GB2555438A

GB2555438A - A composite material

Info

Publication number: GB2555438A
Application number: GB1618191.9A
Authority: GB
Inventors: Martin Gaitonde John; Bonaventura Joshua
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2016-10-27
Filing date: 2016-10-27
Publication date: 2018-05-02
Also published as: GB201618191D0

Abstract

A composite material 16 comprising a first layer 18 of dry fibre material orientated at a first angle with respect to a longitudinal reference, a toughening agent and a curable resin matrix and a second layer 20 of dry fibre material substantially aligned with the longitudinal reference and curable resin matrix. The composite may include a third layer 22 comprising fibre material orientated at a second angle to the reference, a toughening agent and curable resin matrix. A similar fourth layer, orientated at a third angle to the reference may be included. Multiple series of the four layers are disclosed with different pattern of layers and/or total number. The fibres are preferably unidirectional continuous fibres and preferably comprise carbon or glass fibres. The toughening agent is preferably a thermoplastic. Aircraft components comprising the composite are claimed. A method is also claimed comprising laying up a first layer of fibre with attached toughening agent, at a first angle, laying up a second layer on the first layer, the fibres arranged in the reference direction and then infusing the stack with a curable resin before applying heat and pressure to form a composite.

Description

(54) Title of the Invention: A composite material Abstract Title: A composite material (57) A composite material 16 comprising a first layer 18 of dry fibre material orientated at a first angle with respect to a longitudinal reference, a toughening agent and a curable resin matrix and a second layer 20 of dry fibre material substantially aligned with the longitudinal reference and curable resin matrix. The composite may include a third layer 22 comprising fibre material orientated at a second angle to the reference, a toughening agent and curable resin matrix. A similar fourth layer, orientated at a third angle to the reference may be included. Multiple series of the four layers are disclosed with different pattern of layers and/or total number. The fibres are preferably unidirectional continuous fibres and preferably comprise carbon or glass fibres. The toughening agent is preferably a thermoplastic. Aircraft components comprising the composite are claimed. A method is also claimed comprising laying up a first layer of fibre with attached toughening agent, at a first angle, laying up a second layer on the first layer, the fibres arranged in the reference direction and then infusing the stack with a curable resin before applying heat and pressure to form a composite.

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A COMPOSITE MATERIAL

FIELD OF THE INVENTION [001] The present invention relates to composite materials and the use of composite material in structural components for aircraft. In particular the present invention relates to a composite material comprising toughened layer comprising dry fibre material and a method of manufacturing such a composite material.

BACKGROUND OF THE IN VENTION |002] Aircraft wings extend longitudinally from wing root to wing tip, approximately transverse to the direction of flight. During normal flight conditions, the upper wing skin of an aircraft is required to withstand compressive forces while the lower wing skin is required to withstand tensile forces in response to aerodynamic forces applied to the wings in flight. The stress arising from such forces tends to be transmitted longitudinally along the wing in both the skin and in structural components, such as stringers, in the longitudinal, or spanwise, direction along the length of the wing. Such components are commonly fabricated of composite materials.

[003| Advanced composite materials are typically characterised by high strength fibre reinforced matrices providing high stiffness and strength along the direction of the reinforcing fibre. Synthetic composite materials such as carbon fibre reinforced plastic (CFRP) commonly comprise a set of one or more layers of carbon fibre material infused with a resin to form a desired structure. The carbon fibres have an especially high modulus (the modulus of a material being the Young's modulus exhibited by the material when tensioned) and it becomes possible to provide a relatively thin and, consequently, relatively light wing skin of the required strength.

1004] It is commonly desired to provide openings in wing skins, on both a targe scale and a small scale, to allow access to the inside of the wing for inspection and maintenance purposes. Such openings are commonly referred to as manholes. The area of the wing skin or other composite component immediately adjacent the manhole can be subject to impact or other local stresses that may cause local structural damage. The area immediately adjacent a manhole is often subject to high stresses caused by weight and/or pressure exerted by the body of the person inspecting the wing interior during ground operations.

[005] A particular issue arises when a manhole is placed in a lower wing skin formed of a composite fibre and matrix material. A way of reducing the problem of localised damage to composite components is to thicken the composite material across the entire component, but this adds weight to the component and is likely to take away the potential weight advantage of using the composite material.

[006] it is therefore desirable to provide a composite material for an aircraft structural component that resists structural damage caused by high stresses and impact during ground operations without unduly weakening the ability of the component to withstand stress in flight.

SUMMARY OF INVENTION [007] According to a first aspect of the invention, there is provided a composite material comprising a first layer comprising a first composition of dry fibre material, a toughening agent and a matrix material; a second layer comprising a second composition of dry fibre material and the matrix material; wherein the fibres of the first dry fibre material are substantially oriented at a. first angle with respect to a longitudinal reference direction, the fibres of the second dry fibre material are substantially aligned with the longitudinal reference direction, and the matrix material comprises a curable resin.

[008] The composite material may further comprise a third layer comprising a third composition of dry fibre material, a toughening agent and the matrix material, wherein the fibres of the third dry fibre material may be substantially oriented at a second angle with respect to the longitudinal reference direction.

[009] The fibres of the first composition of dry fibre material may be arranged at an acute angle to a longitudinal reference direction and have a first modulus in respect of stress in the longitudinal reference direction. The toughening agent and matrix material of the first composition may provide a first tolerance of strain resulting from said stress.

I.010J The fibres of the second dry fibre material may be substantially aligned with the longitudinal reference direction and have a second modulus in respect of stress in the longitudinal reference direction that is greater than that of the first composition. The second composition may comprise a matrix providing a second tolerance of strain resulting from said stress that is smaller than that of the first layer.

[011| The fibres of the third composition of dry fibre material may be arranged at an angle normal to the longitudinal reference direction. The dry fibre material of the third composition may exhibit a modulus in respect of stress in the longitudinal reference direction that is substantially equal to that of the first composition, and the toughening agent and matrix exhibits a tolerance of strain resulting from such stress that is substantially equivalent to that of the first composition.

[012[ The composite material may comprise a plurality of layers, wherein the outermost layers of the plurality of layers may be comprised of the first or third compositions, and an intermediate layer may be comprised of the second composition.

i.013] The composite material may comprise a plurality of layers wherein the outermost layers of the plurality of layers may be comprised of the first or third compositions and a pair of innermost layers may comprise the first or third compositions, and at least one intermediate layer may be provided between the outermost layers and the pair of innermost layers, the intermediate layer comprising the second composition.

[014] The composite material may comprise an outermost layer of the plurality of layers comprised of the first composition, and a layer adjacent the outermost layer comprised of the third composition.

[015] The composite material may comprise a pair of innermost layers comprising the first and third compositions, and a plurality of intermediate layers may be provided between the layer adjacent the outermost layer and the pair of innermost layers comprising the second composition.

[016| The composite material may comprise 60% of the plurality of layers of the second composition and 40% of the plurality of layers may be of the first or third compositions.

1017] The composite material may comprise sixteen layers, in which a first, outermost layer of the plurality of layers is comprised of the first composition, a second layer adjacent the outermost layer may be comprised of the third composition, a third layer adjacent the second layer may be comprised of the second composition, a fourth layer adjacent the third layer may be comprised of the second composition, a fifth layer adjacent the fourth layer may be comprised of the second composition, a sixth layer adjacent the fifth layer may be comprised of the second composition, a seventh layer adjacent the sixth layer may be comprised of the second composition, an eighth, innermost layer adjacent the seventh layer may be comprised of the third composition, a ninth, innermost layer adjacent the eighth layer may be comprised of the first composition, a tenth layer adjacent the ninth layer may be comprised of the second composition, an eleventh layer adjacent the tenth layer may be comprised of the second composition, a twelfth layer adjacent the eleventh may be comprised of the second composition, a thirteenth layer adjacent the twelfth may be comprised of the second composition, a fourteenth layer adjacent the thirteenth layer may be comprised of the second composition, a fifteenth layer adjacent the thirteenth layer may be comprised of the third composition, and a sixteenth, outermost layer may be comprised of the first composition.

[018] The composite material may further comprise a fourth layer comprising a fourth composition of dry fibre material, a toughening agent and the matrix material, wherein the fibres of the fourth fry fibre material may be oriented substantially normal with respect to the longitudinal reference direction.

[019] The dry fibre material of the fourth composition may exhibit a modulus in respect of stress in the longitudinal reference direction that is lower than that of the second composition and greater than that of the first composition, and the toughening agent and matrix may exhibit a tolerance of strain resulting from such stress that is substantially equivalent to that of the first composition.

[020] The composite material may comprise a plurality of layers wherein the outermost layers of the plurality of layers may be comprised of the first or third compositions and the innermost layers of the plurality of layers may comprise the fourth composition, and at least one intermediate layer of the plurality of layers comprising the second composition may be provided between the outermost and innermost layers, and at least one intermediate layer of the plurality of layers comprising the first, third or fourth compositions may be provided between the outermost and innermost layers.

(021 j The composite material may comprise an outermost layer of the plurality of layers of the first composition, and a layer adjacent the outermost layer comprised of the third composition.

[022] The composite material may comprise a pair of innermost layers of the fourth composition.

[023] The composite material may comprise a first and a second intermediate layer comprising the second composition provided between the layer adjacent the outermost layer and the pair of innermost layers, and a plurality of further intermediate layers provided between the layer adjacent the outermost layer and the pair of innermost layers, said further intermediate layers comprising a first composition, a third composition and a fourth composition.

j 024J The composite material may have 25% of the plurality of layers may be comprised of the second composition, 50% of the plurality of layers may be comprised of the first or third compositions, and 25% of the plurality of layers may be comprised of the fourth composition.

}025] The composite material may comprise sixteen layers, in which a first, outermost layer of the plurality of layers may be comprised of the first composition, a second layer adjacent the outermost layer may be comprised of the third composition, a third layer adjacent the second layer may be comprised of the second composition, a fourth layer adjacent the third layer may be comprised of the fourth composition, a fifth layer adjacent the fourth layer may be comprised of the first composition, a sixth layer adjacent the fifth layer may be comprised of the third composition, a seventh layer adjacent the sixth layer may be comprised of the second composition, an eighth, innermost layer adjacent the seventh layer may be comprised of the fourth composition, a ninth, innermost layer adjacent the eighth layer may be comprised of the fourth composition, a tenth layer adjacent the ninth layer may be comprised of the second composition, an eleventh layer adjacent the tenth layer may be comprised of the third composition, a twelfth layer adjacent the eleventh may be comprised of the first composition, a thirteenth layer adjacent the twelfth may be comprised of the fourth composition, a fourteenth 5 layer adjacent the thirteenth layer may be comprised of the second composition, a fifteenth layer adjacent the thirteenth layer may be comprised of the third composition, and a sixteenth, outermost layer may be comprised of the first composition.

[026[ The composite material may comprise a plurality of layers wherein the outermost layers of the plurality of layers may be comprised of the first or third compositions, and the innermost layers of the plurality of layers may be comprised of the first or third composition, at least one intermediate layer of the plurality of layers may comprise the second composition provided between the outermost and innermost layers, and at least one intermediate layer of the plurality of layers comprising the fourth composition may be provided between the outermost and innermost layers.

1027] The composite may comprise a first outermost layer of the plurality of layers comprised of the first composition, and a layer adjacent the outermost layer comprised of the third composition.

[028[ The composite material may comprise a pair of innermost layers comprised of the first and third compositions.

[029] The composite material may comprise a first and a second intermediate layer comprising the fourth composition provided between the layer adjacent the outermost layer and the pair of innermost layers, and a plurality of further intermediate layers comprising the second composition provided between the layer adjacent the outermost layer and the pair of innermost layers.

[030j The composite material may comprise 50% of the plurality of layers of the second composition, 40% of the plurality of layers of the first or third compositions, and 10% of the plurality of layers of the fourth composition.

[031 j The composite material may comprise sixteen layers, in which a first, outermost layer of the plurality of layers may be comprised of the first composition, a second layer adjacent the outermost layer may be comprised of the third composition, a third layer adjacent the second layer may be comprised of the second composition, a fourth layer adjacent the third layer may be comprised of the second composition, a fifth layer adjacent the fourth layer may be comprised of the second composition, a sixth layer adjacent the fifth layer may be comprised of the fourth composition, a seventh layer adjacent the sixth layer may be comprised of the second composition, an eighth, innermost layer adjacent the seventh layer may be comprised of the third composition, a ninth, innermost layer adjacent the eighth layer may be comprised of the first composition, a tenth layer adjacent the ninth layer may be comprised of the second composition, an eleventh layer adjacent the tenth layer may be comprised of the fourth composition, a twelfth layer adjacent the eleventh may be comprised of the second composition, a thirteenth layer adjacent the twelfth may be comprised of the second composition, a fourteenth layer adjacent the thirteenth layer may be comprised of the second composition, a fifteenth layer adjacent the thirteenth layer may be comprised of the third composition, and a sixteenth, outermost layer maybe comprised of the first composition.

[032] The composite material may comprise fibres of the first composition of dry fibre material that are substantially oriented at 135° with respect to the longitudinal reference direction.

j033] The composite material may comprise fibres of the second composition of dry fibre material that are substantially oriented at 0° with respect to the longitudinal reference direction.

]034] The composite material may comprise fibres of the third composition of dry fibre material that are substantially oriented at 45° with respect to the longitudinal reference direction.

j'035] The composite material may comprise fibres of the fourth composition of dry fibre material that are substantially oriented at 90° with respect to the longitudinal reference direction.

[036) The composite material may comprise fibres of the first, second, third, or fourth dry fibre material that are uni-directional continuous fibre.

[037] The composite material may comprise fibres of the first, second, third, or fourth dry fibre material of carbon fibre.

[038] The composite material may comprise fibres of the first, second, third, or fourth dry fibre material that are glass fibre.

j 039] The composite material may comprise a curable resin that is any one of epoxy resin, polyester resin, phenolic resin, vinyl ester resin or bismaleimide (BMi) resin.

!<M0j The composite material may comprise a toughening agent comprising a thermoplastic.

[041 j According to a second aspect, there is provided a structural component for an aircraft comprising the composite material.

[042] The structural component may be an aircraft skin.

[043] The structural component may be an aircraft skin comprising one or more apertures.

[044] According to a third aspect, there is provided a method of forming a composite material, the method comprising the steps of providing a first layer on a tool face, the first layer comprising a dry fibre material having fibres arranged at a first angle with respect to a longitudinal reference direction and a toughening agent attached to the dry fibre material, providing a second layer on the first layer, the second layer comprising a dry fibre material having fibres arranged in alignment with the longitudinal reference direction, infusing the assembled stack with a curable resin, and curing the assembled composite material by applying pressure and heat at a temperature sufficient to form a unitary composite material.

[045] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects. For example, the method of the present invention may incorporate any of the features described with reference to the apparatus of the present invention and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS ]046] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which:

[047] Figure 1 is a schematic view of an exemplary aircraft, [048] Figure 2 is a schematic view of an aircraft component comprising a section of wing forming a manhole plank, [049] Figure 3 is a schematic diagram of a composite material according to a first embodiment, [050] Figure 4 is a schematic diagram of a composite material according to a second embodiment, [051] Figure 5 is a schematic diagram of a composite material according to a third embodiment, [052] Figure 6 is a schematic diagram of a composite material according to a fourth embodiment, and [053] Figure 7 is a block diagram indicating a method of forming the composite material of the first, second, third or fourth embodiments.

DETAILED DESCRIPTION OF THF. INVENTION [054] Referring to Figure 1, there is shown a schematic view of an exemplary aircraft 2 having an aircraft wing 4 comprising a skin of composite material. The internal wing structure comprises a combination of spars, ribs, and stringers, any or all of which may be fabricated from composite materials. The longitudinal direction of the composite material fibre reinforcement is typically aligned from wing root 6 to wing tip 8 in a spanwise direction to provide maximum strength, and thus optimal load carrying properties, in said direction. Divers of composite material that have a general longitudinal direction aligned with the wing root 6 to wing tip 8 direction are referred to as having a 0° orientation.

[055] The longitudinal direction of the fibres within a composite material defines what is known as the fibre orientation. Fibre orientation herein is described according to the Laminate Orientation Code used in advanced composites design and with which the skilled person will be familiar. The angle value represents the degree of deviation from the 0° angle, which is the primary load carrying direction of the fibres in use. The 0° angle is ordinarily parallel to the longitudinal direction of the structure, herein referred to as the longitudinal reference direction.

In layers having an orientation of 90°, the longitudinal direction of the fibres is perpendicular or normal to those of the 0° orientation. As can be seen in Figure 1, the longitudinal reference direction is aligned with the wing root 6 to wing tip 8 direction.

[056] Embodiments of the invention may be directed toward the skin of an aircraft wing 4 of composite material. Manholes are typically provided in a wing skm via a section comprising one or more manholes, known as a manhole plank. Figure 2 shows a manhole plank 10 having three manholes 12. The manhole plank 10 is shown as flat but it will be appreciated that it may incorporate an aerodynamic or other such profile appropriate to its specific application.

[057] The manhole plank 10 is comprised of composite material having 0° fibres oriented the length of the plank such that fibres laid up in 0° orientation are aligned with the longitudinal axis 14 of manhole plank 10. The longitudinal 0° fibres of the manhole plank 10 are continuous except where interrupted by manholes 12. When the manhole plank 10 is assembled to form an aircraft skin, the longitudinal axis 14 of the manhole plank 10 is aligned from wing root 6 to wing tip 8 of an aircraft wing 4 as indicated in Figure 1.

[058] Figure 3 shows a composite material 16 according to a first embodiment for use in the manhole plank 10 of Figure 2. The composite material 16 is comprised of two outermost layers 18, 22 of a first composition and an innermost layer 20 of a second composition.

[059j The first layer 18 is of a first composition that comprises a dry fibre material arranged at an acute angle of 135° to the longitudinal reference direction and a toughening agent in the form of thermoplastic veils in an epoxy resin matrix. The toughening agent interacts with the matrix to produce a layer that is more ductile as compared to a layer in which the toughening agent is not present. This brings about the advantage of increased damage tolerance properties in the first layer 18 as compared to layers absent a toughening agent. The resulting matrix material can withstand a higher internal strain before fracture and delamination occurs as compared to untoughened layers.

[060] The second layer 20 is of a second composition that comprises a dry fibre material arranged in a 0° orientation in an epoxy resin matrix. The fibre orientation at 0° provides the advantage of a composite layer having an increased modulus and therefore enhanced 10 performance in tension as compared to layers having fibre material oriented at an angle from the longitudinal reference direction. The absence of the toughening layer helps distribute the load from individual fibres across the thickness of the material and in a planar manner as well as providing a cost benefit.

[061 j The third layer 22 is identical to the first 18 in that it is comprised of the first composition having a dry fibre material arranged in a 135° orientation and a toughening agent in an epoxy resin matrix. The second layer 20 is disposed between the first 18 and third 22 layers such that the first 18 and third 22 layers provide protection to the second 20 load carrying layer, the second layer 20 being prone to fatigue failure caused by damage in use affected by scratches, for example.

[062[ In each of the three layers 18, 20, 22, the dry fibre reinforcement material is a unidirectional continuous fibre in which the fibres of each layer run in a single direction. The continuous fibre provides a continuous load path in the longitudinal direction of the fibres.

[063] The composite material of the embodiments defined herein are particularly suitable for use in components having apertures or protrusions. The fibres of the outer layers are oriented at an acute angle to provide protection to the load carrying 0° fibre layers. Advantageously, there is a smaller step change between orientations to efficiently transmit load from one layer or ply to an adjacent layer to distribute tensile, compressive or other forces throughout the layers to relieve areas of stress concentration.

[064j A schematic of a composite material 24 of the second embodiment is shown in Figure 4. The overall percentage split of the composite material 24 in respect of fibre material orientation is that 25% of the layers have fibres that are load carrying and oriented at 0°, 50% of the layers have fibres oriented at an acute angle to the longitudinal reference direction, and 25% of the layers have fibres that are oriented normal to the longitudinal reference direction. As such, 25% of the layers are absent a toughening agent. The combination of orientations of each respective layer is selected according to the mechanical properties required of the composite material in use [065] The lay-up of the second embodiment, as indicated in Figure 4, is quasi-isotropic such that the isotropic properties of the composite material 24 are oriented in the 0° direction although the material is not restricted to isotropic out-of-plane responses.

[066] A summary of the structure of Figure 4 is shown in the following table:

Layer No.	Layer Ref. No.	Fibre Orientation	M ate rid
16	56	135°	Toughened UD Dsy Fibre
15	54	45°	Toughened UD Dry Fibre
14	52	0°	Untoughened UD Dry Fibre
13	50	90°	Toughened UD Dry Fibre
12	48	135°	Toughened UD Dry Fibre
11	46	45°	Toughened UD Diy Fibre
10	44	0°	Untoughened UD Dry Fibre
9	42	90°	Toughened UD Dry Fibre
8	40	90°	Toughened UD Dry Fibre
'Ί	38	0°	Untoughened UD Drv Fibre
6	36	45°	Toughened UD Diy Fibre
5	34	135°	Toughened UD Dry Fibre
4	32	90°	Toughened UD Dry Fibre
n 3	30	0°	Untoughened UD Dry Fibre
3 2.-	28	45°	Toughened UD Dry Fibre
1	26	135°	Toughened UD Dry Fibre	TOOL FACE

Table 1: Summary of structure of the composite material according to the second embodiment j067j Referring to Figure 4, the composite material 24 is formed of sixteen layers, the first layer 26, designated layer 1 in the above table, is laid upon the tool face during material manufacture, in all of the embodiments described herein, the layers are numbered from one face of the composite material to the other, and, where the composite material is formed into a component, from one face of the component to the other. The first 26 and sixteenth 56 are the outermost layers whilst the eighth 40 and ninth 42 layers are the innermost layers that straddle the mid-plane 54 of the composite material.

[068] A first layer 26 is of a first composition in which the fibres are arranged in a 135° orientation. Said layer comprises a toughening agent in the form of a thermoplastic veil in the 12 epoxy matrix material. A second layer 28 of a third composition is arranged adjacent the first layer 26. The second layer 28 also comprises a toughening agent, and has fibre material at an acute angle to the longitudinal reference direction at 45°. The fibres of the first 26 and second 28 layers are oriented at an acute angle to carry shear forces in the direction of orientation of the fibres. Advantageously, the arrangement of a layer having fibres angled at 45° to the reference direction next to a layer having fibres angled at 135° to the reference direction provides a symmetry in shear force resistance that prevents twisting and asymmetry in the composite material.

|069] The provision of two adjacent layers both having fibres at an acute angle to the longitudinal reference direction provides a smaller step change between orientations to efficiently transmit load from one layer to an adjacent layer to distribute forces throughout the layers to relieve areas of stress concentration. Further, the first 26 and second 28 layers of the second embodiment have a toughened matrix arranged to provide a region having improved damage tolerance properties as compared to a layer in which the toughening agent is absent.

[070] The third layer 30 is of a second composition in which the fibres are arranged in a 0° orientation in an epoxy resin matrix. The absence of a thermoplastic toughening agent in the third layer 30 allows the resin to support the fibres and provide increased compressive strength that in turn provides the advantage of increased resistance to fibre buckling under load.

[071] Advantageously, the juxtaposition of layers having a toughening agent and layers in which the toughening agent is absent provides a composite material with enhanced damage tolerance capability whilst mitigating the disadvantageous mechanical properties associated with each layer type.

[072] The fourth layer is of a fourth composition comprising a dry fibre material arranged at an angle of 90° to the longitudinal reference direction and a toughening agent in the form of thermoplastic veils in an epoxy resin matrix.

[073] The fibre material of the fourth 32, fifth 34 and sixth 36 layers of the composite material are oriented at 90°, 135° and 45° respectively, each of said layers comprising a toughening agent.

The smaller difference in fibre orientation angle between adjacent layers allows for easier load transmission and dissipation of stress between said layers.

[074] The seventh layer 38 of the composite material is positioned to provide a further load carrying layer and as such the fibre material is oriented at 0° in an untoughened matrix material.

j075j The eighth 40 and ninth 42 layers of the composite material, between which lies the mid plane 58 of the stack, are comprised of toughened layers oriented at 90°. Advantageously, the lay-up is symmetrical such that the ninth 42, tenth 44, eleventh 46, twelfth 48, thirteenth 50, fourteenth 52, fifteenth 54 and sixteen 56 layers above the mid-plane 58, or centre line, of the composite material mirror layers one 26 to eight 40 below the mid-plane such that the fibres of the ninth 42 to sixteenth 56 layers represent a mirror image of the first 26 to eighth 40 layers in both ply orientation and material type. Advantageously, a symmetrical lay-up prevents material warping during the manufacture process and provides increased structural stability in the resulting material.

(076j A schematic of the composite material 60 of the second embodiment is shown in Figure 5, in which fibre orientation and material type is selected to provide a medium composite that is neither predominantly hard nor soft. The percentage of layers having fibre material orientated at 0° to the longitudinal reference direction is 50%, 40% of layers have fibre material oriented at an acute angle to the longitudinal reference direction, and 10% of layers have fibre material oriented normal to the longitudinal reference direction. In the third embodiment, 50% of layers have a fibre material oriented at 0° in an untoughened layer.

[077] The structure of the composite material 60 of the second embodiment is summarized in the following table:

Layer No.	Layer Ref. No.	Fibre Orientation	M ate rial
16	92	135°	Toughened UD Dry Fibre
15	90	45°	Toughened UD Dry⁷ Fibre
14	88	0°	Untoughened UD Dry Fibre
13	86	0°	Untoughened UD Dry Fibre
12	84	0°	Untoughened UD Dry Fibre
11	82	90°	Toughened UD Dry Fibre
10	80	0°	Untoughened UD Dry⁷ Fibre
9	78	135°	Toughened UD Dry⁷ Fibre
8	76	45°	Toughened UD Dry Fibre
7	74	0°	Untoughened UD Dry Fibre
6	72	90°	Toughened UD Dry Fibre
5	70	0°	Untoughened UD Dry Fibre
4	68	0°	Untoughened UD Dry⁷ Fibre
3	66	0°	Untoughened UD Dry⁷ Fibre
2	64	45°	Toughened UD Dry⁷ Fibre
1	62	135°	Toughened UD Dry Fibre	TOOL FACE

'Fable 2 : Summary of structure of the composite material according to the third embodiment [078j Referring to Figure 5, the first 62 and second 64 layers of the third embodiment, designated layers 1 and 2 in Table 2, are comprised of a first and third composition respectively, having fibre material arranged at an acute angle to the longitudinal reference direction at 135° and 45° respectively. Both the first layer 62 and the second layer 64 comprise a thermoplastic toughening agent in an epoxy resin matrix.

[079] The fibres of the third 66, fourth 68, and fifth 70 layers are of a second composition in which fibres are oriented at 0°. .Advantageously, the direction of the fibres of each of said layers is locally parallel and provides longitudinal load carrying properties. The matrix material in said layers is epoxy resin. The provision of three adjacent layers of load bearing fibres provides the advantage of a substantial region within the composite material for carrying shear loads in the longitudinal direction of the fibres. The arrangement of the first 62 and second 64 toughened layers at the outer surface of the material in respect of the adjacent 0° load carrying layers provides a degree of impact and/or scratch resistance to said 0°load carrying layers.

[080] The sixth layer 72 of the third embodiment is of a fourth composition in which the fibres are oriented at 90° to the longitudinal reference direction, with a toughening agent in an epoxy resin matrix to provide resistance to bending or loading in a lateral direction. The seventh layer 74 is a further load carrying layer having fibres oriented at 0° in a curable resin matrix.

[081] The eighth 76 and ninth 78 layers are comprised of fibre material oriented at 45° and 135° respectively with a toughening agent in an epoxy resin matrix arranged around the midplane 94 of the composite material. The lay-up is therefore not fully symmetrical with respect to fibre orientation. Advantageously, the asymmetry is located across the mid-plane 94 to minimise any warping or buckling effect in the composite material. However, the first 62 to seventh 74 layers of the composite material are symmetrical with respect to the tenth 80 to sixteenth 92 layers in both ply orientation and material type and are arranged in reverse order accordingly.

[082] The tenth 80, eleventh 82, twelfth 84, thirteenth 86, fourteenth 88, fifteenth 90, and sixteenth 92 layers represent a mirror image of the first 62 to seventh 74 layers. Although the fibre orientation of the layers of this embodiment are not fully symmetrical in respect of fibre orientation, the distribution of layers having a toughening agent is symmetrical across the midplane 94, [083] A composite material 96 of a fourth embodiment is shown in Figure 6, in which a selectively toughened hard lay-up in which 60% of fibre reinforcement layers are aligned with the longitudinal reference direction for load carrying properties and 40% of layers have fibre material laid in the 45° and 135° orientations. Accordingly, 60% of the layers of the exemplary embodiment are absent a toughening agent.

[084] A summary of the composite material 96 of the fourth embodiment is shown in the following table:

Layer No.	Laye r Ref. No.	Fibre Orientation	Material
16	128	135°	Toughened UD Dry Fibre
15	126	45°	Toughened UD Dry Fibre
14	124	0°	Untoughened UD Dry Fibre
13	122	0°	Untoughened UD Dry Fibre
12	120	0°	Untoughened UD Diy Fibre
11	118	0°	Untoughened UD Dry Fibre
10	116	0°	Untoughened UD Dry Fibre
9	114	135°	Toughened UD Dry Fibre
8	112	45°	Toughened UD Dry Fibre
7	110	0°	Untoughened UD Dry Fibre
6	108	0°	Untoughened UD Dry Fibre
5	106	0°	Untoughened UD Dry Fibre
4	104	0°	Untoughened UD Dry Fibre
J	102	0°	Untoughened UD Diy Fibre
2	100	45°	Toughened UD Dry Fibre
1	98	135°	Toughened UD Dry Fibre	FOOL FACE

Table 3: Summary of structure of the composite material according to the fourth embodiment [085] Referring to Figure 6, the first 98 layer, designated layer 1 in Table .3, is of a first composition comprising a dry fibre material arranged at an acute angle of 135° to the longitudinal reference direction and a toughening agent in the form of thermoplastic veils in an epoxy resm matrix.

[086] The second 100 layer of the fourth embodiment is of a third composition comprising a fibre material oriented at 45° and a toughening agent in an epoxy resin matrix.

[087] The third 102, fourth 104, fifth 106, sixth 108, and seventh 110 layers of the composite material 96 are comprised of a second composition in which fibre material is oriented at 0° in a resm matrix. The selection of five adjacent layers of fibre material laid in the 0° orientation is considered unconventional and provides a significant region of stiffness with respect to compressive properties and is particularly desirable in applications in which the material is subject to minimal loading or bending in a lateral direction.

[088] This may be particularly advantageous in applications in which it is preferable for the composite material to fail in the direction of the 0° fibres. In contrast to damage caused by impact to composite materials having few layers of 0° oriented fibres, or layers of 0°oriented fibres interspaced with layers having fibres at other orientations, damage caused by significant stress resulting from impact propagates in the direction of the 0° fibres in a linear fashion through the untoughened layers. It is therefore possible to influence the failure mode of the composite material by providing selectively toughened layers such that damage is directed away from critical components or critical areas of components in which failure is least desirable.

[089] The eighth 112 and ninth 114 layers are comprised of fibre material arranged at 45° and 135° respectively, with a toughening material in an epoxy resin matrix around the mid-plane 130 of the composite material. The layers of the composite material 96 are not fully symmetrical in respect of fibre orientation. However, the layers of the fourth embodiment are symmetrically arranged around the mid-plane 130 of the composite material 96 in respect of layers having a toughening agent and those in which a toughening agent is not present. The tenth 116, eleventh 118, twelfth 120, thirteenth 122, fourteenth 124, fifteenth 126, and sixteenth 128 layers represent a mirror image of the first 98 to seventh 110 layers in both ply orientation and material type and are arranged in reverse order accordingly.

[090] The composite material .16, 24, 60, 96 of the embodiments defined herein are particularly suitable for use in components having apertures or protrusions, such as the manhole plank 10 of figure 2. The fibres of the outer layers are oriented at an acute angle to provide protection to the load carrying 0° fibre layers. Advantageously, there is a smaller step change between orientations to efficiently transmit load from one layer or ply to an adjacent layer to distribute tensile, compressive or other forces throughout the layers to relieve' areas of stress concentration.

[091] Figure 7 is a block diagram indicating a method of manufacturing the composite material 16, 24, 60, 96 of any one of the embodiments disclosed herein. The method comprises the step 132 of laying up the layers of composite material, the step 134 of resin infusion and the step 136 of curing. In step 132 of the exemplary method of forming a composite material, a first layer of dry fibre material is assembled on a tool face. The fibres of each layer are laid down by hand on a lay-up table or on a tool using known automated methods, the first and last layers forming the outermost layers of the cured composite material. Thermoplastic veils are attached to the layer of dry fibre material as a toughening agent.

(092] In step 134, subsequent to the lay-up of the layers into a stack, a curable resin is applied to the stack by known infusion methods. Suitable methods include vacuum injection, in w'hich curable resin is homogeneously distributed through the stack by means of a vacuum system. The skilled person will appreciate that other known manufacturing methods, such as liquid resin infusion, may be selected.

1093) In step 136, heat is applied to the resin infused stack. The temperature is sufficient for the toughening agent to react with the resin to form a unitary composite material. The thermoplastic toughening agent remains solid throughout the manufacturing process and thereafter. Other types of toughening agent may be selected that provide a consistent and homogeneous toughening across the whole of the layer in which the toughening agent is present. Advantageously, during the manufacturing process, the toughening agent prevents the epoxy matrix material from cracking thus changing the modulus of the layer such that the cured layer is a more ductile layer with increased resistance to delamination.

1094] Curing can take place at atmospheric pressure thus negating the need for a pressure chamber. However, in certain instances, use of a pressure chamber may be advantageous, particularly where the composite material is formed into complex shapes. Curing may take place at a high pressure or a low pressure. The cure may be a high or low temperature cure.

[095] The step of laying up 132 may comprise laying up the layers according to any of the first, second third or fourth embodiments. By w'ay of example, the step of laying up the layers according to the third embodiment, as described in Figure 5, wall now' be described.

[096] The dry fibre material of the first layer 62 is laid onto a tool face at a 135° orientation to the longitudinal reference direction. Thermoplastic veils are attached to the layer of dry fibre material as a toughening agent. The dry fibre material of the second layer 64 is laid upon those of 19 the first layer 62 at 45° to the longitudinal reference direction. Thermoplastic veils are attached the fibre material of the second layer 64 as a toughening agent.

[097] Dry fibre material of the third layer 66 is laid upon the second layer 64 such that the fibres of the dry fibre material are oriented in alignment with the longitudinal reference direction at a 0° orientation. The dry fibre material of the fourth layer 68 is laid upon the fibres of the third layer 66 at a 0° orientation to the longitudinal reference direction. The dry fibres of the fifth layer 70 are laid upon the fourth layer 68 such that the fibres of the dry fibre material are oriented in alignment with the longitudinal reference direction at a 0° orientation.

j 098j The sixth layer 72 of dry fibre material is laid upon the fifth layer 70, the sixth layer 72 having fibres arranged at 90° to the longitudinal reference direction with a toughening agent attached to the dry fibre material. The seventh layer 74 is laid upon the fibres of the sixth layer 72 at a 0° orientation to the longitudinal reference direction.

[099] The dry fibre material of the eighth layer 76 is laid upon those of the seventh layer 74 at 45° to the longitudinal reference direction. Thermoplastic veils are attached the fibre material of the eighth layer 76 as a toughening agent. The dry fibre material of the ninth layer 78 is laid upon those of the eighth layer 76 at 135° to the longitudinal reference direction. Thermoplastic veils are attached the fibre material of the ninth layer 78 as a toughening agent.

[0100] Dry fibre material of the tenth layer 80 is laid upon the ninth layer 78 such that the fibres of the dry fibre material are oriented in alignment with the longitudinal reference direction at a 0° orientation. The eleventh layer 82 of dry fibre material is laid upon the tenth layer 80, the eleventh layer 82 having fibres arranged at 90° to the longitudinal reference direction with a toughening agent attached to the dry fibre material.

j0101 j Dry fibre material of the twelfth layer 84 is laid upon the eleventh layer 82 such that the fibres of the dry fibre material are oriented in alignment with the longitudinal reference direction at a 0° orientation. The dry fibre material of the thirteenth layer 86 is laid upon the fibres of the twelfth layer 84 at a 0° orientation to the longitudinal reference direction. The dry fibres of the fourteenth layer 88 are laid upon the thirteenth layer 86 such that the fibres of the dry fibre material are oriented in alignment with the longitudinal reference direction at a 0° orientation.

[ΟΙ 02] The dry fibre material of the fifteenth layer 90 is laid upon those of the fourteenth layer 88 at 45° to the longitudinal reference direction. Thermoplastic veils are attached the fibre material of the fifteenth layer 90 as a toughening agent. The dry fibre material of the sixteenth layer 92 is laid onto the fifteenth layer 90 at a 135° orientation to the longitudinal reference direction. Thermoplastic veils are attached to the layer of dry fibre material as a toughening agent.

[0103] In further embodiments, the layers are laid up according to the layer arrangements described in Figures 3, 4 or 6.

[0104] In a subsequent step 134, a curable resin is applied to the layers by a known infusion method. The resin is applied to the layers such that it is fully distributed throughout and across each of the layers. A vacuum may be applied to the resin infused layers to both aid in the distribution of resin and to hold the layers in position, as desired.

[0105] The resin infused assembled layers are cured in a further step 136 by applying heat in any suitable known manner. The curing temperature will be selected according to the fibre and resin materials used.

[0106] Although in the exemplary embodiments the composite material is comprised of sixteen layers, it should be appreciated that the composite material may be comprised of any number of layers selected to provide desirable mechanical properties in the manufactured material or component.

[0107] The fibre material may be a may be uni-directional continuous fibre such as carbon fibre or any other suitable material, including glass fibre.

[0108] The curable resin is not restricted to epoxy resin. The curable resin may be any one of epoxy resin, polyester resin, phenolic resin, vinyl ester resin or bismaleimide (BMI) resin. Other resin types that are naturally tough may be provided as an alternative to the presence of the toughening agent in layers in which a toughening is desirable if the naturally tough matrix material is compatible with the matrix material chosen for the untoughened layer.

[0109] The toughening agent is not restricted to thermoplastic veils and may be comprised of any suitable additive in a suitable format, including sheet and particles.

jOllO] Where the composite material of the exemplary embodiments is laid up to form a manhole plank 10 as per Figure 2, or other structural component, the component may be laid up at the same time as the composite material of the remainder of the wing surface is laid up such that the entire wing surface may be cured as a unitary composite structure. Alternatively, the composite material of the exemplary embodiments may be laid up to form the manhole plank 10 or component and cured as a discrete part prior to assembly into a complex part.

[0111] Alternatively, the wing skin may be comprised of the exemplary composite material in its entirety. The skin of other parts of an aircraft, for example the fuselage or horizontal tailpiane, may be comprised of the exemplary composite material.

[0112] In a further preferred embodiment, the composite material of the exemplary embodiments is applied to structures and components having apertures of any size, including bolt holes and apertures formed to accommodate windows and doors.

[0113] In the exemplary embodiments disclosed herein, the composite material may be provided in a group comprising more than one layers of fibres known as a blanket of composite material.

[0114] A blanket of composite material is typically formed of twO, three or four layers of composite fibres. Each blanket of fibres may comprise layers of fibres laid in a bi-axial, tri-axial and quad-axial arrangement respectively. Each blanket may be formed of layers of dry fibre material in selected orientations that are subsequently assembled to form the requisite number of layers and combination of orientations as per the exemplary embodiments described. Blankets may be laid up to form the composite material of any one of embodiments one to four prior to resin infusion and curing. Assembly of two or more dry fibre layers into blankets prior to lay-up provides a significant time saving that allows for increased rate of manufacture without compromising material quality or integrity. This represents a significant advantage over composite lay-ups comprised of pre-impregnated composite fibres laid up layer by layer.

[0115j it should be noted that embodiments of the present application may be directed towards applications for technologies outside the aerospace industry (e.g., automotive, etc.). Furthermore, the exemplar,' composite material can be directed to any suitable structure.

[0116] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.

Claims

1. A composite material comprising;

a first layer comprising a first composition of dry fibre material, a toughening agent and a matrix material;

a second layer comprising a second composition of dry fibre material and the matrix material;

wherein the fibres of the first dry fibre material are substantially oriented at a first angle with respect to a longitudinal reference direction, the fibres of the second dry fibre material are substantially aligned with the longitudinal reference direction, and the matrix material comprises a curable resin.

2. A composite material according to claim 1, further comprising;

a third layer comprising a third composition of dry fibre material, a toughening agent and the matrix material, wherein the fibres of the third dry fibre material are substantially oriented at a second angle with respect to the longitudinal reference direction.

3. A composite material according to claim 2, comprising a plurality of layers, wherein the outermost layers of the plurality of Sayers are comprised of the first or third compositions, and an intermediate layer is comprised of the second composition.

4. A composite material according to claim 2, comprising a plurality of layers wherein the outermost layers of the plurality of layers are comprised of the first or third compositions and a pair of innermost layers comprise the first or third compositions, and at least one intermediate layer is provided between the outermost layers and the pair of innermost layers, the intermediate layer comprising the second composition.

5. A composite material according to claim 3 or claim 4, wherein an outermost layer of the plurality of layers is comprised of the first composition, and a layer adjacent the outermost layer is comprised of the third composition.

6. A composite material according to claim 5, wherein a pair of innermost layers comprise the first and third compositions, and a plurality of intermediate layers provided between the layer adjacent the outermost layer and the pair of innermost layers comprise the second composition.

7. A composite material according to claim 5 or claim 6, wherein 60% of the plurality of layers comprises the second composition and 40% of the plurality of layers comprises the first or third compositions.

8. .A composite material according to any one of claims 4 to 7, wherein the composite material comprises 16 layers, in which a first, outermost layer of the plurality of layers is comprised of the first composition, a second layer adjacent the outermost layer is comprised of the third composition, a third layer adjacent the second layer is comprised of the second composition, a fourth layer adjacent the third layer is comprised of the second composition, a fifth layer adjacent the fourth layer is comprised of the second composition, a sixth layer adjacent the fifth layer is comprised of the second composition, a seventh layer adjacent the sixth layer is comprised of the second composition, an eighth layer adjacent the seventh layer is comprised of the third composition, a ninth layer adjacent the eighth layer is comprised of the first composition, a tenth layer adjacent the ninth layer is comprised of the second composition, an eleventh layer adjacent the tenth layer is comprised of the second composition, a twelfth layer adjacent the eleventh is comprised of the second composition, a thirteenth layer adjacent the twelfth is comprised of the second composition, a fourteenth layer adjacent the thirteenth layer is comprised of the second composition, a fifteenth layer adjacent the thirteenth layer is comprised of the third composition, and a sixteenth, outermost layer is comprised of the first composition.

9. A composite material according to claim 1 or claim 2, further comprising;

a fourth layer comprising a fourth composition of dry fibre material, a toughening agent and the matrix material, wherein the fibres of the fourth fry fibre material are oriented substantially normal with respect to the longitudinal reference direction.

10. A composite material according to claim 9, comprising a plurality of layers wherein the outermost layers of the plurality of layers are comprised of the first or third compositions and the innermost layers of the plurality of layers comprise the fourth composition, and at least one intermediate layer of the plurality of layers comprising the second composition is provided between the outermost and innermost layers, and at least one intermediate layer of the plurality of layers comprising the first, third or fourth compositions is provided between the outermost and innermost layers.

11. A composite material according to claim 9 or claim 10, wherein an outermost layer of the plurality of layers is comprised of the first composition, and a layer adjacent the outermost layer is comprised of the third composition.

1.2. A composite material according to claim 11, wherein a pair of innermost layers is comprised of the fourth composition.

13. A composite material according to claim 12, wherein a first and a second intermediate layer comprising the second composition are provided between the layer adjacent the outermost layer and the pair of innermost layers, and a plurality of further intermediate layers is provided between the layer adjacent the outermost layer and the pair od innermost layers, said further intermediate layers comprising a first composition, a third composition and a fourth composition.

14. A composite material according to any one of claims 9 to 13, wherein 25% of the plurality of layers comprises the second composition, 50% of the plurality of Sayers comprises the first or third compositions, and 25% of the plurality of Sayers comprises the fourth composition.

15. A composite material according to any one of claims 9 to 14, wherein the composite material comprises 16 layers, in which a first, outermost layer of the plurality of layers is comprised of the first composition, a second layer adjacent the outermost layer is comprised of the third composition, a third layer adjacent the second layer is comprised of the second composition, a fourth layer adjacent the third layer is comprised of the fourth composition, a fifth layer adjacent the fourth layer is comprised of the first composition, a sixth layer adjacent the fifth layer is comprised of the third composition, a seventh layer adjacent the sixth layer is comprised of the second composition, an eighth layer adjacent the seventh layer is comprised of the fourth composition, a ninth layer adjacent the eighth layer is comprised of the fourth composition, a tenth layer adjacent the ninth layer is comprised of the second composition, an eleventh layer adjacent the tenth layer is comprised of the third composition, a twelfth layer adjacent the eleventh is comprised of the first composition, a thirteenth layer adjacent the twelfth is comprised of the fourth composition, a fourteenth layer adjacent the thirteenth layer is comprised of the second composition, a fifteenth layer adjacent the thirteenth layer is comprised of the third composition, and a sixteenth, outermost layer is comprised of the first composition.

16. A composite material according to claim 9, comprising a plurality of layers wherein the outermost layers of the plurality of Sayers are comprised of the first or third compositions and the innermost layers of the plurality of layers are comprised of the first or third composition, at least one intermediate layer of the plurality of layers comprising the second composition is provided between the outermost and innermost layers, and at least one intermediate layer of the plurality of layers comprising the fourth composition is provided between the outermost and innermost layers.

17. A composite material according to claim 16, wherein a first outermost layer of the plurality of layers is comprised of the first composition, and a layer adjacent the outermost layer is comprised of the third composition.

18. A composite material according to claim 17, wherein a pair of innermost layers are comprised of the first and third compositions.

19. A composite material according to claim 18, wherein a first and a second intermediate layer comprising the fourth composition are provided between the layer adjacent the outermost layer and the pair of innermost layers, and a plurality of further intermediate layers comprising the second composition are provided between the layer adjacent the outermost layer and the pair of innermost layers

20. composite material according to any one of claims 16 to 19, wherein 50% of the plurality of layers comprises the second composition, 40% of the plurality of layers comprises the first or third compositions, and 10% of the plurality of layers comprises the fourth composition.

21. A composite material according to any one of claims 16 to 20, wherein the composite material comprises 16 layers, in which a first, outermost layer of the plurality of layers is comprised of the first composition, a second layer adjacent the outermost layer is comprised of the third composition, a third layer adjacent the second layer is comprised of the second composition, a fourth layer adjacent the third layer is comprised of the second composition, a fifth layer adjacent the fourth layer is comprised of the second composition, a sixth layer ad jacent the fifth layer is comprised of the fourth composition, a seventh layer adjacent the sixth layer is comprised of the second composition, an eighth layer adjacent the seventh layer is comprised of the third composition, a ninth layer adjacent the eighth layer is comprised of the first composition, a tenth layer adjacent the ninth layer is comprised of the second composition, an eleventh layer adjacent the tenth layer is comprised of the fourth composition, a twelfth layer adjacent the eleventh is comprised of the second composition, a thirteenth layer adjacent the twelfth is comprised of the second composition, a fourteenth layer adjacent the thirteenth layer is comprised of the second composition, a fifteenth layer adjacent the thirteenth layer is comprised of the third composition, and a sixteenth, outermost layer is comprised of the first composition.

22. A composite material according to any preceding claim, wherein the fibres of the first composition of dry fibre material are substantially oriented at 135° with respect to the longitudinal reference direction.

23. A composite material according to any preceding claim, wherein the fibres of the second composition of dry fibre material are substantially oriented at 0° with respect to the longitudinal reference direction.

24. A composite material according to any of claims 2 to 23, wherein the fibres of the third composition of dry fibre material are substantially oriented at 45° with respect to the longitudinal reference direction.

25. A composite material according to any of claims 9 to 24, wherein the fibres of the fourth composition of dry fibre material are substantially oriented at 90° with respect to the longitudinal reference direction.

26. A composite material according to any preceding claim, wherein the fibres of the first, second, third, or fourth dry fibre material are uni-directional continuous fibre.

27. A composite material according to any preceding claim, wherein the fibres of the first, second, third, or fourth dry fibre material are carbon fibre.

28. A composite material according to any preceding claim, wherein the fibres of the first, second, third, or fourth dry fibre material are glass fibre.

29. A composite material according to any preceding claim, wherein the curable resin is any one of epoxy resin, polyester resin, phenolic resin, vinyl ester resin or bismaleimide (ΒΜΪ) resin.

30. A composite material according to any preceding claim, wherein the toughening agent comprises a thermoplastic.

31. A structural component for an aircraft comprising the composite material according to anypreceding claim.

32. A structural component for an aircraft according to claim 31, wherein the structural component is an aircraft skin.

33. A structural component according to claim 32, wherein the aircraft skin comprises one or more apertures.

34. A method of forming a composite material, the method comprising the steps of:

providing a first layer on a tool face, the first layer comprising a dry fibre material having fibres arranged at a first angle with respect to a longitudinal reference direction and a toughening agent attached to the dry fibre material, providing a second layer on the first layer, the second layer comprising a dry fibre material having fibres arranged in alignment with the longitudinal reference direction, infusing the assembled stack with a curable resin, and curing the assembled composite material by applying pressure and heat at a temperature sufficient to form a unitary composite material.

35. A composite material substantially as described herein with reference to the accompanying drawings.

Intellectual

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Application No: GB1618191.9 Examiner: Dr Peter Aspinall

Claims searched: 1-34 Date of search: 19 April 2017

Patents Act 1977: Search Report under Section 17

Documents considered to be relevant:

Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-33 WO 2010/035021 A1 (HEXCEL COMPOSITES) see whole document, page 4 lines 23 - page 5 line 24 in particular. X 1-33 US 2006/292375 A1 (MARTIN) See whole document, paragraphs [0004] - [0008] and [0044]-[0046] in particular X 1-27 and 29-33 EP 2532580 A2 (BOEING CO) see whole document, paragraphs [0021],[0025] and [0026] in particular X 1-30 WO 2013/093065 A1 (HEXCEL HOLDING) See whole document, page 9 line 12 - page 10 line 33 in particular.

Categories:

X Document indicating lack of novelty or inventive step A Document indicating technological background and/or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.

Field of Search:

Search of GB, EP, WO & US patent documents classified in the following areas of the UKCX :

Intellectual Property Office is an operating name of the Patent Office www.gov.uk/ipo

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International Classification:

Subclass Subgroup Valid From B32B 0007/00 01/01/2006 B32B 0005/02 01/01/2006 B32B 0005/12 01/01/2006 B32B 0005/28 01/01/2006 B32B 0027/04 01/01/2006 B64C 0001/12 01/01/2006 B64C 0003/26 01/01/2006