Abstract: Composite structures are fabricated and cured without applying external heat from an autoclave or oven. This technique uses composite preforms to form high strength, three-dimensional co-bonded joints, and thermoplastic conformal mandrels such as rota-molded vacuum bags. The bags form internal tooling within the structure and provide molding with integral fittings that circulate heated air within the bags. The exteriors of the bags are simultaneously under vacuum and exert pressure on the composite elements of the structure that are being cured. This internally-applied heat initially causes to the bags to soften and fully conform to the internal shapes of the structure that are being co-bonded. The heat then transfers into the uncured materials, causing them to cure without unnecessarily heating the entire structure or any required tooling.

Abstract: A method is provided for using a three-dimensional, Pi-shaped, woven preform to assemble first and second composite components. The preform is infused with resin, and at least one surface of the preform is adhered to at least one surface of the first component using a film adhesive. The preform is cured while an oversized tool coated with non-stick material is located within a clevis formed by two legs of the preform. A removable peel ply is located between the tool and the clevis, and semi-rigid over-presses are used during curing. After curing, the tool, over-presses, and peel ply are removed, and adhesive is injected into the clevis. The second component is inserted into the clevis, the adhesive adhering to an inner surface of the clevis and to at least one surface of the second component for retaining the second component within the clevis, the second component having a smaller width than the tool.

Abstract: A method provides for full or partial infusion of resin into three-dimensional, woven textile preforms. Resin film is placed at selected locations adjacent the preform, and the resin film may be separated from other areas of the preform using separator sheets or other materials. The preform is heated and may be vacuum-bagged to apply pressure, or may be rolled or fed through a die. The heat and pressure cause the resin to infuse into the selected areas of the preform adjacent the resin films. The amount of resin in the partial infusion is the same as is necessary to fully infuse the preform, but the resin remains localized in the selected areas until heated again at cure to cause the resin to flow throughout the preform. The method may also be used to fully infuse the preform with resin by providing sufficient temperature and time at that temperature during the initial infusion.

Abstract: A method is provided for using a three-dimensional, Pi-shaped, woven preform to assemble first and second composite components. The preform is infused with resin, and at least one surface of the preform is adhered to at least one surface of the first component using a film adhesive. The preform is cured while an oversized tool coated with non-stick material is located within a clevis formed by two legs of the preform. A removable peel ply is located between the tool and the clevis, and semi-rigid over-presses are used during curing. After curing, the tool, over-presses, and peel ply are removed, and adhesive is injected into the clevis. The second component is inserted into the clevis, the adhesive adhering to an inner surface of the clevis and to at least one surface of the second component for retaining the second component within the clevis, the second component having a smaller width than the tool.

Abstract: A composite panel waffle stiffener has fabric plies pre-cut to a selected pattern and laid on a tool having a waffle configuration. The plies overlap each other to maintain continuity of the structure. The resulting waffle stiffener is then bonded to a panel requiring stiffening. The stiffener is flexible and may be bonded to curved panels. Holes in the stiffener allow access to the volume between the stiffener and the panel for minimizing volume loss within, for example, a wing structure containing fuel and for ventilating air or moisture trapped in the volume.

Abstract: A method is provided for using a woven preform having a base and at least one leg extending from the base. The preform is used to assemble first and second composite laminate components formed from tape or fabric and a resin matrix. Z-pins are inserted into the first component prior to its being cured, forming a stubble extending above a surface of the first component. The uncured preform is placed on the surface of the first component, the stubble extending into the preform. The cured second component is attached to the preform. Over-wrap plies are optionally placed on the outer surfaces of preform. Adhesive is optionally placed between the preform and the first and second components. A vacuum bag and tooling are used while curing the preform to adhere the legs of the preform to the second component and the base of the preform to the first component.

Abstract: A method provides for full or partial infusion of resin into three-dimensional, woven textile preforms. Resin film is placed at selected locations adjacent the preform, and the resin film may be separated from other areas of the preform using separator sheets or other materials. The preform is heated and may be vacuum-bagged to apply pressure, or may be rolled or fed through a die. The heat and pressure cause the resin to infuse into the selected areas of the preform adjacent the resin films. The amount of resin in the partial infusion is the same as is necessary to fully infuse the preform, but the resin remains localized in the selected areas until heated again at cure to cause the resin to flow throughout the preform. The method may also be used to fully infuse the preform with resin by providing sufficient temperature and time at that temperature during the initial infusion.

Abstract: A composite panel waffle stiffener has fabric plies pre-cut to a selected pattern and laid on a tool having a waffle configuration. The plies overlap each other to maintain continuity of the structure. The resulting waffle stiffener is then bonded to a panel requiring stiffening. The stiffener is flexible and may be bonded to curved panels. Holes in the stiffener allow access to the volume between the stiffener and the panel for minimizing volume loss within, for example, a wing structure containing fuel and for ventilating air or moisture trapped in the volume.

Abstract: A three-dimensional weave architecture for weaving preforms has fill fibers woven to provide layer-to-layer interlocking of layers of warp fiber as well as interlocking of fibers within each layer. The woven preform transfers out-of-plane loading through directed fibers to minimize inter-laminar tension. The preform has a base and at least one leg extending from the base, the base and leg each having at least two layers of warp fibers. The fill fibers follow a weave sequence which carries them through part of the base, then into the legs, then through the other portion of the base, and back through the base to return to the starting point of the fill tow. The leg may be connected at a single- or distributed-column intersection, and the intersection may be radiussed. The outer ends of the base and legs may have tapers formed from terminating layers of warp fibers in a stepped pattern.

Abstract: A method provides for full or partial infusion of resin into three-dimensional, woven textile preforms. Resin film is placed at selected locations adjacent the preform, and the resin film may be separated from other areas of the preform using separator sheets or other materials. The preform is heated and may be vacuum-bagged to apply pressure, or may be rolled or fed through a die. The heat and pressure cause the resin to infuse into the selected areas of the preform adjacent the resin films. The amount of resin in the partial infusion is the same as is necessary to fully infuse the preform, but the resin remains localized in the selected areas until heated again at cure to cause the resin to flow throughout the preform. The method may also be used to fully infuse the preform with resin by providing sufficient temperature and time at that temperature during the initial infusion.

Abstract: An apparatus and method for stiffening a panel provides a composite waffle stiffener and the method for constructing the stiffener. A plurality of fabric plies pre-cut to a selected pattern are laid on a tool having a waffle configuration, the plies overlapping each other to maintain continuity of the structure. The resulting waffle stiffener is then bonded to a panel requiring stiffening. The stiffener is flexible and may be bonded to curved panels. Holes in the stiffener allow access to the volume between the stiffener and the panel for minimizing volume loss within, for example, a wing structure containing fuel and for ventilating air or moisture trapped in the volume.

Abstract: A thermoplastic conformal tool/vacuum bag that is structured to substantially conform to a surface or a cavity in a composite structure is placed proximate to a uncured composite member to fabricate a composite structure. External heat and external pressure are applied to cure the member. The conformal thermoplastic tool/vacuum bag is removed from the cured assembly by reheating, if necessary, to facilitate removal of the tool/vacuum bag.

Abstract: A method is provided for using a woven preform having a base and at least one leg extending from the base. The preform is used to assemble first and second composite laminate components formed from tape or fabric and a resin matrix. Z-pins are inserted into the first component prior to its being cured, forming a stubble extending above a surface of the first component. The uncured preform is placed on the surface of the first component, the stubble extending into the preform. The cured second component is attached to the preform. Over-wrap plies are optionally placed on the outer surfaces of preform. Adhesive is optionally placed between the preform and the first and second components. A vacuum bag and tooling are used while curing the preform to adhere the legs of the preform to the second component and the base of the preform to the first component.

Abstract: An apparatus and method for stiffening a panel provides a composite waffle stiffener and the method for constructing the stiffener. A plurality of fabric plies pre-cut to a selected pattern are laid on a tool having a waffle configuration, the plies overlapping each other to maintain continuity of the structure. The resulting waffle stiffener is then bonded to a panel requiring stiffening. The stiffener is flexible and may be bonded to curved panels. Holes in the stiffener allow access to the volume between the stiffener and the panel for minimizing volume loss within, for example, a wing structure containing fuel and for ventilating air or moisture trapped in the volume.

Abstract: A method is provided for securing a three-dimensional woven preform to a first composite laminate component, the preform having a base and at least one leg extending from the base. The preform may be used to attach a second component or may be used alone to stiffen the first component. The preform and the first component are uncured, whereas the second component is cured prior to assembly. The preform is positioned on the first component, adhesive optionally being located between the preform and the first component. Z-pins are driven through the base of the preform and into the first component, the pins extending into the base and the first component. The second component is attached to the leg of the preform. A vacuum bag and tooling are used while curing the first component and the preform and the preform to the first component. The second component may be bonded or fastened to the preform.

Abstract: A method provides for full or partial infusion of resin into three-dimensional, woven textile preforms. Resin film is placed at selected locations adjacent the preform, and the resin film may be separated from other areas of the preform using separator sheets or other materials. The preform is heated and may be vacuum-bagged to apply pressure, or may be rolled or fed through a die. The heat and pressure cause the resin to infuse into the selected areas of the preform adjacent the resin films. The amount of resin in the partial infusion is the same as is necessary to fully infuse the preform, but the resin remains localized in the selected areas until heated again at cure to cause the resin to flow throughout the preform. The method may also be used to fully infuse the preform with resin by providing sufficient temperature and time at that temperature during the initial infusion.

Abstract: A method is provided for using a three-dimensional, Pi-shaped, woven preform to assemble first and second composite components. The preform is infused with resin, and at least one surface of the preform is adhered to at least one surface of the first component using a film adhesive. The preform is cured while an oversized tool coated with non-stick material is located within a clevis formed by two legs of the preform. A removable peel ply is located between the tool and the clevis, and semi-rigid over-presses are used during curing. After curing, the tool, over-presses, and peel ply are removed, and adhesive is injected into the clevis. The second component is inserted into the clevis, the adhesive adhering to an inner surface of the clevis and to at least one surface of the second component for retaining the second component within the clevis, the second component having a smaller width than the tool.

Abstract: A three-dimensional weave architecture for weaving preforms has fill fibers woven to provide layer-to-layer interlocking of layers of warp fiber as well as interlocking of fibers within each layer. The woven preform transfers out-of-plane loading through directed fibers to minimize inter-laminar tension. The preform has a base and at least one leg extending from the base, the base and leg each having at least two layers of warp fibers. The fill fibers follow a weave sequence which carries them through part of the base, then into the legs, then through the other portion of the base, and back through the base to return to the starting point of the fill tow. The leg may be connected at a single- or distributed-column intersection, and the intersection may be radiussed. The outer ends of the base and legs may have tapers formed from terminating layers of warp fibers in a stepped pattern.