GB2378995A

GB2378995A - Composite material

Info

Publication number: GB2378995A
Application number: GB0215412A
Authority: GB
Inventors: Mark Raymond Steele; Arshad Choudry
Original assignee: Advanced Composites Group Ltd
Current assignee: Cytec Industrial Materials Derby Ltd
Priority date: 2001-08-15
Filing date: 2002-07-04
Publication date: 2003-02-26
Anticipated expiration: 2022-07-04
Also published as: GB0215412D0; GB2378995B; GB0119875D0

Abstract

Composite material 10 for use in bridging a gap between two components A and B, the material comprising a body 12 of fibrous material 14 at least partially impregnated with resinous material 16 and having a compressible structure such that when the material 10 is squeezed between components A and B the fibrous material 14 is compressed. A method of forming a shim of the composite material between two components is also disclosed.

Description

Composite Materials The present invention relates to composite materials and particularly but not exclusively to composite shimming materials.

Shimming materials are used to bridge or substantially bridge gaps usually between two or more components of an assembly. Of particular interest to the present invention is the bridging of gaps or voids between components comprising composite material, such as reinforced resinous material wherein the gaps or voids may be as a result of the manufacturing process of the components.

A known method of shimming or bridging such gaps is to apply liquid resin to one of the components and then to offer the other component thereto to squeeze the resin therebetween. However, this method suffers from a number of disadvantages. The shim produced in this way can act to irreversibly stick the two components together and often has significantly different physical characteristics to the components. The application of the material is also often messy and inconvenient.

According to the present invention there is provided composite material for use in bridging a gap between components, the material comprising a body of fibrous material at least partially impregnated with resinous material and having a compressible structure such that when the material is squeezed between the components the fibrous material is compressed.

Preferably, the impregnated fibrous material is substantially devoid of air voids. In the preferred embodiment, the volume of the fibrous material after compression is substantially the same as its volume before compression.

Preferably the composite material can be compressed by up to between 20% and 70% of the resting thickness thereof, the resting thickness being the thickness of the material at rest and prior to compression. Desirably the

composite material may be compressible by up to approximately 50% of the resting thickness.

Preferably the fibrous material comprises up to 25% of the composite material by weight, and desirably between 5% and 15% by weight.

Preferably the fibrous material comprises a non-woven structure and desirably comprises a random mat fibrous material. Alternatively or in addition the fibrous material may comprise woven and/or partially woven material.

Preferably the resinous material is soaked into the fibrous material. The resinous material may include one or more of an epoxy phenol novolak, epoxy novolak, epoxy cresol novolak, bis phenol A based epoxy resin, bis phenol F epoxy resin, multifunctional epoxy resin, phenolic, cyanate ester, BMI, polyester or any other suitable thermosetting material. The resinous material may further comprise one or more additives such as a thermoplastic, flame retardant, filler and/or curing agent.

Preferably the composite material further comprises a layer on one side which layer is preferably tacky, but less so than the body whereby to facilitate use of the material, in particular application of the material to a component.

The layer may be resinous and may comprise one or more of epoxy phenol novolak, epoxy novolak, epoxy cresol novolak, bis phenol A based epoxy resin, bis phenol F epoxy resin, multifunctional epoxy resin, phenolic, cyanate ester, BMI, polyester and/or, other thermosetting material (s). The layer may further comprise one or more additives such as thermoplastic, flame retardant, filler and/or curing agent. The viscosity of the layer is desirably considerably greater at substantially room temperature, than the viscosity of the resinous material of the body.

The body may be substantially planar, and may be in the form of sheet.

The said layer may be provided on at least one side of the body.

The composite material may comprise one or more releasable layers. A releasable layer may comprise a substantially non-tacky material, such as paper or the like releasably attached to the body and/or said layer (s).

Preferably the composite material is at least partially curable at temperatures up to in the order of 1200, more preferably at temperatures up to in the order of 60T and desirably substantially at room temperature thereby obviating the need for heat to be applied to cure or part cure the material between components.

Preferably the material is further curable after the aforementioned curing step at temperatures up to in the order of 1800C, and desirably up to, or at, a temperature in the order of 120 C.

Preferably the material can be cut or otherwise formed into a desired shape for use.

According to a further aspect of the present invention there is provided a method of forming a shim between components using composite material substantially as described in any of the preceding ten paragraphs, the method comprising locating and compressing the composite material between the components.

Preferably the material is cut or formed into a desired shape and desirably generally a desired shape of shim prior to mounting.

Preferably the material is mounted on one of said components at a position at which the shim is required to be formed. Preferably the or one of said layers is used to mount the material. If a releasable layer is provided on the said layer this is preferably removed before mounting.

Preferably a releasable layer on the other side of the body is retained in position during formation of a shim whereby to facilitate selective parting of

components when the shim is formed. This enables further working of the shim if appropriate.

Preferably pressure is applied between the components to cause compression of the material therebetween. Preferably excess material extending from between the components is removed.

Preferably the material is compressed by up to 20% to 70% of the thickness thereof and desirably by up to approximately 50% of its resting thickness.

Preferably the material is allowed to cure or partially cure at

temperatures up to in the order of 120 C, desirably at temperatures up to in the order of 60'C, between the components.

Preferably the material further undergoes a further curing step after the aforementioned curing step at temperatures up to in the order of 180 C, and desirably up to, or at, a temperature in the order of 120 C.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which : Fig. 1 is a diagrammatic cross-section of composite material according to the present invention; and Fig. 2 is a diagrammatic illustration of a shim formed using the material of Fig. 1.

Referring to the drawings there is provided composite material 10 for use in bridging a gap between two components A and B (Fig. 2), the material 10 comprising a body 2 of fibrous material 14 at least partially impregnated with resinous material 16 and having a compressible structure such that when the material 10 is squeezed between the components A and B the fibrous material

14 is compressed.

In more detail, the body 12 comprises a mat of non-woven fibrous material 14, which may comprise glass fibre, carbon fibre or any other suitable reinforcement material which is soaked ideally to be fully impregnated, and substantially devoid of air voids, with a relatively low viscosity resinous material 16 comprising one or more of an epoxy phenol novolak, epoxy novolak, epoxy cresol novolak, bis phenol A based epoxy resin, bis phenol F epoxy resin, multifunctional epoxy resin, phenolic, cyanate ester, BMI, polyester and/or any other suitable thermosetting material (s).

Products that have been identified as particularly suitable for the resinous material I6 include Araldite MY 9512 supplied by Vantico Ltd. , MTM 57 prebend manufactured by Advanced Composites Group Limited, LY 1556 supplied by Vantico Ltd. and DY 070 supplied by Vantico Ltd. These are provided in the material in the ratio 50: 25: 25: 6 by weight.

A tack modifying layer 18 is provided on one surface of the generally planar body 12. The tack modifying layer 18 is a resin and comprises one or more of an epoxy phenol novolak, epoxy novolak, epoxy cresol novolak, bis phenol A based epoxy resin, bis phenol F epoxy resin, multifunctional epoxy resin, phenolic, cyanate ester, BMI, polyester or any other suitable thermosetting material (s).

The viscosity of the layer 18 is considerably greater than the viscosity of the resinous material in the body 12, thereby effectively acting to modify the tackiness of one side of the body 12, to facilitate application of the material 10, as will be described.

One particular formulation of the material for the layer 18 is a mixture of EPN 1138 supplied by Vantico Ltd. , Phenotohto YP 50 supplied by Thomas Swan & Co. Ltd. and Curimid CN supplied by Cornelius Chemical Company Ltd. in the ratios 100: 10: 4 by weight.

To both sides of the composite formed by the body 12 and the layer 18 are provided layers 20, 22 of release paper which facilitate the handling of the material 10 both prior to and during use.

In use, the material 10 is used to produce a shim bridging a gap G between two components A and B. The invention has many applications, but applications of particular interest are in the use of forming shims or bridges between two or more components comprising fibre reinforced composite materials, for example in the aerospace, automotive industries and the like.

Often, the manufacturing processes for composite components mean that two components A, B that are required to lie adjacent to each other often have a small gap G therebetween, and it is necessary to bridge this gap using a shim.

In use, a sheet of material 10 can be cut either accurately or approximately to the desired shape of shim required. The provision of the release papers 20, 22 facilitate in the handling and also storage of the material 10.

To form shims, the release paper 20 is removed from the tack modifying layer 18 and the material 10 offered up to one of the components, tack modifying layer 18 first, such that the tack modifying layer 18 sticks to the component, in this example component A to locate and hold the shim material 10 in position.

The second component B is then offered up in the desired position against the release paper 22 (which is retained on the material 10 during shim formation) and the two components A and B compressed together using conventional pressure techniques to cause the body 12 to be compressed. As the body 12 is compressed excess resinous material 16 extending from between the components A, B can be removed, the volume of the fibrous material 14 after compression of the body 12 being substantially the same as the volume of

the fibrous material 14 before compression of the body 12. It will be appreciated as illustrated in Fig. 2, that the shim material will compress to varying degrees depending upon the contours of the surfaces of the components A and B between which it is sandwiched.

When under compression, the material 10 is left to cure, preferably at room temperature. However, it will appreciated that the material may cure at any suitable temperature within the scope of the present invention, but desirably below GOT to facilitate the shim formation process.

The material 10 may be subjected to a further curing, or post curing step after the initial curing step mentioned above. This post curing step allows the material to fully develop its glass transition temperature, the glass transition temperature governing the maximum operating temperature of the material.

This post curing step may take place at temperatures up to 180 C, and desirably up to, or at, 1200C.

Once the material 10 has cured, or partially cured to the desired extent, and has been subjected to the post curing step if desired, the component B can be removed, removal thereof being facilitated by the provision of the release paper 22 which prevents the body 12 from sticking to the component B.

With the component B removed, the shims can be further worked, if necessary, including removal of the release paper 22.

It will be appreciated that the provision of a composite material 10 of the present invention provides for improved formation of shims between components.

Various modifications may be made without departing from the spirit or scope of the present invention. For example, the fibrous material 14 may as an alternative or in addition comprise woven and/or partially woven material.

A tack modifying layer 18 may be provided on more than one surface of the body 12, and possibly ideally on both sides of a planar body.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS 1. Composite material for use in bridging a gap between components, the material comprising a body of fibrous material at least partially impregnated with resinous material and having a compressible structure such that when the material is squeezed between the components the fibrous material is compressed.
2. Composite material as described in claim 1, in which the impregnated fibrous material is substantially devoid of air voids.
3. Composite material as described in any of the preceding claims, in which the volume of the fibrous material after compression is substantially the same as its volume before compression.
4. Composite material as described in any of the preceding claims, in which the composite material can be compressed by up to between 20% and 70% of the resting thickness thereof, the resting thickness being the thickness of the material at rest and prior to compression.
5. Composite material as described in any of the preceding claims, in which the composite material is compressible by up to approximately 50% of the resting thickness.
6. Composite material as described in any of the preceding claims, in which the fibrous material comprises up to 25% of the composite material by weight
7. Composite material as described in claim 6, in which the fibrous material comprises between 5% and 15% of the composite material by weight.
8. Composite material as described in any of the preceding claims, in which the fibrous material comprises a non-woven structure.

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9. Composite material as described in claim 8, in which the fibrous material comprises a random mat fibrous material.
10. Composite material as described in any of the preceding claims, in which the fibrous material comprises woven and/or partially woven material.
11. Composite material as described in any of the preceding claims, in which the resinous material is soaked into the fibrous material.
12. Composite material as described in any of the preceding claims, in which the resinous material includes one or more of an epoxy phenol novolak, epoxy novolak, epoxy cresol novolak, bis phenol A based epoxy resin, bis phenol F epoxy resin, multifunctional epoxy resin, phenolic, cyanate ester, BMI, polyester or any other suitable thermosetting material.
13. Composite material as described in any of the preceding claims, in which the resinous material comprises one or more additives such as a thermoplastic, flame retardant, filler and/or curing agent.
14. Composite material as described in any of the preceding claims, in which the composite material further comprises a layer on one side.
15. Composite material as described in claim 14, in which the layer is tacky, but less so than the body whereby to facilitate use of the material, in particular application of the material to a component.
16. Composite material as described in claim 14 or claim 15, in which the layer is resinous.
17. Composite material as described in claim 16, in which the layer comprises one or more of epoxy phenol novolak, epoxy novolak, epoxy cresol novolak, bis phenol A based epoxy resin, bis phenol F epoxy resin, multifunctional epoxy resin, phenolic, cyanate ester, BMI, polyester and/or,

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other thermosetting material (s).
18. Composite material as described in any of claims 14 to claim 17, in which the layer further comprises one or more additives such as thermoplastic, flame retardant, filler and/or curing agent.
19. Composite material as described in any of claims 14 to 18, in which the viscosity of the layer is considerably greater at substantially room temperature, than the viscosity of the resinous material of the body.
20. Composite material as described in any of the preceding claims, in which the body is substantially planar.
21. Composite material as described in claim 20, in which the body is in the form of sheet.
22. Composite material as described any of claims 14 to 21, in which the said layer is provided on at least one side of the body.
23. Composite material as described in any of the preceding claims, in which the composite material comprises one or more releasable layers.
24. Composite material as described in claim 23, in which a releasable layer comprises a substantially non-tacky material, such as paper or the like

releasably attached to the body and/or said layer (s).
25. Composite material as described in any of the preceding claims, in which the composite material is at least partially curable at temperatures up to in the order of 1200.
26. Composite material as described in claim 25, in which the material is at least partially curable at temperatures up to in the order of 60 C.

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27. Composite material as described in claim 26, in which the material is at least partially curable at room temperature thereby obviating the need for heat to be applied to cure or part cure the material between components.
28. Composite material as described in any of claims 25 to 27, in which the material is further curable after the aforementioned curing step at temperatures up to in the order of 1800C.
29. Composite material as described in claim 28, in which further curing is at temperatures up to, or at, a temperature in the order of 1200C.
30. Composite material as described in any of the preceding claims, in which the material can be cut or otherwise formed into a desired shape for use.
31. A method of forming a shim between components using composite material substantially as described in any of the preceding claims, the method comprising locating and compressing the composite material between the components.
32. A method as defined in claim 31, in which the material is cut or formed into a desired shape and desirably generally a desired shape of shim prior to mounting.
33. A method as described in any of claims 31 or 32, in which the material is mounted on one of said components at a position at which the shim is required to be formed.
34. A method as described in claim 33, in which the or one of said layers is used to mount the material.
35. A method as described in any of claims 31 to 34, in which releasable layer on the said layer is removed before mounting.

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36. A method as described in any of claims 31 to 35, in which a releasable layer on the other side of the body is retained in position during formation of a shim whereby to facilitate selective parting of components when the shim is formed.
37. A method as described in any of claims 31 to 36, in which pressure is applied between the components to cause compression of the material therebetween.
38. A method as described in claim 37, in which excess material extending from between the components is removed.
39. A method as described in claim 37 or claim 38, in which the material is compressed by up to 20% to 70% of the thickness thereof and desirably by up to approximately 50% of its resting thickness.
40. A method as described in any of claims 31 to 39, in which the material is allowed to cure or partially cure at temperatures up to in the order of 120 C, desirably at temperatures up to in the order of 600C, between the components.
41. A method as described in claim 40, in which the material further undergoes a further curing step after the aforementioned curing step at temperatures up to in the order of 1800C, and desirably up to, or at, a temperature in the order of 120 C.
42. Composite material substantially as hereinbefore described with reference to the accompanying drawings.
43. A method substantially as hereinbefore described with reference to the accompanying drawings.
44. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should

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be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.