Patent Description:
It is known to form composite carbon fibre structures using one or more layers of veil material between layers of carbon fibre ply. Veil materials are typically a low areal weight network of filaments, which are applied between the layers of structural carbon fibre tape or fabric.

Veil materials may consist of one or many types of materials such as thermoplastic, nylon, carbon or glass fibres. The purpose of the layer of veil material is multi-functional. Some of the key uses include improved mechanical performance and properties through toughening mechanisms (improved composite toughness through increased inter-laminar strength and interlayer crack arrestment).

The layer or layers of veil material may also offer composite manufacturing benefits by introducing a stabilising material into the layup. When activated by heat, the veil material lightly bonds together the layers of carbon to create a stabilised uncured material format called a 'stabilized preform', which is able to be handled and subjected to subsequent operations. Stabilising dry fibre tape, woven, braided or stitched fabric formats also allows cutting and physical handling without degrading. An additional benefit of the layer of veil material in the preform is that the separation between reinforcing plies allows for extraction of air and volatiles and, in the case of liquid moulded or resin infused composites, a complete permeation of resin throughout the dry fibre matrix.

The layer or layers of veil material has been traditionally applied to the carbon fibre fabric or tape at the raw commodity material level using operations such as melt bonding, where a sheet of the veil material is laid on top of the fabric and pressed and heated to bond the veil material to one or both sides of the dry fabric. This method is effective for certain manufacturing methods and products, for example large and comparatively flat surfaces such as composite airplane skins. However, this method is less compatible with other manufacturing methods for components having contoured shapes, such as stiffeners, stringers, tubes, ducts, C-section or I-section frames and beams.

One specific application of a layer or layers of veil material is in low pressure resin infused composite manufacturing processes, where low viscosity resins are typically used to maximise resin flow throughout large or complex-shaped dry fibre reinforcements or preforms. Such components, which do not have a layer of veil material, use a tough and high viscosity resin system to achieve desired mechanical properties. Highly viscous resin systems can be processed using a high pressure (autoclave) manufacturing process in order to fully infuse the preform with resin and to cure the composite without defects. Viscous resins may be infused through the preform over short distances, but can be unsuitable for large structures. A high-pressure (autoclave) process can also drive significantly higher recurring and capital costs as compared with a low-pressure material system with a layer of veil material that may be cured using vacuum pressure and an oven or heated tooling equipment.

The abstract of <CIT> states: 'A mandrel for use as a substrate in the manufacture of woven or braided articles may comprise an inner core of foam; at least a first intermediate layer of carbon fiber-reinforced resin; and an outer layer of glass fiber-reinforced resin. The foam core may comprise a high density, closed cell polyurethane foam that is formed of a desired size and shape. The fibers in the intermediate layer and outer layer may be, for example, chopped fibers, continuous longitudinally aligned fibers, circumferentially wound fibers, obliquely aligned fibers, or the fibers may have a woven or braided pattern. Multiple mandrel may be joined together to form complex mandrel shapes such as curves, ovals, and circles.

The abstract of <CIT> states: 'The present invention relates to the production of, in particular, rotationally symmetrical composite components, which are constructed from dry preforms made of reinforcing fibers and then impregnated or infiltrated with liquid resin to form a resin matrix. In particular, the present invention relates to the production of fiber preforms with increased soakability for liquid resin.

The present disclosure is made bearing the above problems in mind.

The present disclosure is generally directed to a method and system for fabricating a composite structure. According to the present invention at least a first layer of veil material is wrapped around one or both sides of a layer of reinforcement material, while the first layer of reinforcement material is positioned on a tool, to produce a first reinforced ply.

The present invention provides a method of fabricating a composite as defined in claim <NUM>.

The method can further comprise placing at least a second layer of reinforcement material on the first layer of veil material while the first reinforced ply is positioned on the tool surface. The method preferably further comprises wrapping at least a second layer of veil material around the second layer of reinforcement material while the second layer of reinforcement material is positioned on the tool, the second layer of reinforcement material and the second layer of veil material forming a second reinforced ply on the first reinforced ply.

The step of placing the first layer of reinforcement material on the tool surface may comprise placing the first layer of reinforcement material on a surface of a mandrel or a forming tool.

The step of wrapping the layer of veil material may comprise relative axial rotation and longitudinal movement between the tool surface and the underlying layer of veil material to spirally wrap the layer of veil material around the underlying layer of reinforcement material. The speed of the relative axial rotation and longitudinal movement between the tool surface and the layer of veil material may be substantially constant during the wrapping so as to provide a substantially constant spacing between, or substantially constant overlap of, adjacent pitches of the layer of veil material. Alternatively the speed of the relative axial rotation and longitudinal movement between the tool surface and the layer of veil material may be varied during the wrapping so as to provide a variable spacing between, or variable overlap of, adjacent pitches of the layer of veil material. The step of wrapping the layer of veil material preferably comprises rotating the tool surface about an axis, whilst keeping the tool surface longitudinally stationary, and longitudinally advancing the layer of veil material. Alternatively, the step of wrapping the layer or layers of veil material may comprise keeping the tool surface axially and longitudinally stationary whilst rotating the veil material axially around the tool surface and longitudinally advancing the layer of veil material.

The tension applied to the layer or layers of veil material may be substantially constant during the wrapping. However the tension applied to the layer or layers of veil material can be varied during the wrapping.

The method can further comprises adding a resin to at least the first reinforced ply to form a composite layup, and curing the resin in the composite layup to form the composite structure. The resin can be infused to form a resin infused composite layup. Alternatively the resin can be injected to form a resin injected composite layup.

The method can further comprise cutting at least the first layer of veil material at the completion of the wrapping at least the first layer of veil material around the first layer of reinforcement material.

The method can further comprise heating at least the first reinforced ply to form at least a first stabilized preform.

According to another aspect, the present disclosure provides a system for fabricating a composite structure as defined in claim <NUM>. A tool having a surface for supporting at least a first layer of reinforcement material placed on the tool surface. A wrapping device configured to wrap at least a first layer of veil material around the first layer of reinforcement material while the first layer of reinforcement material is positioned on the tool to produce a first reinforced ply.

The tool is preferably configured to support at least a second layer of reinforcement material on the first reinforced layer. The wrapping device is preferably configured to wrap at least a second layer of veil material around the second layer of reinforcement material to produce a second reinforced ply on the first reinforced ply.

The system preferably further comprises a drive device configured to cause relative axial rotation and longitudinal movement between the tool and the wrapping device such that the layer of veil material is spirally wrapped around the layer of underlying reinforcement material while the underlying layer of reinforcement material is positioned on the tool. The drive device can be configured to provide a substantially constant speed of the relative axial rotation and longitudinal movement between the tool and the wrapping device so as to provide a substantially constant spacing between, or substantially constant overlap of, adjacent pitches of at least one of the first layer of veil material or the second layer of veil material. The drive device can be configured to provide a variable speed of the relative axial rotation and longitudinal movement between the tool and the wrapping device so as to provide a variable spacing between, or variable overlap of, adjacent pitches of at least one of the first layer of veil material and the second layer of veil material.

The tool can be longitudinally stationary and axially rotatable and the wrapping device is longitudinally advanceable and axially stationary. Alternatively the tool can be longitudinally and axially stationary tool and the wrapping device is longitudinally advanceable and axially rotatable.

The system further comprises a veil material tensioner adapted to apply tension to at least one of the first layer of veil material and the second layer of veil material relative to the tool. The veil material tensioner can be configured to apply a substantially constant tension to at least one of the first layer of veil material and the second layer of veil material relative to the tool. Alternatively the veil material tensioner can be configured to apply a variable tension to at least one of the first layer of veil material and the second layer of veil material relative to the tool.

The system can further comprise a resin supplier configured to add a resin to the first reinforced ply to form a composite layup. A heat source may be configured to heat the composite layup to cure the resin and form the composite structure. A vacuum bag may be configured to contain the composite layup during curing.

The resin supplier may be configured to infuse the resin to form a resin infused composite layup. The resin supplier may be configured to inject the resin to form a resin injected composite layup.

The reinforcement material is preferably formed from carbon fibre.

Alternatively the reinforcement material may include, glass, aramid, silicon carbide, boron, ceramic or metallic fibres.

The present disclosure also relates to a composite structure. At least a first layer of reinforcement material is shaped by a surface of a tool. At least a first layer of veil material is wrapped around the shaped first layer of reinforcement material. The first layer of reinforcement material having the wrapped first layer of veil material forms a first reinforced ply. Resin is added to the first reinforced ply to form an injected composite layup that forms the composite structure after curing the resin.

The resin can be infused to form a resin infused composite layup. Alternatively the resin can be injected to form a resin injected composite layup.

The composite structure can further comprise at least a second layer of reinforcement material positioned around the first reinforced ply and at least a second layer of veil material wrapped around the second layer of reinforcement material, the second layer of reinforcement material having the wrapped second layer of veil material forming a second reinforced ply on the first reinforced ply.

Layer or layers of reinforcement material shaped by the surface of the tool can be shaped on a mandrel.

The reinforcement material can be formed from carbon fibre. Alternatively, the reinforcement material may include, glass, aramid, silicon carbide, boron, ceramic or metallic fibres.

According to an additional aspect, the present disclosure provides a composite structure fabricated in accordance with the method and/or system above.

The present invention will now be described, by way of examples only, with reference to the accompanying drawings wherein:.

The method and system according to the present invention will now be described in detail.

In general, the method of fabricating a composite structure according to the present disclosure include placing at least the first layer of reinforcement material on a surface of a tool. At least the first layer of veil material is wrapped around the first layer of reinforcement material while the first layer of reinforcement material is positioned on a tool to produce a first reinforced ply. A resin is preferably added to at least the first reinforced ply to form a composite layup (also referred to as a "preform"). The resin supplied to the preform is preferably cured to form the composite structure. The terms "composite layup" and "preform" may be used interchangeably herein. The term "stabilized preform" as used herein refers to composite layup (preform) that has been intermediately heated to stabilize the composite layup (preform).

Now referring to <FIG> of the accompanying drawings, a method and system for fabricating a composite structure according to the present invention will be described. The method and system can be used to form a composite part from a layer of reinforcement material, such as a layer of woven or braided carbon fibre material. More specifically, the reinforcement material used with the systems and methods described herein can be formed from carbon fibre and/or include glass, aramid, silicon carbide, boron, ceramic, and/or metallic fibres. As described in more detail below, the layer of reinforcement material can be formed as a continuous tube having open ends such that the layer is a sleeve <NUM>.

As also described in more detail below and as shown in <FIG>, <FIG>, a system <NUM> preferably includes a tool (in the form of a mandrel <NUM>) and a wrapping device <NUM>. The mandrel <NUM> can have a surface <NUM> for supporting at least a first layer <NUM> of reinforcement material placed on the surface <NUM>. The mandrel <NUM> may further be configured to support at least a second layer <NUM> of reinforcement material on a first reinforced ply <NUM> when a composite structure <NUM> (see <FIG>) will include a plurality of layers of reinforcement material.

Further, the mandrel <NUM> can have a shape corresponding to the desired final shape of the composite structure <NUM> formed from the sleeve <NUM>. Depending on the desired shape of the composite structure <NUM> to be made, the mandrel <NUM> can have a rectangular cross-sectional shape, as shown in the Figures, but may have any suitable cross-sectional shape depending on the composite structure being formed. As described below, the mandrel <NUM> can be elongated along an axis 20a. The mandrel <NUM> can be straight, arcuate, or any other suitable shape along a length of the mandrel <NUM>.

The wrapping device <NUM> can be configured to wrap at least a first layer <NUM> of veil material <NUM> around the first layer <NUM> of reinforcement material while the first layer <NUM> of reinforcement material is positioned on the mandrel <NUM> to produce the first reinforced ply <NUM>. When the composite structure will include a plurality of layers of veil material <NUM>, the wrapping device <NUM> is configured to wrap at least a second layer <NUM> of veil material <NUM> around the second layer <NUM> of reinforcement material to produce a second reinforced ply <NUM> on the first reinforced ply <NUM>. The first reinforced ply <NUM> and the second reinforced ply <NUM> on the first reinforced ply <NUM> are referred to as a composite layup (preform). The composite layup (preform) may include more than two reinforced plies.

The mandrel <NUM> and the wrapping device <NUM> can be configured to move relative to each other. For example, the mandrel <NUM> may be longitudinally stationary and axially rotatable, and the wrapping device <NUM> is longitudinally advanceable and axially stationary. Alternatively, the mandrel <NUM> may be longitudinally and axially stationary, and the wrapping device <NUM> is longitudinally advanceable and axially rotatable. It is also contemplated that the mandrel <NUM> and the wrapping device <NUM> may be selectively longitudinally advanceable and axially rotatable to provide any desired relative movement between the mandrel <NUM> and the wrapping device <NUM>.

The system <NUM> can further include a drive device <NUM> configured to cause the above described relative movement between the mandrel <NUM> and the wrapping device <NUM>. More specifically, the drive device <NUM> can be configured to cause relative axial rotation and longitudinal movement between the mandrel <NUM> and the wrapping device <NUM> such that the layer <NUM> and/or <NUM> of veil material is spirally wrapped around the layer <NUM> and/or <NUM> of underlying reinforcement material while the underlying layer <NUM> and/or <NUM> of reinforcement material is positioned on the mandrel <NUM>. The drive device <NUM> can be included in the system <NUM> to provide at least some automation of the manufacture of the composite structure <NUM>.

The drive device <NUM> can be configured to provide a substantially constant speed of the relative axial rotation and longitudinal movement between the mandrel <NUM> and the wrapping device <NUM> so as to provide a substantially constant spacing between, or substantially constant overlap of, adjacent pitches of at least one of the first layer <NUM> of veil material or the second layer <NUM> of veil material. The drive device <NUM> can alternatively or additionally configured to provide a variable speed of the relative axial rotation and longitudinal movement between the mandrel <NUM> and the wrapping device <NUM> so as to provide a variable spacing between, or variable overlap of, adjacent pitches of at least one of the first layer <NUM> of veil material and the second layer <NUM> of veil material. The drive device <NUM> can also be configured to provide substantially constant spacing at one portion of the layer <NUM> and/or <NUM> of veil material and variable spacing at another portion of the layer <NUM> and/or <NUM> of veil material. The drive device <NUM> can include any suitable mechanisms that enable the drive device <NUM> to function as described herein. For example, the drive device <NUM> can include a motor and/or solenoid.

A tensioner <NUM> is positioned with respect to the wrapping device <NUM> and the mandrel <NUM>, such that tensioner <NUM> can apply a tension force to the veil material <NUM> relative to the mandrel <NUM>. The tensioner <NUM> can be configured to apply a substantially constant tension to at least one of the first layer <NUM> of veil material <NUM> and the second layer <NUM> of veil material relative to the mandrel <NUM>. Alternatively or additionally, the tensioner <NUM> may be configured to apply a variable tension to the first layer <NUM> of veil material <NUM> and/or the second layer <NUM> of veil material relative to the mandrel <NUM>. More specifically, the tensioner <NUM> can be configured to apply a substantially constant and/or variable tension to the first layer <NUM> and/or the second layer <NUM> of veil material <NUM> where the layer <NUM> and/or layer <NUM> extends between the wrapping device <NUM> and the mandrel <NUM>. The tensioner <NUM> can be a brake 30a (see <FIG>) controlling a spool <NUM> in the wrapping device <NUM> or can be a spring pulley arrangement 30b (see <FIG>). However, the tensioner <NUM> can be any suitable device that applies a tension force to the first layer <NUM> and/or second layer <NUM> of veil material.

The system <NUM> can also include a cutting device <NUM>, positioned between the spool <NUM> and the tensioner <NUM>. The cutting device <NUM> cuts the veil material <NUM> when the wrapping of the veil material <NUM> for the first layer <NUM> and/or second layer <NUM> is completed. The cutting device <NUM> can be manual, such as scissors, or automated, such as a powered blade or other device.

The system <NUM> can further include a resin supplier <NUM>, a heat source <NUM>, and a vacuum bag <NUM>. The resin supplier <NUM> is preferably configured to add a resin to the composite layup (such as the composite layup <NUM> shown in <FIG>) having at least the first reinforced ply <NUM> and second reinforced ply <NUM>. The resin supplier <NUM> may be configured to infuse or inject the resin to the composite layup <NUM> having the first reinforced ply <NUM> and the second reinforced ply <NUM>. The heat source <NUM> may be configured to heat the first reinforced ply <NUM>, the second reinforced ply <NUM> and resin to cure the resin and form a composite preform or the composite structure <NUM>. During curing, the vacuum bag <NUM> may be configured to surround the first reinforced ply <NUM> or the first and second reinforced plies <NUM>, <NUM> and resin and to apply pressure during heating.

<FIG> is a flow chart of a method <NUM> for fabricating the composite structure <NUM> (shown in <FIG>) according to the present invention. The method <NUM> preferably includes placing <NUM> at least the layer <NUM> of reinforcement material (i.e., sleeve <NUM>) on the surface <NUM> of the mandrel <NUM>. A tension force can be applied <NUM> to the layer <NUM> of reinforcement material (i.e., sleeve <NUM>) to conform the layer <NUM> to the shape of the mandrel <NUM>. For example, when the sleeve <NUM> is used as the layer <NUM> of reinforcement material, tension can be applied <NUM> to the ends 22a, 22b of the sleeve <NUM> to conform the sleeve <NUM> to the shape of the mandrel <NUM> after the layer <NUM> of the reinforcement material <NUM> is placed <NUM> on the mandrel <NUM>. The method <NUM> can further include wrapping <NUM> the veil material <NUM> around the layer <NUM> of reinforcement material while the layer <NUM> of reinforcement material is positioned on the mandrel <NUM> to produce the first reinforced ply <NUM>.

At the completion of the wrapping <NUM>, the veil material <NUM> may be cut <NUM>, for example by the cutting device <NUM>. The placing <NUM>, wrapping <NUM> and cutting <NUM> steps can be repeated as necessary until the desired layers <NUM>, <NUM> of the reinforcement material <NUM> and the layers <NUM>, <NUM> of the veil material <NUM> are built up.

Optionally, the method <NUM> may include performing an intermediate heating step <NUM> on the reinforcement material <NUM> and the veil material <NUM> so as to produce a stabilized preform. The stabilized preform can take the place of the composite layup in the description below when the intermediate heating step <NUM> is performed.

The vacuum bag <NUM> can be placed <NUM> on the one or more of the reinforced plies <NUM>, <NUM> on the mandrel <NUM>. The one or more reinforced plies <NUM>, <NUM> may or may not have been heated to produce a stabilized preform before bagging <NUM>.

Resin <NUM> can be injected or infused <NUM> to form a resin injected composite layup or resin infused composite layup. Heat <NUM> may be applied to cure <NUM> the composite layup into the composite structure <NUM>. The composite structure <NUM> can be trimmed, and the mandrel <NUM> can be removed <NUM> to release the composite structure <NUM>.

Referring now to <FIG>, the method <NUM> (shown in <FIG>) performed using the system <NUM> (shown in <FIG>) will be illustrated. <FIG> shows the tool, in the form of the rectangular cross section elongate mandrel <NUM>. The mandrel <NUM> may be arcuate; however, the mandrel <NUM> can have any suitable shape. The first layer <NUM> of reinforcement material, in the exemplary form of a tubular braided carbon fibre sleeve <NUM>, can be placed <NUM> on the outer surface <NUM> of the mandrel <NUM>, enveloping the mandrel <NUM>. However, the sleeve <NUM> may not completely envelope the mandrel <NUM>, but rather the sleeve <NUM> can at least partially cover the outer surface <NUM> of the mandrel <NUM>. For example, side surfaces of the mandrel <NUM> can be covered by the sleeve <NUM> while the end surfaces of the mandrel <NUM> are not covered by the sleeve <NUM>. The reinforcement material can be in the form of tape, fabric, wound filament, and/or fibreglass formed into the sleeve <NUM> or into another suitable configuration, such as a sheet.

<FIG> shows the sleeve <NUM> being tensioned <NUM> to conform the sleeve <NUM> to the shape of the outer surface of the mandrel <NUM>. More specifically, lateral force can be applied relative to each end of the sleeve <NUM> by pulling the ends away from each other. The lateral force applied elongates the sleeve <NUM> and circumferentially shrinks the sleeve <NUM> onto the outer surface <NUM> of the mandrel <NUM>. The lateral force can be applied manually by gripping ends 22a and 22b of the sleeve <NUM> and extending the sleeve <NUM> along an axis 22c aligned with a length-wise direction of the sleeve <NUM>. For example, the first end 22a of the sleeve <NUM> can be restrained, for example by clamping, and the second end 22b of the sleeve can be pulled away from the first end 22a along the axis 22c. An automated device can also be used to apply the relative lateral forces to the ends 22a and/or 22b of the sleeve <NUM> to extend the sleeve <NUM> along the axis 22c and apply a tension load to the sleeve <NUM>.

<FIG> shows veil material, in the form of a roll of veil material <NUM> wound onto a spool <NUM>, being wrapped <NUM> around the sleeve <NUM>. More specifically, the veil material <NUM> can be wrapped around the sleeve <NUM> while the sleeve <NUM> is positioned on the mandrel <NUM>. As shown in <FIG>, the mandrel <NUM> and sleeve <NUM> may remain longitudinally stationary whilst the drive device <NUM> axially rotates the mandrel <NUM> and the sleeve <NUM>. A spool <NUM> of the veil material <NUM> can be longitudinally advanced relative to the mandrel <NUM> and sleeve <NUM> by the drive device <NUM> to spirally wrap the veil material <NUM> around the sleeve <NUM>. Alternatively the spool <NUM> can remain longitudinally stationary and the drive device <NUM> moves the mandrel <NUM> and sleeve <NUM> longitudinally relative to the spool <NUM>.

The cutting device <NUM> may cut <NUM> the veil material <NUM> when the wrapping of the sleeve <NUM> is completed.

The steps shown in <FIG> can be repeated to build up a desired thickness of the composite layup <NUM> (shown in <FIG> and described below). During the wrapping step <NUM>, shown in <FIG>, the speed of the relative axial rotation and the relative longitudinal movement between the mandrel <NUM> and the sleeve <NUM> relative to the veil material <NUM> can be maintained substantially constant during the wrapping. By maintaining a substantially constant speed, a substantially spacing between adjacent pitches of the veil material <NUM> is achieved. As an alternative or addition, a substantially constant overlap of the adjacent pitches of veil material <NUM> can be achieved.

The speeds of the relative axial rotation and the relative longitudinal movement between the mandrel <NUM> and the sleeve <NUM> can also be varied during the wrapping so as to provide a variable spacing, or variable overlap, of adjacent pitches of the veil material <NUM>. The latter allows the amount of veil material <NUM> applied to be varied so as to for example, provide areas of relatively higher strength and relatively lower strength within the composite structure. Alternatively or additionally, the veil material <NUM> can be applied to a part of the sleeve <NUM> at a constant speed and to another part of the sleeve <NUM> at a variable speed.

<FIG> shows that, during wrapping <NUM>, tension can be applied to the veil material <NUM>, at region <NUM> of the veil material <NUM>, using brake 30a torque in the spool <NUM> as the tensioner <NUM>, to resist unspooling. As an alternative, <FIG> shows a spring pulley arrangement 30b, used as the tensioner <NUM> to apply tension to the veil material <NUM> in the region <NUM>. The magnitude of the tension force can be maintained constant during the entire wrapping process and/or can be varied at different time periods during the wrapping process in order to best suit the application of the veil material <NUM> to the sleeve <NUM>. More particularly, the tension applied to the veil material <NUM> as the veil material <NUM> can be wrapped around each layer <NUM>, <NUM> of the reinforcement material is controlled to ensure desired application and coverage of each layer <NUM>, <NUM> of the reinforcement material. The controlling of the tension in turn controls features and properties such as the thickness and morphology of the layer <NUM>, <NUM> of the veil material <NUM>. The morphology is the structure of the filaments in the network of the veil material <NUM>.

The location of the veil material <NUM> is also controlled as the veil material <NUM> is applied to the reinforcement material to ensure desired control of the coverage of the veil material <NUM> within each layer. In the case of automated layup, an exemplary method of controlling the location would be through accurate indexing and locating of the mandrel <NUM> or holding the veil material <NUM> with respect to the tooling holding the mandrel <NUM>. The indexing and locating may follow a predetermined path to apply the veil material <NUM> at a fixed translation speed relative to the mandrel <NUM> and feed rate of the veil material <NUM> as the veil material <NUM> is unspooled from the spool <NUM>.

Alternatively a real-time automated system that uses visual tracking and active feedback to control the application and location of the veil material <NUM> as the veil material <NUM> is wrapped around the layer <NUM> or layers <NUM>, <NUM> of reinforcement material. Visual tracking could be used to detect and control features such as the edges of the veil material <NUM> with respect to the edge of the previous spiral applied to the reinforcement material, or detection of the applied layer of veil material <NUM> using for example the contrast between veil and un-covered (bare) reinforcement material. The visual tracking could be achieved using optical tracking using a camera either mounted on a robot or alternatively a fixed camera mounted separately to both the mandrel <NUM> and a robot. In both cases, the use of software allows for active tracking and feedback for the location of the veil material <NUM> as the veil material <NUM> is applied on the layer <NUM> or layers <NUM>, <NUM> of reinforcement material.

<FIG> shows the mandrel <NUM> after the wrapping <NUM> of the veil material <NUM> is complete to thus form at least a first layer <NUM> of veil material <NUM> on the layer <NUM> of reinforcement material. The layer <NUM> of veil material <NUM> on the layer <NUM> of reinforcement material can form the reinforced ply <NUM>. One or more reinforced plies <NUM>, <NUM> may form the composite layup. <FIG> also shows the wrapped mandrel <NUM> after placement <NUM> within a vacuum bag <NUM>.

An optional intermediating heating step <NUM> can be performed to create a stabilized preform (e.g., a stabilised, uncured composite layup) from the at least one reinforced ply <NUM> and/or <NUM> or from the composite layup <NUM>. The first reinforced ply <NUM> can be made into a first stabilized preform using an intermediate heating cycle, and then the second reinforced ply <NUM> can be applied to the first stabilized preform. Alternatively, the composite layup <NUM> of a plurality of reinforced plies <NUM>, <NUM> can be formed, then the reinforced plies <NUM>, <NUM> can together be made into a stabilized preform using an intermediate heating cycle. As used herein, an "intermediate heating cycle" is a heating cycle that does not fully cure the composite layup <NUM> to make the final composite structure <NUM>.

<FIG> shows the injection <NUM> or infusion <NUM> of a resin <NUM> to form a resin injected composite layup or resin infused composite layup respectively. <FIG> also shows the application of heat <NUM> to cure <NUM> the resin and the composite layup into the composite structure <NUM> (shown in <FIG>).

<FIG> shows an exemplary pair of the composite structures <NUM> produced after the resin <NUM> has cured <NUM> and after trimming and removal <NUM> of the mandrel <NUM>. The pair of composite structures <NUM> is one example of a composite structure <NUM> that can be formed using the system <NUM> and method <NUM> described herein.

Turning now to <FIG>, there is shown the composite structure <NUM> that can be manufactured using the system <NUM> and method <NUM> described herein. The composite structure <NUM> includes at least the first layer <NUM> of reinforcement material <NUM> shaped by the surface <NUM> of the mandrel <NUM>, and at least the first layer <NUM> of veil material wrapped around the shaped first layer <NUM> of reinforcement material. The first layer <NUM> of reinforcement material having the wrapped first layer <NUM> of veil material can form the first reinforced ply <NUM>. Resin can be added to the first reinforced ply <NUM> to form the composite structure <NUM> after curing the resin.

When the composite structure <NUM> is layered, the composite structure <NUM> preferably includes at least the second layer <NUM> of reinforcement material positioned around the first reinforced ply <NUM> and at least the second layer <NUM> of veil material wrapped around the second layer <NUM> of reinforcement material. The second layer <NUM> of reinforcement material having the wrapped second layer <NUM> of veil material can form the second reinforced ply <NUM> on the first reinforced ply <NUM>. The layer <NUM> and/or layer <NUM> of reinforcement material may be shaped by the surface <NUM> of the mandrel <NUM>, when the mandrel <NUM> is used as the tool. The resin can be infused or injected to the reinforced ply <NUM> and/or <NUM>.

At least some possible advantages of the system and method described above is that they provide improved and tailorable mechanical properties and toughness (thereby offering more weight efficient aircraft structures) through the use of the later or layers of the veil material, which is also able to be manufactured using lower cost and automatable manufacturing methods, specifically with low viscosity resin systems and low pressure (non-autoclave) curing methods. This reduces the fabrication cost of composite structures, such as composite parts, as the method and system described herein avoid the traditionally complex manual layup process.

Claim 1:
A method (<NUM>) of fabricating a composite structure (<NUM>), said method comprising the steps of:
placing (<NUM>) at least a first layer (<NUM>) of dry reinforcement material on a surface (<NUM>) of a tool (<NUM>), and
wrapping (<NUM>) at least a first layer (<NUM>) of veil material (<NUM>) around the first layer of reinforcement material while the first layer of reinforcement material is positioned on the tool to produce a first reinforced ply (<NUM>),
further comprising applying tension to the veil material.