) geometry with the help of heat and pressure.

4. A composite structure with structural health monitoring sensor (1 ) according any of the previous claims, characterised by a first laminate (3) having at least one outer surface in the form of a radius, a second laminate (4) having at least one outer surface in the form of a radius, and a first laminate (3) and a second laminate (4) positioned on the composite panel (2) in a way that their outer surfaces in the form of a radius are opposite each other.

5. A composite structure with structural health monitoring sensor (1 ) according any of the previous claims, characterised by a first mould (11 ) that allows the shaping of the first laminate (3) on the composite panel (2) and on which the first laminate (3) is positioned by the manufacturer, and a second mould (12) that is positioned on the body (2) so that it will be opposite to the first mould (1 1 ) and on which the second laminate (4) is positioned by the manufacturer, allowing the shaping of the second laminate (4).

6. A composite structure with structural health monitoring sensor (1 ) according any of the previous claims, characterised by a filler (6) that is positioned by the manufacturer to almost completely cover the gap (5) and thus prevent delamination between the first laminate (3) and the second laminate (4), and a composite stringer (13) produced by curing the first laminate (3), the second laminate (4) and the filler (5) together.

7. A composite structure with structural health monitoring sensor (1 ) according any of the previous claims, characterised by a filler (6) that is produced from carbon fibre reinforced pre-resin impregnated fabric.

8. A composite structure with structural health monitoring sensor (1 ) according any of the previous claims, characterised by a filler (6) that is used in aircraft and / or spacecraft and comprises a fibre optic sensor (7).

9. A composite structure with structural health monitoring sensor (1 ) according to Claims 6 to 8, characterised by the composite stringer (13) that is positioned as a structural part on the aircraft and / or spacecraft, and fibre optic sensor (7) that is located in the structure of the composite stringer (13) and is located in the filler (6) with a wavelength predetermined according to the structural errors that may occur by the user, and allows simultaneous monitoring of the strength health status of the composite beam (13) by means of the wave transmitted by the user.

10. A composite structure with structural health monitoring sensor (1 ) according to Claims 6 to 9, characterised by the composite stringer (13) produced in a T shape.

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