Patent Description:
An increasing number of composite materials are being used on aircraft. Composite materials typically include reinforcing fibers bound to a polymer resin matrix. The fibers may be unidirectional. Alternatively, the fibers may take the form of a woven cloth or fabric. The fibers and polymer resin are arranged and cured to form a composite structure. Some examples of composite materials that may be used in an aircraft include aircraft windows and door frames.

There are various challenges that exist when fabricating composite structures using conventional processes. For example, circular or elliptical composite components may require specific lay-up schemes to create lay-ups. The lay-up schemes are often controlled by the limitation of existing processes. Examples of these existing processes include fiber placement or fabric making machines. However, fiber placement or fabric making machines are typically tailored specifically for a particular configuration or final structure of the finished product. Current processes based on automated fiber placement or woven fabric are costly, time consuming, and may not be advantageous for components having tight radii.

Some composite components require a hole or aperture defined within the structure. For example, aircraft window frames define an aperture. It may be especially difficult and laborious to orient the reinforcing fibers for a composite component having an aperture. Additionally, when conventional manufacturing processes are used to fabricate a composite component having an aperture, relatively large amounts of material waste may be produced.

Thus, while current methods and systems for fabricating composite structures achieve their intended purpose, there is a need for a new and improved system and method of fabricating composite structures.

In accordance with its abstract, <CIT> states 'RPTextile reinforcing fiber structures (<NUM>) are laid on formers (<NUM>) and held in position using a binder. Each former has a negative or positive shape corresponding to a fiber preform section (<NUM>) to be produced. Textile reinforcing fiber structures (<NUM>) are laid on formers (<NUM>) and held in position using a binder. Each former has a negative or positive shape corresponding to a fiber preform section (<NUM>) to be produced. Preform sections are removed from their respective former, assembled and compacted to form a preform of the final product shape. A composite molded product is then created by impregnating the preform with a resin matrix. An Independent claim is made for the process equipment which includes a rotating former with a cylindrical or ring shaped holding surface (<NUM>) for forming the initial textile structure.

More specifically <CIT> states at paragraph [<NUM>] 'The apparatus schematically illustrated in FIGS. 1A and 1B includes a rotating carrier and reforming tool <NUM>, which comprises a cylindrical drum <NUM> and a bounding flange disc <NUM> secured to a side of the drum <NUM>. The diameter of the bounding flange disc <NUM> is larger and extends outwardly beyond the diameter of the drum <NUM>. Thus, the bounding flange disc <NUM> presents a radially extending annular flange-like receiving surface <NUM> for receiving a portion of a textile semi-finished article <NUM> thereon, while the drum <NUM> presents an outer cylindrical receiving surface <NUM> for another portion of the textile semi-finished article <NUM>.

In accordance with its abstract <CIT> states ' A textured tubular body for use in a tubular battery storage plate is produced by a braiding or weaving technique, and has a latticework of spaced apart reinforced tapes (<NUM>,<NUM>) which are interwoven to define interrupted rows of spaces (<NUM>) and control the porosity of the tubular body. A foraminous material (<NUM>,<NUM>), which retains active material of the battery plate, is arranged to close the spaces (<NUM>) in the latticework. The tapes (<NUM>,<NUM>) are braided along oppositely directed helical paths to produce a seamless latticework in which the rows of spaces (<NUM>) occur angularly with respect to one another. Simultaneously a network of foraminous fibers (<NUM>,<NUM>) is braided and interwoven with the latticework. The foraminous fibers (<NUM>,<NUM>) are confined between edges of the tapes (<NUM>,<NUM>) to provide a desired porosity in the textured material.

According to several aspects, a composite structure is disclosed. The composite structure includes a formed winding of tubular braiding.

In another aspect of the present disclosure, a composite structure including a biaxial braiding that is formed into a winding is disclosed.

According to several aspects, a composite structure including a tubular braiding that is biaxially braided is disclosed.

In another aspect of the present disclosure, a composite laminate structure including a plurality of plies is disclosed. The composite structure includes biaxially braided fibers oriented in the same direction for each of the plurality of plies.

In yet another aspect of the present disclosure, a braiding machine is disclosed and includes a mandrel, a braiding mechanism having spools each moveable relative to the mandrel, a unidirectional tape wound around each of the spools, a guide ring, and a control module. The guide ring directs the unidirectional tape wound around a corresponding spool onto the mandrel. The control module is in electronic communication with the braiding mechanism. The control module executes instructions to guide movement of the plurality of spools to place the unidirectional tape onto the mandrel to create a tubular braiding.

In still another aspect of the present disclosure, an apparatus for fabricating a composite structure of wound tubular braiding is disclosed. The apparatus includes a tool defining an outer surface, a device to wind the tubular braiding around the outer surface of the tool to create a composite preform, a forming device to consolidate the composite preform, and a control module. The control module is in electronic communication with the device and the forming device. The control module executes instructions to guide the device to wind the tubular braiding around the outer surface of the tool and operate the forming device to consolidate the composite preform.

According to several aspects, a method of forming a composite structure is disclosed. The method includes forming a wound tubular braiding into the composite structure.

In still another aspect of the disclosure, a method of fabricating a composite preform is disclosed. The method includes winding a tubular braiding of unidirectional fibers while allowing the unidirectional fibers shift to relative to one another without bending.

In another aspect of the disclosure, a method of forming a tubular braiding is disclosed. The method includes braiding unidirectional tape into the tubular braiding.

In another aspect of the disclosure, a wound tubular braiding for a composite structure is disclosed. The wound tubular braiding includes a tubular braiding wound into a helical shape.

The features, functions, and advantages that have been discussed may be achieved by the present disclosure, further details of which can be seen with reference to the following description and drawings.

A composite structure constructed of a formed winding of tubular braiding is disclosed. The tubular braiding is constructed of a unidirectional tape. A braiding machine for fabricating the tubular braid is also disclosed. The braiding machine includes a braiding mechanism and a mandrel. A plurality of spools having unidirectional tape wound around each spool are mounted to the braiding mechanism. The braiding mechanism controls placement of the unidirectional tape from the spools and onto the mandrel to create the tubular braiding. The tubular braiding may have a biaxial braid or a triaxial braid.

An apparatus for fabricating the composite structure by winding the tubular braiding around a tool is also disclosed. The braiding can be first removed from the mandrel and wound around an outer surface of the tool to create a wound tubular braiding. The mandrel may remain with, and form part of, the wound tubular braiding. The tubular braiding can be slit to remove the mandrel. The unidirectional tape is not constricted as the tubular braiding is wound around the tool. In other words, the unidirectional tape slips or shears relative to one another as the tubular braiding is wound around the tool. This relative slippage or shearing of the unidirectional tape or unidirectional tow permits the construction of structures without wrinkling yet having fiber direction orientated advantageously relative to the final structure. The wound tubular braiding is then removed from the tool and is heated and compacted flat by a forming machine to create the composite structure. Once again, the unidirectional tap is not constricted and slip or shear relative to one another as the tubular braiding is compacted flat.

Allowing the unidirectional fibers to slip or shear relative to one another during winding and consolidating the composite preform results in a composite structure having more fibers orientated advantageously relative to the structure per ply of laminate being created. Moreover, the resulting composite structure also requires fewer plies of laminate to achieve strength goals since more fibers are orientated advantageously relative to structure per ply of laminate makes the structure more efficient This in turn results in weight reduction of the component. The disclosed process of creating the composite structure is rapid when compared to conventional lay-up processes, which in turn enables higher production rates. Furthermore, the disclosed process for creating the composite also results in reduced waste and labor intensive post-processing machining when compared to conventional processes.

Referring to <FIG>, a schematic diagram of a system <NUM> for constructing composite structures is shown. The system <NUM> generally includes tooling <NUM> and work product <NUM> upon which the tooling <NUM> interacts. The tooling <NUM> includes a braiding machine <NUM>, a winding tool <NUM>, and a forming machine <NUM>. The work product <NUM> includes a tubular braiding <NUM>, a wound tubular braiding <NUM>, and a composite structure <NUM>. The wound tubular braiding <NUM> may also be referred to as a winding of tubular braiding. The tubular braiding <NUM> is formed by the braiding machine <NUM>. The wound tubular braiding <NUM> is formed by the winding tool <NUM> from the tubular braiding <NUM>. The composite structure <NUM> is formed by the forming machine <NUM> from the wound tubular braiding <NUM>. The composite structure <NUM> is any frame that surrounds and provides support to an aperture that requires a specific fiber orientation and lay up to meet design requirements. For example, the composite structure <NUM> may be a window frame for an aircraft, a door frame for an aircraft, etc. The tooling <NUM> may include other machines, such as molding or post-processing machines, cutting devices, etc., without departing from the scope of the present disclosure. Likewise, the work product <NUM> may include additional variations of the tubular braiding <NUM>, wound tubular braiding <NUM>, and composite structure <NUM>. The system <NUM> may be employed in the context of aircraft manufacturing and service, as will be described below. For example, the system <NUM> may be used in component and subassembly manufacturing of an aircraft including an airframe and interior, system integration of the aircraft, and routine maintenance and service of the aircraft.

With reference to <FIG>, a schematic side view of the braiding machine <NUM> is illustrated. The braiding machine <NUM> includes a braiding mechanism <NUM> and a mandrel <NUM>. The braiding mechanism <NUM> is configured to braid a unidirectional tape <NUM> onto the mandrel <NUM>, as will be described below. The mandrel <NUM> is supported and advanced by a holder <NUM> along a center axis "A" of the braiding mechanism <NUM>.

With reference to <FIG> and continued reference to <FIG>, an illustration of the braiding machine <NUM> viewed in the direction of section line <NUM>-<NUM> in <FIG> is shown. The braiding mechanism <NUM> includes a carrier <NUM> supported by a base plate <NUM>. The carrier <NUM> is ringshaped and defines an aperture 34A. The mandrel <NUM> passes through the aperture 34A during braiding along center axis "A". A number of spools <NUM> are mounted to the carrier <NUM>. The spools <NUM> are each moveable relative to the mandrel <NUM> annularly about the center axis of the carrier <NUM>. The unidirectional tape <NUM> is wound around each of the spools <NUM>. While in <FIG> five spools <NUM> are schematically shown and in <FIG> numerous spools <NUM> are illustrated, it should be appreciated that any number of spools <NUM> may be used depending on the desired properties of the tubular braiding <NUM>. For example, the braiding mechanism <NUM> can include as few as forty spools <NUM> or as many as two hundred spools <NUM>. The spools <NUM> generally include warp spools 38A and weft spools 38B. The warp spools 38A are moved in a clockwise direction C (shown in <FIG>) by the carrier <NUM> and the weft spools 38B in a counter-clockwise direction CC (shown in <FIG>) by the carrier <NUM>. The warp spools 38A and the weft spools 38B are preferably moved at the same speed.

The braiding mechanism <NUM> further includes a guide ring <NUM> positioned around the mandrel <NUM>. The guide ring <NUM> directs the unidirectional tape <NUM> wound around a corresponding spool <NUM> onto the mandrel <NUM>. Specifically, the unidirectional tape <NUM> is directed from a corresponding spool <NUM> onto the mandrel <NUM> through a convergence zone <NUM>. The point where the unidirectional tape <NUM> first comes into contact with the mandrel <NUM> is denoted as a fell point <NUM>.

The mandrel <NUM> acts as a substrate on which the unidirectional tape <NUM> is braided by the braiding mechanism <NUM> to form the tubular braiding <NUM>. The mandrel <NUM> may have various shapes but is preferably an elongated cylinder. The diameter of the mandrel <NUM> can be <NUM> (<NUM> inches). However, it should be appreciated that the mandrel <NUM> may have other diameters depending on the design requirements of the composite structure <NUM>. The size or volume of the mandrel <NUM> may be controlled. For example, the mandrel <NUM> is an inflatable tube, such as a silicon bladder. However, the mandrel <NUM> may have a fixed size or volume. For example, the mandrel <NUM> is constructed of a solid semi-rigid material such as, but not limited to, ethylene propylene diene monomer (EPDM), rubber, silicone, neoprene, or natural rubber. The mandrel <NUM> can be constructed of a thin film polymer compatible with the composition of the unidirectional tape <NUM>.

An inflation mechanism <NUM> is connected to the mandrel <NUM> by a supply line <NUM>. The inflation mechanism <NUM> provides pressurized air or another gas or liquid to the mandrel <NUM>. The inflation mechanism <NUM> cycles the mandrel <NUM> between a deflated state and an inflated state.

Turning briefly to <FIG>, an enlarged view of the unidirectional tape <NUM>, indicated by section view <NUM>-<NUM> in <FIG>, is shown. The unidirectional tape <NUM> comprises unidirectional fibers <NUM> in a continuous strip held together by thermal or adhesive bonding. The unidirectional fibers <NUM> are parallel with one another. The unidirectional fibers <NUM> may be pre-impregnated with a resin. The resin can be a thermoplastic such as, for example polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), etc. However, the resin can be a thermoset resin such as, for example, epoxy, cyanate ester, etc. The unidirectional fibers <NUM> may be held together by relatively fine holding threads (not shown). The holding threads are not woven with the unidirectional fibers <NUM>. Instead, the holding threads are deposited on the top and bottom sides of the unidirectional tape <NUM>. The unidirectional tape <NUM> can be comprised of a unidirectional tow. A unidirectional tow includes unidirectional fibers that are held together by stitching threads crossing over several carbon tows. The unidirectional tape <NUM> can be constructed of a slit-tape thermoplastic, a thermoset tape that is substantially tack-free at room temperature, a substantially tack-free thermoset prepreg, or a low tack thermoset prepreg.

Returning to <FIG> and <FIG>, the operation of the braiding machine <NUM> is controlled by a control module <NUM> (shown in <FIG>). The control module <NUM> is in communication with the braiding mechanism <NUM>, the holder <NUM>, and the inflation mechanism <NUM>. The control module <NUM> may refer to, or be part of an electronic circuit, a combinational logic circuit, a field programmable gate array (FPGA), a processor (shared, dedicated, or group) that executes code, or a combination of some or all of the above, such as in a system-on-chip. Additionally, the control module <NUM> may be microprocessor-based such as a computer having a at least one processor, memory (RAM and/or ROM), and associated input and output buses. The processor may operate under the control of an operating system that resides in memory. The operating system may manage computer resources so that computer program code embodied as one or more computer software applications, such as an application residing in memory, may have instructions executed by the processor. The processor may execute the application directly, in which case the operating system may be omitted.

The control module <NUM> controls movement of the mandrel <NUM> via the holder <NUM> and movement of the spools <NUM> to braid the unidirectional tape <NUM> onto the mandrel <NUM> to form the tubular braiding <NUM>. For example, the control module <NUM> executes instructions to inflate the mandrel <NUM> to the inflated state by commanding the inflation mechanism <NUM> to provide pressurized air to the mandrel <NUM>. The control module <NUM> executes instructions to guide movement of the mandrel <NUM> in an axial direction 'A' (shown in <FIG>) through the carrier <NUM>. As the mandrel <NUM> moves through the carrier <NUM>, the control module <NUM> executes instructions to move the warp spools 38A in the clockwise C direction and the weft spools 38B in the counter clockwise CC direction around the mandrel <NUM>. The unidirectional tape <NUM> is pulled from a corresponding spool <NUM>. The unidirectional tape <NUM> from the warp spools 38A and the weft spools 38B interlock or weave together with one another to create the tubular braiding <NUM> on the mandrel <NUM>. The control module <NUM> can receive an indication that the unidirectional tape <NUM> is wound around the mandrel <NUM>. Specifically, the indication means that the braiding machine <NUM> has finished placing the unidirectional tape <NUM> onto the mandrel <NUM> to create the tubular braiding <NUM>. For example, the indication may be a manual input from a user. Alternatively, a sensor may provide an indication that the braiding machine <NUM> has finished creating the tubular braiding <NUM>. In response to receiving the indication, the control module <NUM> instructs the inflation mechanism <NUM> to release air to deflate the mandrel <NUM>.

Where the mandrel <NUM> is not inflatable, the tubular braiding <NUM> can be slit to remove the mandrel <NUM>. For example, a cutting machine (not shown) or worker may be used to slit the tubular braiding <NUM> along an entire length thereof, thus allowing the mandrel <NUM> to be removed. An example of a slit <NUM> is shown by dashed line in <FIG>. Alternatively, where the mandrel <NUM> is comprised of the thin film polymer compatible with the composition of the unidirectional tape <NUM>, the mandrel <NUM> remains with, and forms part of, the tubular braiding <NUM>.

The control module <NUM> can execute instructions to provide air via the inflation mechanism <NUM> to inflate the mandrel <NUM> only partially. Once the control module <NUM> receives an indication that the unidirectional tape <NUM> is wound around the mandrel <NUM>, the control module <NUM> then executes instructions to provide air by the inflation mechanism <NUM> to further inflate the mandrel <NUM>, which in turn places the unidirectional fibers <NUM> into tension. Alternatively, the mandrel <NUM> may remain partially inflated during the braiding. Fully inflating the mandrel <NUM> allows for near-zero fiber angle lay-up and avoids any collapse or volume shrinkage of the mandrel <NUM> where the braid of unidirectional tape <NUM> is tight. Partially inflating the mandrel <NUM> to a point where the mandrel is geometrically stable allows for a relatively flexible or loose braid of unidirectional tape <NUM>. This, in turn, allows the unidirectional tape <NUM> to slip or shear during winding and forming, as described below. In both cases, controlling the size or volume of the mandrel <NUM> provides the ability to customize a geometry of the tubular braiding <NUM> that is braided onto the mandrel <NUM>.

<FIG> shows an enlarged portion of the tubular braiding <NUM> viewed in the direction of arrows <NUM>-<NUM> in <FIG>. In the example provided, the tubular braiding <NUM> includes a biaxial braid <NUM>. In the biaxial braid <NUM>, a matrix of parallel unidirectional tape 32A are interwoven or braided into an matrix of orthogonal parallel unidirectional tape 32B. The parallel unidirectional tape 32A is disposed at a bias angle α to the orthogonal parallel unidirectional tape 32B. The bias angle α is determined based on the specific application, however steeper braid angles result in increased flexibility. However, angle α may change when the unidirectional tape is wound or formed, as described below.

Returning back to <FIG>, the braiding machine <NUM> may also be configured to form a tubular braiding <NUM> having a triaxial braid. To form a tubular braiding <NUM> with a triaxial braid, the unidirectional tape <NUM> is inserted along a length "L" of the mandrel <NUM> from fixed spools 32C (only one of which is shown). The fixed spools 32C do not rotate along the frame <NUM>. It should be appreciated that any number of fixed spools 32C may be employed.

<FIG> shows an enlarged portion of the tubular braiding <NUM> with a triaxial braid <NUM> viewed in the direction of arrows <NUM>-<NUM> in <FIG>. The triaxial braid <NUM> is similar to the biaxial braid <NUM> (<FIG>), however, an additional matrix of parallel unidirectional tape 32C, extending the axial length of the tubular braiding <NUM> parallel to the center axis "A" (<FIG>), is interwoven into the parallel unidirectional tape 32A and orthogonal parallel unidirectional tape 32B. The unidirectional tape 32C is supplied from the fixed spools 32C. Again, the bias angle α may change when the unidirectional tape is wound or formed, as described below. The triaxial braid <NUM> may provide enhanced structural strength in the longitudinal direction of the tubular braiding <NUM>.

With reference to <FIG>, and continued reference to <FIG>, a flow diagram is shown illustrating a method <NUM> of forming the tubular braiding <NUM> where a size or volume of the mandrel <NUM> is controlled. The method <NUM> begins at block <NUM>. In block <NUM>, the control module <NUM> controls the size or volume of the mandrel <NUM> prior to braiding. In one example, the mandrel <NUM> is inflatable by the inflation mechanism <NUM>. Thus, the control module <NUM> instructs the inflation mechanism <NUM> to provide air to inflate the mandrel <NUM>. The mandrel <NUM> can be inflated fully or partially inflated. The method <NUM> then proceeds to block <NUM>.

In block <NUM>, the method <NUM> includes braiding the unidirectional tape <NUM> around the mandrel <NUM> to form the tubular braiding <NUM>. For example, the control module <NUM> commands the mandrel <NUM> to move axially in the direction "A" while commanding the spools <NUM> to rotate, thus forming a braid of unidirectional tape <NUM> on the mandrel <NUM>, as described above. Depending on the configuration of the braiding mechanism <NUM>, one of a biaxial braid <NUM> (<FIG>) or a triaxial braid <NUM> (<FIG>) is formed on the mandrel <NUM> and the method <NUM> proceeds to block <NUM> or block <NUM>.

In block <NUM>, the braiding machine <NUM> braids the tubular braiding <NUM> with the biaxial braid <NUM> (<FIG>). In block <NUM>, the braiding machine <NUM> braids the tubular braiding <NUM> with the triaxial braid <NUM> (<FIG>). In either case, the method <NUM> proceeds to block <NUM>.

In block <NUM>, the control module <NUM> controls the size or volume of the mandrel <NUM> after the braiding is complete. For example, the control module <NUM> instructs the inflation mechanism <NUM> to deflate the mandrel <NUM>, thus allowing the tubular braiding <NUM> to be easily removed from the mandrel <NUM>.

With reference to <FIG>, and continued reference to <FIG>, a flow diagram is shown illustrating a method <NUM> of forming the tubular braiding <NUM> where the mandrel <NUM> is not inflatable. The method <NUM> begins at block <NUM>. In block <NUM>, the method <NUM> includes placing the unidirectional tape <NUM> on the mandrel <NUM>. For example, a combination of unidirectional tape 32A, 32B, or 32C may be placed on the mandrel <NUM>. The method <NUM> then proceeds to block <NUM>.

At block <NUM> the control module <NUM> commands the mandrel <NUM> to move axially along the center axis "A" (<FIG>). At block <NUM>, the control module <NUM> commands the warp spools 38A and the weft spools 38B to counter rotate about the center axis "A" as the mandrel <NUM> moves along the center axis "A". Depending on which type of braid <NUM>, <NUM> (<FIG>, <FIG>) is to be produced, the method <NUM> proceeds to either block <NUM> or block <NUM>.

At block <NUM> the unidirectional tape 32A, 32B are interlaced together to form the biaxial braid <NUM> (<FIG>). For example, as the mandrel <NUM> moves along the center axis "A", the warp spools 38A and the weft spools 38B counter-rotate. Movement of the mandrel <NUM> draws out the unidirectional tape <NUM> disposed on the warp spools 38A and the weft spools 38B. The counter-rotation of the warp spools 38A and the weft spools 38B interlaces the unidirectional tape 32A from the warp spools 38A with the unidirectional tape 32B from the weft spools 38B as the mandrel <NUM> moves along the center axis "A" (<FIG>). At block <NUM> the tubular braiding <NUM> has been formed with a biaxial braid <NUM> (<FIG>).

At block <NUM> the unidirectional tape 32A, 32B, and 32C are interlaced together to form the triaxial braid <NUM> (<FIG>). For example, as the mandrel <NUM> moves along the center axis "A", the warp spools 38A and the weft spools 38B counter-rotate. Movement of the mandrel <NUM> draws out the unidirectional tape 32A disposed on the warp spools 38A, the unidirectional tape 32B disposed on the weft spools 32B, and the unidirectional tape 32C disposed on the fixed spools 38C. The counter-rotation of the warp spools 38A and the weft spools 38B interlaces the unidirectional tape 32A from the warp spools 38A with the unidirectional tape 32B from the weft spools 38B and with the unidirectional tape 32C from the fixed spools 38C as the mandrel <NUM> moves along the center axis "A" (<FIG>). At block <NUM> the tubular braiding <NUM> has been formed with a triaxial braid <NUM> (<FIG>).

In either case, the method <NUM> ends when the tubular braiding <NUM> has been formed. Where the mandrel <NUM> is removable, the method <NUM> may also include slitting the tubular braiding <NUM> along an entire length thereof to assist in removing the mandrel <NUM>. Where the mandrel <NUM> is formed of the thin film polymer compatible with the composition of the unidirectional tape <NUM>, the mandrel <NUM> remains with, and forms part of, the tubular braiding <NUM>.

Turning to <FIG>, the winding tool <NUM> will now be described. The winding tool <NUM> generally includes a body portion <NUM> that extends vertically It should be appreciated that the body portion <NUM> may extend horizontally or at an angle. The body portion <NUM> has an outer surface <NUM>. The outer surface <NUM> generally conforms to a shape of the composite structure <NUM>. Thus, a cross-sectional shape of the body portion <NUM> varies depending on the final shape of the composite structure <NUM>. In the example provided, the body portion <NUM> has a rectangular cross-section with rounded corners <NUM>. However, as shown in <FIG>, the body portion <NUM> may have a circular cross-section. Alternatively, as shown in <FIG>, the body portion <NUM> may have an elliptical or oval cross-section. It should be appreciated that the body portion <NUM> may have additional cross-sections without departing from the scope of the present disclosure.

With reference to <FIG>, to form the wound tubular braiding <NUM>, the tubular braiding <NUM> is wound around the outer surface <NUM> of the winding tool <NUM>. The tubular braiding <NUM> may be wound around the winding tool <NUM> manually or in an automated process using a device <NUM>, such as a robotic arm or manipulator, etc. The wound tubular braiding <NUM> is comprised of stacked turns <NUM> of the tubular braiding <NUM>. While in the example provided five stacked turns <NUM> are shown, it should be appreciated that the tubular braiding <NUM> may be wound around the winding tool <NUM> any number of times producing any number of stacked turns <NUM>. It should be appreciated that the number of stacked turns <NUM> is dependent upon the number of plies desired in the composite structure <NUM> and the thickness of the composite structure <NUM>. Where the tubular braiding <NUM> has the triaxial braid <NUM>, the unidirectional tape 32C (<FIG>) is orientated roughly parallel to the outer surface <NUM> of the winding tool <NUM> when the tubular braiding <NUM> is wound around the winding tool <NUM>. Thus, the unidirectional tape 32C (<FIG>) is disposed roughly parallel to an aperture and or an outer perimeter of the composite structure <NUM>.

Once the wound tubular braiding <NUM> is formed, the wound tubular braiding <NUM> is separated from the winding tool <NUM>, as shown in <FIG>. The wound tubular braiding <NUM> may be separated from the winding tool <NUM> manually or in an automated process using a robotic arm or manipulator (not shown), etc. The wound tubular braiding <NUM> has a first free end 24A and a second free end 24B. As seen in <FIG>, the wound tubular braiding <NUM> has a helical or spiral shape and is formed of a single length of tubular braiding <NUM>. The wound tubular braiding <NUM> is hollow and defines a central bore 24C that extends throughout the wound tubular braiding <NUM>. When separated from the winding tool <NUM>, the wound tubular braiding <NUM> has sufficient strength to maintain the overall shape that was provided by the winding tool <NUM>. To form the composite structure <NUM>, the wound tubular braiding <NUM> is placed in the forming machine <NUM>, as will be described below.

<FIG> shows a front perspective view of the forming machine <NUM> in an open position. The forming machine <NUM> includes an upper die plate <NUM> and a lower die plate <NUM>. In the example provided, the upper die plate <NUM> may be lowered on support members <NUM> via an electric motor <NUM> to mate with the lower die plate <NUM> in a closed position. Alternatively, the upper die plate <NUM> and the lower die plate <NUM> may be hinged together (not shown). The lower die plate <NUM> includes a lower mold surface <NUM> and a forming mandrel <NUM> extending from the lower mold surface <NUM>. The forming mandrel <NUM> is substantially the same size the cross section of the winding tool <NUM>. A heating element <NUM> is disposed within the lower die plate <NUM>. The heating element <NUM> is configured to heat the lower mold surface <NUM>. In the example provided, the heating element <NUM> includes electrical wires that heat the lower mold surface <NUM> via resistance heating. Alternatively, the heating element <NUM> may include hot oil pumped through tubes (not shown), inductive heaters, external heaters, etc. The upper die plate <NUM> and/or the forming mandrel <NUM> may also include a heating element (not shown) without departing from the scope of the present disclosure.

<FIG> shows a cross-section of the forming machine <NUM> in the closed position with the upper die plate <NUM> mated with the lower die plate <NUM>. The upper die plate <NUM> includes an upper mold surface <NUM>. An outer mold surface <NUM> extends down from the upper mold surface <NUM>. A recess <NUM> is formed in the upper mold surface <NUM>. When in the closed position, the forming mandrel <NUM> of the lower die plate <NUM> is mated within the recess <NUM> of the upper die plate <NUM>. Additionally, the lower mold surface <NUM>, the forming mandrel <NUM>, the upper mold surface <NUM>, and the outer mold surface <NUM> cooperate to define a mold cavity <NUM> between the upper die plate <NUM> and the lower die plate <NUM>. The mold cavity <NUM> surrounds the forming mandrel <NUM>.

The forming machine <NUM> can further include a vacuum source <NUM> that communicates with a vacuum port <NUM>. The vacuum port <NUM> is disposed in the lower mold surface <NUM> and communicates with the mold cavity <NUM>. The vacuum source <NUM> generates a vacuum in the mold cavity <NUM> to removes excess air, gases and voids from wound tubular braiding <NUM> during forming. The vacuum port <NUM> may alternatively, or in addition, be disposed in the upper mold surface <NUM>.

The forming machine <NUM> further includes a controller <NUM> in communication with the electric motor <NUM>, the heating element <NUM>, and the vacuum source <NUM>. The controller <NUM> may also be in communication with the device <NUM> used to wind the tubular braiding <NUM> around the winding tool <NUM> (see <FIG>). The controller <NUM> may refer to, or be part of an electronic circuit, a combinational logic circuit, a field programmable gate array (FPGA), a processor (shared, dedicated, or group) that executes code, or a combination of some or all of the above, such as in a system-on-chip. Additionally, the controller <NUM> may be microprocessor-based such as a computer having a at least one processor, memory (RAM and/or ROM), and associated input and output buses. The processor may operate under the control of an operating system that resides in memory. The operating system may manage computer resources so that computer program code embodied as one or more computer software applications, such as an application residing in memory, may have instructions executed by the processor. The processor may execute the application directly, in which case the operating system may be omitted.

The controller <NUM> controls movement of the upper die plate <NUM> and the lower die plate <NUM> via the electric motor <NUM>. The controller <NUM> also controls the temperature that is applied to the mold cavity <NUM> during forming of the wound tubular braiding <NUM> into the composite structure <NUM> via the heating element <NUM>. In one example, the controller <NUM> controls the temperature in the mold cavity <NUM> based on the type of resin used in the unidirectional tape <NUM> (<FIG>) that makes up the wound tubular braiding <NUM>. The thermoplastic resin can include a resin melt temperature that ranges from about <NUM> to over <NUM>, and a thermoset resin includes a resin melt temperature of about <NUM>. As used herein, the term "about" is known to those skilled in the art. Alternatively, the term "about" means +/- <NUM>. The controller <NUM> also controls the rate at which the mold cavity <NUM> is cooled to ensure cross-linking of the thermoset polymer in the unidirectional tape <NUM>. The controller <NUM> also controls applying a vacuum to the mold cavity <NUM> via the vacuum source <NUM>. As noted above, the vacuum removes excess air, gas, volatiles, and voids from the wound tubular braiding <NUM> in the mold cavity <NUM>. The controller <NUM> may also control resin infusion (not shown) of the wound tubular braiding <NUM> during forming. Resin infusion may be desirable where the unidirectional tape <NUM> employs a thermoset resin and where the unidirectional fibers <NUM> are tacked together with a binder into tows or tapes. The tacking provides enough binder to hold non-impregnated fibers together in tows of tape. The resin infusion impregnates the unidirectional fibers <NUM> with the resin.

With reference to <FIG> and <FIG>, the forming machine <NUM> is shown with the wound tubular braiding <NUM> disposed therein prior to forming. The wound tubular braiding <NUM> is disposed on the lower mold surface <NUM> and around the forming mandrel <NUM>. Thus, the wound tubular braiding <NUM> maintains the helical or spiral winding when disposed within the forming machine <NUM>.

<FIG> shows the forming machine <NUM> in the closed position with the wound tubular braiding <NUM> disposed therein. To form the composite structure <NUM>, the wound tubular braiding <NUM> is consolidated, i.e. compressed, by the upper die plate <NUM> and lower die plate <NUM> within the mold cavity <NUM>. For example, the controller <NUM> executes instructions to actuate the upper die plate <NUM> and the lower die plate <NUM> towards one another via the electric motor <NUM> until the upper die plate <NUM> is pressed against the lower die plate <NUM>. Pressing the upper die plate <NUM> against the lower die plate <NUM> consolidates the wound tubular braiding <NUM>. Next, the controller <NUM> applies heat to the wound tubular braiding <NUM> via the heating element <NUM>. As noted above, the temperature that is set, as well as the heating time and cooling time, is determined based on factors related to the material of the resin used in the wound tubular braiding <NUM>. In one example, the temperature is from about <NUM> to over <NUM> and in another example the temperature is set to about <NUM>. Either before or during heating, the controller <NUM> applies a vacuum to the mold cavity <NUM> via the vacuum source <NUM> to remove excess air, gas, volatiles, and voids from the wound tubular braiding <NUM> during consolidation and/or heating. Once consolidation, heating, and cool off has been accomplished, the controller <NUM> commands the electric motor <NUM> to open the forming machine <NUM> and the composite structure <NUM> is removed. The composite structure <NUM> may be removed manually or via a robotic arm or manipulator (not shown).

The composite structure <NUM> can be s over-molded to create additional features such as, for example, connectors or ribs (not shown). The composite structure <NUM> may also be trimmed in order to achieve a final profile.

<FIG> shows an example of the composite structure <NUM> formed using the braiding machine <NUM>, winding tool <NUM>, and forming machine <NUM> described above. The composite structure <NUM> includes a frame portion <NUM> that defines an aperture <NUM>. In the example provided the composite structure <NUM> is illustrated as a window frame for an aircraft. However, it is to be appreciated that the composite structure <NUM> may be any component that defines an aperture, and especially any component that also includes tight corners or radiuses. For example, the composite structure <NUM> may be a door frame or any other type of access frame. Referring back to <FIG>, the lower mold surface <NUM>, the upper mold surface <NUM>, and the forming mandrel <NUM> cooperate to define the shape of the frame portion <NUM>. In particular, the shape of the aperture <NUM> corresponds to the shape of the forming mandrel <NUM>, which in turn corresponds to the shape of the winding tool <NUM> (<FIG>). Thus, the body portion <NUM> of the winding tool <NUM> has roughly the shape of the aperture <NUM> and the outer edges of the wound tubular braiding <NUM> (<FIG>) form the outer perimeter of the composite structure <NUM>. Where the tubular braiding <NUM> has the triaxial braid <NUM>, the unidirectional tape 32C (<FIG>) is disposed roughly parallel to a perimeter of the aperture <NUM>. Returning to <FIG>, during forming in the forming machine <NUM>, the tubular braiding <NUM> (<FIG> and <FIG>) of the wound tubular braiding <NUM> is compacted flat when consolidated. In other words, the composite structure <NUM> has a solid cross-section.

<FIG> shows an enlarged, cross-section of the composite structure <NUM> viewed in the direction of section line <NUM>-<NUM> in <FIG>. The composite structure <NUM> has a composite laminate structure <NUM> that includes a plurality of plies <NUM>. Each of the plurality of plies <NUM> corresponds to a stacked turn <NUM> (<FIG>) of the wound tubular braiding <NUM>. Thus, each of the plurality of plies <NUM> include either a flattened biaxial braid <NUM> (<FIG>) or a flattened triaxial braid <NUM> (<FIG>). During consolidation and heating, the resin of the unidirectional tape <NUM> (<FIG> and <FIG>) forms a polymer matrix such that the plurality of plies <NUM> are defined by orientation of the unidirectional fibers <NUM> (<FIG>) that forms the unidirectional tape <NUM>. For each of the plurality of plies <NUM>, either the biaxial braid <NUM> or the triaxial braid <NUM> are oriented to form a hoop type configuration with a large volume of the unidirectional fibers <NUM> in the desire direction, thus increasing the efficiency of the composite structure <NUM>. In other words, the unidirectional fibers <NUM> (<FIG>) are oriented in the same direction for each of the plurality of plies <NUM> at any given cross section. The composite laminate structure <NUM> includes a predefined fiber to volume ratio, which may also be referred to as a fiber volume ratio. The fiber volume ratio represents the percentage of unidirectional fibers <NUM> in the composite laminate structure <NUM>. Mechanical properties of a composite structure such as, but not limited to, tensile strength depend upon the fiber to volume ratio. Thus, the fiber to volume ratio of the composite laminate structure <NUM> is determined based on a specific application or requirements.

It is to be appreciated that the forming machine <NUM> consolidates the wound tubular braiding <NUM> into a near net shape. As a result, the composite structure <NUM> requires less trimming to create a final profile when compared to conventional processes. Furthermore, the extensive post-processing and machining that is typically required to fabricate a composite structure is no longer needed.

Turning now to <FIG>, an exemplary process flow diagram illustrates a method <NUM> for fabricating the composite structure <NUM> using the system <NUM> described above in <FIG>. The method <NUM> beings at block <NUM>. In block <NUM>, the method <NUM> includes placing the unidirectional tape <NUM> on the mandrel <NUM>. For example, a combination of unidirectional tape 32A, 32B, or 32C may be placed on the mandrel <NUM>. The method <NUM> then proceeds to block <NUM>.

At block <NUM> the unidirectional tape 32A, 32B, and 32C are interlaced together to form the triaxial braid <NUM> (<FIG>). For example, as the mandrel <NUM> moves along the center axis "A", the warp spools 38A and the weft spools 38B counter-rotate. Movement of the mandrel <NUM> draws out the unidirectional tape 32A disposed on the warp spools 38A, the unidirectional tape 32B disposed on the weft spools 32B, and the unidirectional tape 32C disposed on the fixed spools 38C. The counter-rotation of the warp spools 38A and the weft spools 38B interlaces the unidirectional tape 32A from the warp spools 38A with the unidirectional tape 32B from the weft spools 38B and with the unidirectional tape 32C from the fixed spools 38C as the mandrel <NUM> moves along the center axis "A" (<FIG>). At block <NUM> the tubular braiding <NUM> has been formed with a triaxial braid <NUM> (<FIG>). Depending on the configuration of the mandrel <NUM> as noted above, the mandrel <NUM> may be separated from the tubular braiding <NUM> or left in the tubular braiding <NUM>. From block <NUM> or block <NUM>, the method <NUM> proceeds to block <NUM>.

Block <NUM> includes winding the tubular braiding <NUM> around the winding tool <NUM>. The winding of the tubular braiding <NUM> forms the wound tubular braiding <NUM> (<FIG>). As noted above, the winding may be done manually or via an automated process using the device <NUM>. The method <NUM> then proceeds to block <NUM>.

Block <NUM> includes forming the wound tubular braiding <NUM> into the composite structure <NUM>. For example, the wound tubular braiding <NUM> may be placed into the forming machine <NUM> (<FIG>). The controller <NUM> then consolidates, i.e. flattens, the wound tubular braiding <NUM> to form the plies <NUM> (<FIG>). The controller <NUM> then heats the wound tubular braiding <NUM> to form the composite structure <NUM> (<FIG>).

Referring to <FIG>, an exemplary process flow diagram illustrates a method <NUM> for forming the winding of tubular braiding <NUM> using the system <NUM> described above in <FIG>. The method <NUM> beings at block <NUM>. In block <NUM>, the method <NUM> includes placing the unidirectional tape <NUM> on the mandrel <NUM>. For example, a combination of unidirectional tape 32A, 32B, or 32C may be placed on the mandrel <NUM>. The method <NUM> then proceeds to block <NUM>.

At block <NUM> the unidirectional tape 32A, 32B, and 32C are interlaced together to form the triaxial braid <NUM> (<FIG>). For example, as the mandrel <NUM> moves along the center axis "A", the warp spools 38A and the weft spools 38B counter-rotate. Movement of the mandrel <NUM> draws out the unidirectional tape 32A disposed on the warp spools 38A, the unidirectional tape 32B disposed on the weft spools 32B, and the unidirectional tape 32C disposed on the fixed spools 38C. The counter-rotation of the warp spools 38A and the weft spools 38B interlaces the unidirectional tape 32A from the warp spools 38A with the unidirectional tape 32B from the weft spools 38B and with the unidirectional tape 32C from the fixed spools 38C as the mandrel <NUM> moves along the center axis "A" (<FIG>). At block <NUM> the tubular braiding <NUM> has been formed with a triaxial braid <NUM> (<FIG>). Depending on the configuration of the mandrel <NUM> as noted above, the mandrel <NUM> may be separated from the tubular braiding <NUM> or left in the tubular braiding <NUM>. From block <NUM> or block <NUM>, the method <NUM> proceeds to block <NUM>. Block <NUM> includes winding the tubular braiding <NUM> around the winding tool <NUM>. The winding of the tubular braiding <NUM> forms the wound tubular braiding <NUM> (<FIG>). As noted above, the winding may be done manually or via an automated process using the device <NUM>. The method <NUM> then proceeds to block <NUM>.

Block <NUM> includes slipping or shearing the unidirectional tape <NUM> (<FIG>) relative to one another while winding the tubular braiding <NUM> around the winding tool <NUM>. It is to be appreciated that the unidirectional tape <NUM> slips or shears relative to one another without bending when the tubular braiding <NUM> is wound around the winding tool <NUM>. This results in a wound tubular braiding <NUM> having an increased number of unidirectional tape <NUM> oriented in the same direction as the perimeter of the composite structure <NUM>, which in turn provides improved load bearing capabilities. The disclosed process for fabricating the composite structure <NUM> is faster when compared to conventional lay-up processes, thereby enabling higher production rates. Finally, the disclosed process creates less wasted material when compared to conventional processes.

The system <NUM> described above, as well as the methods <NUM>, <NUM>, <NUM>, and <NUM>, may be employed in the context of an aircraft manufacturing and service method <NUM> as shown in <FIG> and an aircraft <NUM> as shown in <FIG>. During pre-production, exemplary method <NUM> may include specification and design <NUM> of the aircraft <NUM> and material procurement <NUM>. During production, component and subassembly manufacturing <NUM> and system integration <NUM> of the aircraft <NUM> takes place. Thereafter, the aircraft <NUM> may go through certification and delivery <NUM> in order to be placed in service <NUM>. While in service by a customer, the aircraft <NUM> is scheduled for routine maintenance and service <NUM> (which may also include modification, reconfiguration, refurbishment, and so on).

Each of the processes of the systems and methods described herein may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of venders, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on.

As shown in <FIG>, the aircraft <NUM> produced by exemplary method <NUM> may include an airframe <NUM> with a plurality of systems <NUM> and an interior <NUM>. Examples of high-level systems <NUM> include one or more of a propulsion system <NUM>, an electrical system <NUM>, a hydraulic system <NUM>, and an environmental system <NUM>. Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry.

Claim 1:
A composite structure (<NUM>), comprising:
a braid (<NUM>, <NUM>) that is formed into a winding,
wherein the braid (<NUM>, <NUM>) contains, or is formed from, a unidirectional tape (<NUM>) wherein the unidirectional tape (<NUM>) is constructed of unidirectional fibers (<NUM>),
wherein the braid (<NUM>, <NUM>) is one of a biaxial braid (<NUM>) and a triaxial braid (<NUM>).