Patent Description:
A current method for fabricating composite structures utilises a resin infusion process to infuse a composite preform, formed of multiple plies formed of composite fibres, with resin prior to curing of the resin to form a composite structure. According to a current method, the composite preform is located on a tool surface and a vacuum bagging film is placed over the tool surface to cover the composite preform and sealed to form a sealed chamber between the tool surface and vacuum bagging film. Resin is infused through the composite preform by application of vacuum pressure to a downstream end of the sealed chamber, drawing resin from an upstream resin supply through the composite preform. Once the resin has been infused throughout the preform, the entire assembly is heated, typically in an oven, to cure the resin and thus form the composite structure.

Resin infuses through the composite preform with a wavefront that may or may not progress evenly across the lateral extent of the preform. It is important to ensure that the entire preform is infused, whilst avoiding resin that has passed through the preform in advanced areas of the wavefront from being drawn into the vacuum source. If resin is drawn into the vacuum source, there is a risk of damage to the vacuum source. The cost of removing cured resin from the vacuum source and associated vacuum piping between the tool and vacuum source, or replacing the vacuum source or piping, may also be prohibitive.

Various solutions to this problem have previously been proposed, with varying success in terms of effectiveness, finished product quality, retrofittability and cost.

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

<CIT>, in accordance with its abstract, states "In order to provide a process for the production of a component consisting of a fiber reinforced material, with which liquid resin is supplied to a semifinished fiber article by way of application by vacuum pressure, it is provided for a heat curing resin to be used as resin and for application by vacuum pressure and temperature to be controlled such that in relation to the liquid resin the boiling point curve of the resin is not exceeded".

The present disclosure is generally directed to a method of resin infusing a composite preform and a resin infusion system for resin infusing a composite preform. According to embodiments of the present disclosure, a resin reservoir element is utilised to collect excess resin that has passed through the resin flow path beyond the composite preform, upstream of the vacuum source. The resin reservoir element is located on an upper tool surface of the tool on which the composite preform is located, defining a resin reservoir for collection of the excess resin.

According to one aspect, the present disclosure provides a method of resin infusing a composite preform. A composite preform is located on an upper tool surface of a tool. A resin reservoir element is located on the tool surface on a downstream side of the composite preform. The resin reservoir element and tool surface define a resin reservoir. The resin reservoir has a reservoir outlet and a reservoir inlet located between the tool surface and the reservoir outlet. A vacuum bagging film is placed over the tool surface to cover the composite preform and resin reservoir element. The vacuum bagging film is sealed relative to the tool surface to define a sealed resin infusion chamber between the tool surface and the vacuum bagging film. The composite preform and resin reservoir element are located in the resin infusion chamber. A resin supply is provided. A resin flow path is provided from the resin supply to the resin infusion chamber on an upstream side of the composite preform, through the composite preform and through the reservoir inlet to the resin reservoir. At least partial vacuum pressure is applied to the reservoir outlet to establish a pressure differential between the resin supply and the reservoir outlet to drive resin from the resin supply through the resin flow path, infusing the composite preform with resin and collecting excess resin in the resin reservoir. In accordance with claim <NUM>, a resin flow control choke is located in the resin flow path between the composite preform and the resin reservoir.

In one or more preferred embodiments, the resin reservoir element comprises a channel having a first lower edge located toward the composite preform and an opposing second lower edge located away from the composite preform. A gap is formed between the first lower edge and the tool surface to define the reservoir inlet.

The method may further comprise locating a first permeable flow media between the first lower edge and the tool surface to at least partially define the gap.

The method may further comprise comprising removably sealing the second lower edge relative to the tool surface.

In one or more preferred embodiments, the resin reservoir element is located so as to extend along at least a majority of the length of a downstream edge of the composite preform.

The method may further comprise providing a second permeable flow media between the reservoir outlet and a vacuum outlet port extending from the tool surface through the tool to define a vacuum flow path. At least partial vacuum pressure may be applied through the vacuum flow path.

Also disclosed a method of forming a composite article. The method comprises resin infusing a composite preform according to the method defined above to form a resin infused composite preform and curing the resin infused composite preform.

Following curing of the resin infused composite preform, the resin reservoir element may be removed from the tool surface. Excess resin collected in the reservoir may then be removed from the resin reservoir element.

According to a second aspect, the present disclosure provides a resin infusion system for resin infusing a composite preform. The system includes a tool having an upper tool surface receiving a composite preform to be resin infused and a resin supply. A resin reservoir element is located on the tool surface on a downstream side of the composite preform. The resin reservoir element and tool surface define a resin reservoir having a reservoir outlet and a reservoir inlet located between the tool surface and the reservoir outlet. A vacuum bagging film covers the composite preform and the resin reservoir element to define a sealed resin infusion chamber between the vacuum bagging film and the tool surface. The composite preform and resin reservoir element are located in the resin infusion chamber. A resin flow path extends from the resin supply to the resin infusion chamber on an upstream side of the composite preform, through the composite preform and through the reservoir inlet to the resin reservoir. A vacuum source communicates with the reservoir outlet via a vacuum flow path. In accordance with claim <NUM>, the system comprises a permeable resin flow control choke located in the flow path between the composite preform and the resin reservoir.

In one or more preferred embodiments, the resin reservoir element comprises an elongate inverted channel section having closed opposing ends.

The channel section may have a first lower edge located toward the composite preform and an opposing second lower edge located away from the composite preform. In this configuration, the reservoir inlet may comprise a gap between the first lower edge and the tool surface.

The system may further comprise a first permeable flow media located between the first lower edge and the tool surface to at least partially define the gap.

The second lower edge of the channel section may be removably sealed to the tool surface.

In a preferred embodiment, the channel section has a generally semi-circular cross-section.

The reservoir outlet may advantageously be located at or adjacent an uppermost portion of the resin reservoir element.

In a preferred embodiment, the resin reservoir element extends along at least a majority of the length of a downstream edge of the composite preform.

In one or more preferred embodiments the vacuum flow path extends through a vacuum outlet port extending from the tool surface through the tool and a second permeable flow media extends from the reservoir outlet to the vacuum outlet port. In this configuration, the vacuum bagging film extending over the second permeable flow media and the vacuum outlet port.

In one or more embodiments, a plurality of the reservoir outlets are spaced along the resin reservoir element.

The features described above may be implemented independently in various embodiments of the present disclosure or may be combined in yet other embodiments as will be appreciated by persons skilled in the art. This statement does not change the fact that the scope of protection is defined by the claims.

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

Methods and systems according to exemplary embodiments of the present disclosure will now be described in detail. In general, methods of resin infusing a composite preform according to the present disclosure include locating a composite preform on an upper tool surface of a tool. A resin reservoir element is located on the tool surface on a downstream side of the composite preform. The resin reservoir element and tool surface define a resin reservoir which has a reservoir outlet and a reservoir inlet that is located between the tool surface and the reservoir outlet, thus locating the reservoir outlet at a position higher than the reservoir inlet. A vacuum bagging film is placed over the tool surface to cover both the composite preform and the resin reservoir element. The vacuum bagging film is sealed relative to the tool surface to define a sealed resin infusion chamber between the tool surface and vacuum bagging film, with the composite preform and resin reservoir element located in the resin infusion chamber. A single vacuum bagging film may be utilized. A double vacuum bagging film configuration is also envisaged, with an outer vacuum bagging film located over an inner vacuum bagging film, with breather material located therebetween. A resin flow path is provided from a resin supply to the resin infusion chamber on an upstream side of the composite preform, through the composite preform and through the reservoir inlet to the resin reservoir. At least partial vacuum pressure is applied to the reservoir outlet to establish a pressure differential between the resin supply and reservoir outlet to drive resin from the resin supply through the resin flow path, particularly through the composite preform, thereby infusing the composite preform with resin. For a double vacuum bagging film configuration, at least partial vacuum pressure may also be applied to the cavity between the inner and outer vacuum bagging films. Excess resin that passes through the composite preform prior to turning off the vacuum source is collected in the resin reservoir. The resin infused composite preform may then be cured, typically within a heated oven. Excess resin collected in the reservoir will typically cure within the resin reservoir. Following curing, and disassembly of the system by removal of the vacuum bagging film(s) and associated consumables, the resin reservoir element may be removed from the tool and either discarded or cleaned of the cured resin collected in the resin reservoir.

Now referring to <FIG> of the accompanying drawings, a system <NUM> for resin infusing a composite preform <NUM>, according to a first embodiment, will now be described. The system <NUM> has a tool <NUM> having an upper tool surface <NUM> on which the composite preform <NUM> to be resin infused is located. A resin reservoir element <NUM> is located on the tool surface <NUM> on a downstream side of the composite preform <NUM>. In the context of the present specification, upstream and downstream sides of the composite preform <NUM> are identified with reference to the direction of flow of resin, as will be further described. Referring particularly to <FIG>, the reservoir element <NUM>, together with the tool surface <NUM>, defines a resin reservoir <NUM> having a reservoir outlet <NUM> and a reservoir inlet <NUM> located between the tool surface <NUM> and the reservoir outlet <NUM>. A vacuum bagging film <NUM> covers the composite preform <NUM> and the resin reservoir element <NUM> to define a sealed resin infusion chamber <NUM> between the vacuum bagging film <NUM> and the tool surface <NUM>. The composite preform <NUM> and resin reservoir element <NUM> are located in the resin infusion chamber <NUM>. The system <NUM> further comprises a resin supply <NUM> with a resin flow path <NUM> extending from the resin supply <NUM> to the resin infusion chamber <NUM> on an upstream side of the composite preform <NUM>, through the composite preform <NUM> and through the reservoir inlet <NUM> into the resin reservoir <NUM>. Referring to <FIG>, a first vacuum source <NUM> communicates with the reservoir outlet <NUM> via a vacuum flow path <NUM>.

The tool <NUM> may be formed of any of various structural materials, including mild steel, stainless steel, invar or a carbon composite material that will maintain its form at elevated temperatures associated with curing, so as to provide a geometrically stable tool surface <NUM> though the resin curing process. The tool surface <NUM> may be substantially flat for the production of composite structures having a substantially flat lower surface, such as wing or fuselage skin panels, or otherwise shaped as desired so as to provide a shaped surface of a non-planar composite structure.

The composite preform <NUM> may take any form suitable for resin infusion and as dictated by the geometric and structural requirements of the laminated composite structure to be fabricated. The composite preform <NUM> may comprise a layup of multiple plies of reinforcing material, each formed of woven or braided fibres and/or chopped strand mat. The preform plies may be formed of any of various reinforcing fibres, such as carbon, graphite, glass, aromatic polyamide or any other suitable material for forming a resin reinforced laminated composite structure. The plies may form a dry preform, without any resin, or alternatively the preform may have some pre-existing resin content prior to the resin infusion process. The composite preform <NUM> is located on the tool surface <NUM> with the lower surface of the preform <NUM> oriented on the tool surface <NUM> such that the lower surface of the resulting cured composite structure will match the form of the tool surface <NUM>. The composite preform <NUM> located on the tool surface <NUM> has a laterally extending downstream edge <NUM>, an opposing laterally extending upstream edge <NUM> and opposing longitudinally extending side edges <NUM>. The preform <NUM> may take any desired shape corresponding to the shape of the laminated composite structure to be formed.

The resin reservoir element <NUM>, in the exemplary first embodiment depicted, comprises an elongate inverted channel section <NUM> with closed opposing ends <NUM>. In the first embodiment depicted, the channel section <NUM> has a generally semi-circular cross-section, however it is envisaged that the channel section <NUM> may take any of various alternate forms, including rectangular, square, triangular, semi-hexagonal or any of various other cross-sectional shapes. A semi-circular cross-section is advantageous in that it does not present any sharp edges on its outer surface which may otherwise puncture the vacuum bagging film <NUM> or be difficult to seal. A channel section <NUM> with a semi-circular cross-section may also typically be inexpensive to form, able to be formed by cutting a tubular section in half and to length. The resin reservoir element <NUM> may be formed of any of various materials, including metallic materials such as stainless steel or aluminium or other non-metallic materials including composite materials or thermosetting plastics that preferably maintain their shape at elevated temperatures associated with the resin curing process. The closed opposing ends <NUM> of the resin reservoir element <NUM> may be integrally formed with the channel section <NUM> or otherwise secured to the ends of the channel section <NUM>, such as by bonding and/or mechanical fastening. The opposing ends <NUM> of the resin reservoir element <NUM> may be formed of the same material as that of the channel section <NUM>. Alternatively, the opposing ends <NUM> of the resin reservoir element <NUM> may be formed of a material different to that from which the channel section <NUM> is formed.

In one modified form <NUM>' of the system <NUM> of the first embodiment, as depicted in <FIG>, the opposing ends <NUM>' of a modified resin reservoir element <NUM>' are formed from multiple pieces of sealing tape, as otherwise used to seal the vacuum bagging film <NUM> and other components of the system, as will be further described below. In this modified form, the resin reservoir element <NUM>' may be simply formed from a cut length of a channel section <NUM>', which may be located on the tool surface <NUM> with the ends of the defined resin reservoir then sealed with the use of sealing tape to form the closed opposing ends <NUM>' of the resin reservoir element <NUM>'.

Referring to <FIG>, in the first embodiment, the resin reservoir element <NUM> is located on the tool surface <NUM> so as to extend along at least a majority of the length of the downstream edge <NUM> of the composite preform <NUM>. Having the resin reservoir element <NUM> formed of a sufficient length to extend along at least a majority of the length of the downstream edge <NUM> of the composite preform <NUM> provides a relatively direct flow path from along the downstream edge <NUM> of the composite preform <NUM> into the resin reservoir <NUM> along the downstream edge <NUM>. In configurations where the downstream edge <NUM> of the composite preform <NUM> is linear, the resin reservoir element <NUM> may advantageously be arranged generally parallel to the downstream edge <NUM> of the composite preform <NUM>.

As depicted in <FIG> and <FIG>, in the first embodiment two reservoir outlets <NUM> are provided, spaced along the channel section <NUM>. It is also envisaged that a single reservoir outlet <NUM> only may be provided. Alternatively, three or more reservoir outlets <NUM> may be provided, spaced along the channel section <NUM>. The reservoir outlets <NUM> may advantageously be located at or adjacent an uppermost portion of the resin reservoir element <NUM>. In the embodiment depicted, the reservoir outlets <NUM> are located at the top of the channel section <NUM>, as best depicted in <FIG> and <FIG>, so as to maximize the vertical separation between the reservoir inlet <NUM> and reservoir outlets <NUM>.

Referring to <FIG> and <FIG>, in the system <NUM> of the first embodiment, the channel section <NUM> of the resin reservoir element <NUM> has a first lower edge <NUM> located toward the downstream edge <NUM> of the composite preform <NUM> and an opposing second lower edge <NUM> located away from the composite preform <NUM>, such that the first lower edge <NUM> is effectively the upstream edge and the second lower edge <NUM> is effectively the downstream edge. In the particular configuration depicted, the reservoir inlet <NUM> is defined by a gap formed between the first lower edge <NUM> and the tool surface <NUM>. In the embodiment depicted, a laterally extending first strip <NUM> of permeable flow media and a downstream portion <NUM> of a permeable peel ply <NUM> (which itself constitutes a permeable flow media) placed over the preform <NUM> (as will be further discussed below) extend into, and define, the gap defining the reservoir inlet <NUM>. The first strip <NUM> and downstream portion <NUM> of the peel ply <NUM> support the first lower edge <NUM> of the channel section <NUM>. The first strip <NUM> of permeable flow media and downstream portion <NUM> of the peel ply <NUM> are sufficiently permeable to allow resin to pass therethrough into the reservoir inlet <NUM>. The first strip <NUM> of permeable flow media may suitably be in the form of a nylon mesh material, such as PLASTINET®<NUM> available from Airtech International Inc, or any other highly permeable media enabling passage of resin therethrough. The peel ply <NUM> also constitutes a permeable flow media, and may suitably be in the form of a PTFE coated fibreglass fabric, such as RELEASE EASE® <NUM> also available from Airtech International Inc, or any other permeable peel ply material.

It is envisaged that either the first strip <NUM> of permeable flow media or downstream portion <NUM> of the peel ply <NUM> may be omitted, leaving a single permeable flow media to define the gap of the reservoir inlet <NUM>. It is still further envisaged that the reservoir inlet <NUM> may be defined by one or more apertures provided along the length of the resin reservoir element <NUM>, although the arrangement depicted avoids the need for drilling or otherwise forming such apertures in the resin reservoir element <NUM>.

The second lower edge <NUM> of the channel section <NUM> may be removably sealed relative to the tool surface <NUM>, and in the embodiment depicted is removably sealed by way of a strip <NUM> of sealing tape, which may conveniently be in the form of a mastic sealant tape, such as GS-<NUM>-<NUM> sealant tape available from Airtech International Inc.

The resin flow path <NUM> extending from the resin supply <NUM>, through the resin infusion chamber <NUM>, composite preform <NUM> and reservoir inlet <NUM> into the resin reservoir <NUM> is comprised of a series of plumbing elements and consumable layup materials. The upstream portion of the resin flow path <NUM> may comprise one or more resin supply pipes <NUM> communicating with one or more resin infusion inlets <NUM> extending through the tool <NUM> on the upstream side of the composite preform <NUM>, delivering resin to the resin infusion chamber <NUM> on the upstream side of the composite preform <NUM>. The resin supply pipes <NUM> are typically formed of copper.

The mid portion of the resin flow path <NUM> is formed by the composite preform <NUM>, the peel ply <NUM> and a layer <NUM> of permeable flow media. The peel ply <NUM> extends over the entirety of the composite preform <NUM>, beyond each of the edges <NUM>, <NUM>, <NUM> of the composite preform <NUM>. The peel ply <NUM> serves both to prevent the layer <NUM> of permeable flow media from sticking to the composite preform <NUM> and to provide a path for infusion of resin into the composite preform <NUM>, both along the upstream edge <NUM> of the composite preform <NUM> and through the upper surface of the composite preform <NUM>. The layer <NUM> of permeable flow media, which in the embodiment depicted is formed of the same material as the first strip <NUM> of permeable flow media, extends over the peel ply <NUM>. In the embodiment depicted, the layer <NUM> of permeable flow media extends beyond the upstream edge <NUM> of the composite preform <NUM> over the one or more resin infusion inlet ports <NUM> and beyond the downstream edge <NUM> of the composite preform <NUM>, leaving a gap between the downstream edge of the layer <NUM> of permeable flow media and the strip <NUM> of permeable flow media. Rather than communicating the resin infusion chamber <NUM> with the resin supply <NUM> through a resin flow path <NUM> passing through the resin inlet port <NUM> extending through the tool <NUM>, it is also envisaged that the resin flow path <NUM> could pass through the vacuum bagging film <NUM>. In such a configuration an aperture may be formed in the vacuum bagging film <NUM> and communicated with the resin supply <NUM>, sealing around the aperture.

The downstream portion of the resin flow path <NUM> is formed by the downstream portion <NUM> of the peel ply <NUM> and the strip <NUM> of permeable flow media.

The vacuum flow path <NUM> communicating the first vacuum source <NUM> with the reservoir outlets <NUM> is comprised of a series of plumbing elements and consumable layup materials. The upstream portion of the vacuum flow path <NUM> extending from the reservoir outlets <NUM> comprises a second permeable flow media. The second permeable flow media may conveniently be formed of the same material as the layer <NUM> and strip <NUM> of permeable flow media used in the resin flow path <NUM>, however it is also envisaged that other forms of permeable flow media may be utilised as desired. The second permeable flow media here comprises two strips <NUM> of permeable flow media located on the resin reservoir element <NUM>, each covering one of the reservoir outlets <NUM>, and a laterally extending further strip <NUM> of permeable flow media that communicates the strips <NUM> with a vacuum outlet port <NUM> extending through the tool <NUM> downstream of the resin reservoir element <NUM>. Tape <NUM> may be applied to the exposed faces of the strip <NUM> of sealing tape sealing the resin reservoir element <NUM> to the tool surface <NUM> so as to prevent the strips <NUM>, <NUM> of second permeable flow media from sticking to the strip <NUM> of sealing tape. The vacuum outlet port <NUM> communicates with the first vacuum source <NUM> by way of one or more vacuum outlet pipes <NUM>, forming the downstream portion of the vacuum flow path <NUM>. The vacuum outlet pipes <NUM> are typically formed of copper. Rather than communicating the reservoir outlets <NUM> with the first vacuum source <NUM> through a vacuum flow path <NUM> passing through the vacuum outlet port <NUM> extending through the tool <NUM>, it is also envisaged that the vacuum flow path <NUM> could pass through the vacuum bagging film <NUM>. In such a configuration an aperture may be formed in the vacuum bagging film <NUM> and communicated with the first vacuum source <NUM>, sealing around the aperture.

The vacuum bagging film <NUM> extends over the entire layup formed by the composite preform <NUM>, peel ply <NUM> and layer <NUM> of permeable flow media and further extends over the resin reservoir element <NUM> and strips <NUM>, <NUM> of second permeable flow media. Any of various vacuum bagging film materials may be utilized, including but not limited to Airtech WL7400 or SL800 vacuum bagging films available from Airtech International Inc. The vacuum bagging film <NUM> is sealed relative to the tool surface <NUM> about the periphery of the vacuum bagging film <NUM> by way of further strips <NUM> of sealing tape, typically formed of the same material as the strip <NUM> of sealing tape sealing the second lower edge <NUM> of the channel section <NUM> to the tool surface <NUM>. Additional strips <NUM> of sealing tape seal the vacuum bagging film <NUM> to the resin reservoir element <NUM> about the strips <NUM> of second permeable flow media to isolate the resin infusion flow path <NUM> and resin infusion chamber <NUM> from the vacuum flow path <NUM>. As may be best appreciated from <FIG> and <FIG>, the vacuum bagging film <NUM> defines the upper boundary of the resin flow path <NUM>. In between the downstream edge of the layer <NUM> of permeable flow media and the upstream edge of the strip <NUM> of permeable flow media, the vacuum bagging film <NUM> restricts the resin flow path <NUM> to the downstream portion <NUM> of the peel ply <NUM>, which defines a permeable resin flow control choke. The vacuum bagging film <NUM> also defines the upper boundary of the vacuum flow path <NUM>.

In use, once the system <NUM> has been assembled as discussed above, the resin supply <NUM> is catalyzed and heated to bring the resin to a suitable resin infusion temperature. Typically the entire system is heated within an oven that is also used for subsequent curing. The temperature for resin infusion will be dependent upon the resin system utilised, and will typically be selected to provide a suitable viscosity enabling the resin to be infused through the resin flow path <NUM>. Any resin suitable for use in resin infusion processes, and as dictated by desired characteristics of the composite structure to be formed, may be utilised. Suitable resins may include epoxy, bismaleimide, benzoxazine, polyimide and polyamide-imide resins. At least partial vacuum pressure is applied to the reservoir outlet <NUM>, via the first vacuum source <NUM> and vacuum flow path <NUM>. A smaller partial vacuum (i.e., a higher absolute pressure) may also be applied to the resin supply <NUM>, by way of a second vacuum source <NUM> connected to a second vacuum pipe <NUM>, as best shown in <FIG>. Where partial vacuum is applied to the resin supply <NUM> by the second vacuum source <NUM>, a pressure differential may be maintained between the first vacuum source <NUM> and second vacuum source <NUM> such that the absolute pressure at the reservoir outlet <NUM> applied by the first vacuum source <NUM> is lower than the absolute pressure at the resin supply <NUM>. In one example, a full vacuum (<NUM> mBar / <NUM> kPA) may be applied by the first vacuum source <NUM> and a higher pressure / lower vacuum of <NUM> to <NUM> mBar (<NUM> to <NUM> kPA) may be applied by the second vacuum source <NUM>, thereby providing a pressure differential of the same amount driving resin from the resin supply <NUM> through the resin flow path <NUM>. Full vacuum pressure may also be applied to the second vacuum source <NUM> prior to resin infusion to degas the resin.

Maintaining at least partial vacuum on the resin supply <NUM> ensures at least a partial vacuum is maintained throughout the resin infusion chamber <NUM>. Atmospheric pressure acting on the preform <NUM> through the vacuum bagging film <NUM>, the layer <NUM> of permeable flow media and the peel ply <NUM> acts to consolidate the composite preform <NUM>. Resin moves through the resin infusion chamber <NUM> along a wave front, through the layer <NUM> of permeable flow media, which will generally have a greater permeability than both the peel ply <NUM> and the composite preform <NUM>, thus forming the path of least resistance. Resin passing through the layer <NUM> of permeable flow media will infuse down through the less permeable peel ply <NUM> and into the preform <NUM>. Some resin will also flow laterally through the upstream edge <NUM> of the composite preform <NUM> and, to a lesser degree, through the opposing side edges <NUM> of the composite preform <NUM>. Having the downstream edge <NUM> of the layer <NUM> of permeable flow media finish short of both the strip <NUM> of permeable flow media and the downstream portion <NUM> of the peel ply <NUM> prevents resin bypassing the preform <NUM> and simply being drawn through the layer <NUM> of permeable flow media directly into the resin reservoir <NUM>. The rate of advance of the resin wave front is inhibited by forcing the resin to pass downstream longitudinally through the permeable resin flow control choke defined by the downstream portion <NUM> of the peel ply <NUM> once it passes the downstream edge <NUM> of the composite preform <NUM> and the downstream edge of the layer <NUM> of permeable flow media, prior to reaching the resin reservoir <NUM>. Rather than forming the permeable resin flow control choke with the downstream portion <NUM> of the peel ply <NUM>, it is also envisaged that a separate permeable resin flow control choke, typically formed of a permeable media of reduced permeability as compared to the layer <NUM> of permeable control media, may be utilised between the composite preform <NUM> and the resin reservoir <NUM> to control advance of the resin wave front.

The resin wave front will typically not advance evenly across the lateral extent of the composite preform <NUM>, particularly where there are non-uniform geometries or thickness of the composite preform <NUM>. Where a region of the resin wave front first reaches the reservoir inlet <NUM>, resin will flow into the resin reservoir <NUM>. With vacuum being drawn through the resin outlets <NUM>, located higher than the reservoir inlet <NUM>, gravity acting on the resin will result in the resin not tending to be drawn through the reservoir outlets <NUM> and along the vacuum flow path <NUM> toward the first vacuum source <NUM>. Resin infusion may thus continue without resin being driven into the vacuum pipe <NUM> until visual confirmation is received that the entire resin wave front has reached the downstream edge <NUM> of the composite preform <NUM>, thus indicating complete resin infusion of the composite preform <NUM>. Once completion of resin infusion has been visually identified, a resin inlet valve (not depicted) on the resin supply pipe <NUM> may be closed to prevent further infusion of resin. Rather than relying on visual identification, completion of resin infusion may be determined based on a predetermined resin infusion time period. At the completion of resin infusion, rather than closing a resin inlet valve, the oven temperature may be elevated to commence curing of the resin, therefore stopping further infusion.

The resin infused composite preform <NUM> may be cured by elevating the temperature of the oven to a temperature suitable for curing of the resin. For epoxy resins, curing temperatures of the order of <NUM> to <NUM> will be typical. Full vacuum is typically maintained on the first vacuum source <NUM> during the curing process, to ensure the resin infused composite preform <NUM> remains consolidated and to assist in curing of the resin.

Once the resin has cured, and the system cooled to room temperature, the various consumable layers, including the vacuum bagging film <NUM>, the layer <NUM> and various strips <NUM>, <NUM>, <NUM> of permeable flow media, and peel ply <NUM> are removed, along with the resin reservoir element <NUM>. The resin reservoir element <NUM> may be removed from the tool surface <NUM> and excess resin that has been collected and cured in the resin reservoir <NUM> may be removed, allowing the reuse of the resin reservoir element <NUM>. Alternatively, the resin reservoir element <NUM> may be discarded. Discarding of the resin reservoir element <NUM> will particularly be suitable where it is inexpensively formed from cutting a simple tubular section.

Vacuum bagging films typically exhibit some air permeability, particularly at elevated temperatures associated with resin infusion and/or resin cure. Accordingly, one potential deficiency of the single vacuum bag configuration of the resin infusion system <NUM> of the first embodiment is that, with vacuum applied during the curing process, air may permeate through the vacuum bagging film <NUM> and into the composite preform <NUM>, potentially resulting in porosity and resin starvation within the cured composite laminate. A double bag resin infusion system is thus envisaged in an effort to minimise or avoid such air permeation, by providing a second vacuum bagging film covering the first vacuum bagging film and applying vacuum pressure to the second vacuum bagging film during both the resin infusion and curing stages of operation.

<FIG> and <FIG> depict schematic cross-sectional views (corresponding to <FIG> and <FIG>) of such a double-bag configuration of the system <NUM> of the first embodiment, forming a system <NUM> according to a second embodiment. The system <NUM> of the second embodiment is substantially identical to the system <NUM> of the first embodiment, with the addition of a second vacuum bagging film <NUM> and associated breather layer <NUM>. Accordingly, features of the system <NUM> of the second embodiment that are identical to features of the system <NUM> of the first embodiment are provided with identical reference numerals and will not be further discussed.

In the system <NUM> of the second embodiment as depicted in <FIG> and <FIG>, the composite preform <NUM>, resin reservoir element <NUM> and associated consumable layers, such as the layer <NUM> and various strips <NUM>, <NUM>, <NUM> of permeable flow media, peel ply <NUM> and first vacuum bagging film <NUM> are first assembled in the same manner as described above in relation to the system <NUM> of the first embodiment. A breather layer <NUM>, typically being a highly permeable fabric formed of fibreglass, polyester or the like is then located over, and fully covering, the first vacuum bagging film <NUM>. A suitable breather layer is a breather cloth formed of a high film non-woven polyester material, such as AIRWEAVE® N10, available from Airtech International Inc. The breather layer <NUM> extends over a vacuum groove <NUM> that extends around the perimeter of the tool surface <NUM> and is connected to the first vacuum source <NUM> (or a separate third vacuum source) by way of a third vacuum pipe <NUM>. The second vacuum bagging film <NUM> is then located to cover the entire breather layer <NUM> and is sealed relative to the tool surface <NUM> by way of further strips <NUM> of sealing tape, forming a sealed cavity between the first and second vacuum bagging films <NUM>, <NUM>. The composite preform <NUM> is resin infused and subsequently cured using the same process as described above in relation to the system <NUM> of the first embodiment, with at least a partial vacuum being applied to the sealed cavity between the first and second vacuum bagging films <NUM>,<NUM> by the first vacuum source <NUM> (or separate third vacuum source) throughout resin infusion and curing. The second vacuum bagging film <NUM> and associated vacuum applied to the sealed cavity protects against any minor leaks associated with the first vacuum bag <NUM>, with the vacuum applied evacuating any air permeating through the second vacuum bagging film <NUM> toward the composite preform <NUM> through the breather layer <NUM>, rather than allowing it to permeate through to the composite preform <NUM>.

Referring to <FIG> of the accompanying drawings, a system <NUM> for resin infusing a composite preform <NUM> according to a third embodiment will now be described. The system <NUM> is of the same basic configuration and adopts the same principles as the system <NUM> according to the first embodiment, but is particularly suitable for the production of elongate composite articles having a concave section, such as spars and d-noses of wings, moveable trailing edge assemblies, moving leading edge assemblies, vertical and horizontal stabilizers and the like. In <FIG>, only the downstream portion of the system <NUM> is depicted, with the upstream portion, being of the same basic configuration as that of the system <NUM> of the first embodiment. Features of the system <NUM> of the third embodiment that are equivalent to those of the system <NUM> of the first embodiment are provided with like reference numerals, incremented by <NUM> in the accompanying drawings.

The composite preform <NUM>, which particularly represents a composite preform for a moveable trailing edge spar, has a longitudinally extending central web <NUM> and opposing flanges <NUM> extending along the opposing side edges <NUM> of the composite preform <NUM>. The composite preform <NUM>, which would typically be flexible when first laid up, has opposing edge portions each forming a flange <NUM> draping over the upper tool surface <NUM> of the tool <NUM> along the side wall <NUM> of a corresponding recess <NUM> extending along the side of a central planar portion <NUM> of the tool surface <NUM>. In the configuration of the system <NUM>, the resin reservoir element <NUM> is located downstream of the vacuum outlet <NUM> extending through the tool <NUM>. The portion of the resin flow path extending between the downstream edge <NUM> of the composite preform <NUM> and the reservoir inlet <NUM> is defined by a separate permeable resin flow control choke <NUM>, a laterally extending strip <NUM> of permeable flow media extending laterally across a downstream portion of the flow control choke <NUM> and a pair of longitudinally extending further strips <NUM> of permeable flow media communicating the strip <NUM> of permeable flow media with the reservoir inlet <NUM>, with the strips <NUM> extending beneath the first lower edge <NUM> of the channel section <NUM> of the resin reservoir element <NUM>.

The resin reservoir element <NUM> is provided with a single centrally located reservoir outlet <NUM> which communicates with the first vacuum source (not depicted) via a vacuum flow path including a further strip <NUM> of permeable flow media extending from the reservoir outlet <NUM>, and covering the vacuum outlet port <NUM>. Strips of sealing tape <NUM> are again used to seal the vacuum bagging film covering the composite preform <NUM> (and peel ply and layer of permeable flow media located on the same, but not specifically depicted in <FIG>) and resin reservoir element <NUM>. Further strips of sealing tape are also used, consistent with the manner described above in relation to the system <NUM> of the first embodiment, to isolate the vacuum flow path from the resin infusion chamber. The composite preform <NUM> is then resin infused in the same general manner as described above in relation to the system <NUM> of the first embodiment. In a modified form of the system <NUM> of the third embodiment, a further vacuum bagging film may be utilized below the composite preform <NUM>, between the composite preform <NUM> and the tool surface <NUM>, such that the composite preform <NUM> is located indirectly on the tool surface <NUM>.

A general method of resin infusing the composite preform as discussed above is depicted in general terms in the flow diagram of <FIG>. At block <NUM>, a tool having an upper tool surface is provided. A block <NUM>, a composite preform is located on the tool surface. At block <NUM>, a resin reservoir element is located on the tool surface on a downstream side of the composite preform. The resin reservoir element and tool surface define a resin reservoir, with the resin reservoir having a reservoir outlet and a reservoir inlet located between the tool surface and the reservoir outlet. Block <NUM> represents a vacuum bag being placed over the tool surface to cover the composite preform and the resin reservoir element. Block <NUM> represents the vacuum bagging film being sealed relative to the tool surface to define a sealed resin infusion chamber between the tool surface and vacuum bagging film, with the composite preform and resin reservoir element located in the resin infusion chamber. Block <NUM> represents provision of a resin supply. Block <NUM> represents provision of a resin flow path from the resin supply to the resin infusion chamber on an upstream side of the composite preform, through the composite preform and through the reservoir inlet to the resin reservoir. Block <NUM> represents application of at least partial vacuum pressure to the reservoir outlet to establish a pressure differential between the resin supply and the reservoir outlet to drive resin from the resin supply through the resin flow path, infusing the composite preform with resin and collecting excess resin in the resin reservoir.

In summary, block <NUM>: Provide a tool having an upper tool surface.

Block <NUM>: Locate a composite preform on the tool surface.

Block <NUM>: Locate a resin reservoir element on the tool surface on a downstream side of the composite preform to define a resin reservoir, with a reservoir outlet and a reservoir inlet located between the tool surface and the reservoir outlet.

Block <NUM>: Place a vacuum bagging film over the tool surface to cover the composite preform and the resin reservoir element.

Block <NUM>: Seal the vacuum bagging film relative to the tool surface to define a sealed resin infusion chamber between the tool surface and the vacuum bagging film, with the composite preform and resin reservoir element located in the resin infusion chamber.

Block <NUM>: Provide a resin flow path from the resin supply to the resin infusion chamber on an upstream side of the composite preform, through the composite preform and through the reservoir inlet to the resin reservoir.

Block <NUM>: Apply at least partial vacuum pressure to the reservoir outlet to establish a pressure differential between the resin supply and the reservoir outlet to drive resin from the resin supply through the resin flow path, infusing the composite preform with resin and collecting excess resin in the resin reservoir.

The disclosure includes a method of forming a composite article which involves resin infusing the composite preform <NUM> of claim <NUM> to form a resin infused composite preform and curing the resin infused composite preform, and optionally the method of forming the composite article may further comprise: removing the resin reservoir element <NUM> from the tool surface <NUM> following curing of the resin infused composite preform; and removing excess resin collected in the resin reservoir <NUM> from the resin reservoir element <NUM>.

Claim 1:
A method of resin infusing a composite preform (<NUM>), said method comprising:
locating a composite preform (<NUM>) on an upper tool surface (<NUM>) of a tool (<NUM>);
locating a resin reservoir element (<NUM>) on said tool surface (<NUM>) on a downstream side of said composite preform (<NUM>), said resin reservoir element (<NUM>) and said tool surface (<NUM>) defining a resin reservoir (<NUM>), said resin reservoir (<NUM>) having a reservoir outlet (<NUM>) and a reservoir inlet (<NUM>) located between said tool surface (<NUM>) and said reservoir outlet (<NUM>);
placing a vacuum bagging film (<NUM>) over said tool surface (<NUM>) to cover said composite preform (<NUM>) and said resin reservoir element (<NUM>);
sealing said vacuum bagging film (<NUM>) relative to said tool surface (<NUM>) to define a sealed resin infusion chamber (<NUM>) between said tool surface (<NUM>) and said vacuum bagging film (<NUM>), said composite preform (<NUM>) and said resin reservoir element (<NUM>) being located in said resin infusion chamber (<NUM>);
providing a resin supply (<NUM>);
providing a resin flow path (<NUM>) from said resin supply (<NUM>) to said resin infusion chamber (<NUM>) on an upstream side of said composite preform (<NUM>), through said composite preform (<NUM>) and through said reservoir inlet (<NUM>) to said resin reservoir (<NUM>);
applying at least partial vacuum pressure to said reservoir outlet (<NUM>) to establish a pressure differential between said resin supply (<NUM>) and said reservoir outlet (<NUM>) to drive resin from said resin supply (<NUM>) through said resin flow path (<NUM>), infusing said composite preform (<NUM>) with resin and collecting excess resin in said resin reservoir (<NUM>); and
locating a resin flow control choke in said resin flow path between said composite preform and said resin reservoir.