# US 12,759,248 B2 · Methods for manufacturing hat-stiffened structures > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,759,248 B2 - Document ID: US12759248B2 - Status: Granted - Kind: B2 - Application number: 18/065,458 - Filed: 2022-12-13 - Published: 2024-06-13 - Granted: 2026-10-13 - Earliest claimed: 2022-12-13 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: Thomas Karl Tsotsis; Andrew Milton Harber - Web page: https://patentgrep.com/patent/US12759248B2 ## CPC - B29C 70/48: and impregnating the reinforcements in the closed mould, e.g. resin transfer moulding [RTM] {, e.g. by vacuum} - B29C 70/226: {the structure comprising mainly parallel filaments interconnected by a small number of cross threads} - B29L 2031/003: {having a profiled transverse cross-section} - B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00) - B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES ## Abstract Stiffened composite skin and methods of manufacture. A dry, hat-shaped preform is applied into a recess in a lower mold tool. A first set of dry, skin-preform layers is applied over the dry, hat-shaped preform to form a dry preform assembly. Resin is infused into the dry preform assembly to form a resin-infused preform. The resin-infused preform is cured in situ to form the stiffened composite skin. ## Claims ### Claim 1 A method of manufacturing a stiffened composite skin comprising: applying a dry, hat-shaped preform into a recess in a lower mold tool; applying a first set of dry, skin-preform layers over the dry, hat-shaped preform to form a dry preform assembly; applying a second set of dry, skin-preform layers onto the lower mold tool, wherein applying the dry, hat-shaped preform into the recess further comprises placing the dry, hat-shaped preform in contact with the second set of dry, skin-preform layers to form a joint without extending into the recess; infusing resin into the dry preform assembly to form a resin-infused preform; and curing the resin-infused preform in situ to form the stiffened composite skin. ### Claim 2 (depends on 1) The method of claim 1 further comprising: lowering an upper mold tool over the dry preform assembly to form a vacuum-sealed perimeter around the dry preform assembly prior to infusing the resin, wherein the upper mold tool and the lower mold tool together form a tool, and wherein infusing the resin into the dry preform assembly is performed while the dry preform assembly is within the vacuum-sealed perimeter. ### Claim 3 (depends on 2) The method of claim 2 further comprising: closing the upper mold tool onto the resin-infused preform to encapsulate the resin-infused preform to net cured-part dimensions prior to curing the resin-infused preform. ### Claim 4 (depends on 2) The method of claim 2 further comprising: opening the tool by separating the upper mold tool and the lower mold tool for removal of the stiffened composite skin from the lower mold tool; and post-processing the stiffened composite skin after removal from the lower mold tool. ### Claim 5 (depends on 1) The method of claim 1 further comprising: applying a reusable tool inside the dry, hat-shaped preform, the reusable tool possessing a geometry of an inside of the dry, hat-shaped preform. ### Claim 6 (depends on 1) The method of claim 1 further comprising: laying up a warp-knit fabric containing a thermoplastic veil to form a stiffener preform. ### Claim 7 (depends on 6) The method of claim 6 further comprising: preforming the stiffener preform to a near-net shape to form the dry, hat-shaped preform. ### Claim 8 (depends on 7) The method of claim 7, wherein: preforming the stiffener preform comprises applying heat and pressure to the stiffener preform to tack together the warp-knit fabric using the thermoplastic veil and to form the dry, hat-shaped preform that is semi-rigid. ### Claim 9 (depends on 1) The method of claim 1, wherein applying the dry, hat-shaped preform into the recess comprises forming the dry, hat-shaped preform to a net shape. ### Claim 10 (depends on 1) The method of claim 1, wherein the dry, hat-shaped preform is slightly tapered from a first end to a second end longitudinally to enable easier removal of the stiffened composite skin after infusing resin and curing. ### Claim 11 (depends on 1) The method of claim 1, wherein applying the first set of dry, skin-preform layers over the dry, hat-shaped preform further comprises applying the first set of dry, skin-preform layers over the second set of dry, skin-preform layers. ### Claim 12 (depends on 11) The method of claim 11, wherein applying a dry, hat-shaped preform in contact with the second set of dry, skin-preform layers forms scarf joints. ### Claim 13 (depends on 11) The method of claim 11, wherein applying a dry, hat-shaped preform in contact with the second set of dry, skin-preform layers forms butt joints. ### Claim 14 (depends on 11) The method of claim 11 further comprising: stitching through flanges of the dry, hat-shaped preform, the first set of dry, skin-preform layers, and the second set of dry, skin-preform layers. ### Claim 15 (depends on 1) The method of claim 1 further comprising stitching connecting flanges of the dry, hat-shaped preform to the first set of dry, skin-preform layers. ### Claim 16 A method of manufacturing a stiffened composite skin comprising: laying up a dry preform assembly comprising a second set of dry, skin-preform layers, a dry, hat-shaped preform with flanges in contact with the second set of dry, skin-preform layers, and a first set of dry, skin-preform layers positioned over and in contact with the dry, hat-shaped preform and the second set of dry, skin-preform layers, wherein laying up the dry preform assembly comprises applying the dry, hat-shaped preform in contact with the second set of dry, skin-preform layers to form a joint comprising at least one of a scarf joint, a butt joint, or an interleaved joint; and infusing resin into the dry preform assembly. ### Claim 17 (depends on 16) The method of claim 16, wherein laying up the dry preform assembly comprises applying the dry, hat-shaped preform in contact with the second set of dry, skin-preform layers to form scarf joints. ### Claim 18 (depends on 16) The method of claim 16, wherein laying up the dry preform assembly comprises applying the dry, hat-shaped preform in contact with the second set of dry, skin-preform layers to form butt joints. ### Claim 19 (depends on 16) The method of claim 16 further comprising: preforming a stiffener preform comprising warp-knit fabric with a thermoplastic veil into the dry, hat-shaped preform having a semi-rigid near-net shape tacked by the thermoplastic veil. ### Claim 20 (depends on 19) The method of claim 19, wherein preforming the stiffener preform comprises applying heat and pressure to the stiffener preform to tack together the warp-knit fabric using the thermoplastic veil and to form the dry, hat-shaped preform that is semi-rigid. ### Claim 21 (depends on 19) The method of claim 19 wherein infusing the dry preform assembly forms a resin-infused preform, the method further comprising: curing the resin-infused preform in situ to form the stiffened composite skin. ### Claim 22 (depends on 21) The method of claim 21 further comprising: lowering an upper mold tool over the dry preform assembly to form a vacuum-sealed perimeter around the dry preform assembly prior to infusing the resin, wherein the upper mold tool and a lower mold tool together form a tool, and wherein infusing the resin into the dry preform assembly is performed while the dry preform assembly is within the vacuum-sealed perimeter. ### Claim 23 (depends on 22) The method of claim 22 further comprising: closing the upper mold tool onto the resin-infused preform to encapsulate the resin-infused preform to net cured-part dimensions prior to curing the resin-infused preform. ### Claim 24 (depends on 16) The method of claim 16, wherein laying up the dry preform assembly comprises applying a reusable tool inside the dry, hat-shaped preform, the reusable tool possessing a geometry of an inside of the dry, hat-shaped preform. ### Claim 25 (depends on 16) The method of claim 16, wherein laying up the dry preform assembly further comprises stitching the flanges to the second set of dry, skin-preform layers and the first set of dry, skin-preform layers. ### Claim 26 (depends on 16) The method of claim 16, wherein the second set of dry, skin-preform layers have a greater thickness than a thickness than the flanges of the dry, hat-shaped preform. ### Claim 27 (depends on 16) The method of claim 16, wherein the dry, hat-shaped preform and the second set of dry, skin-preform layers form interleaved joints. ### Claim 28 (depends on 16) The method of claim 16, wherein the dry, hat-shaped preform is semi-rigid and tacked together with a thermally activated binder. ### Claim 29 (depends on 16) The method of claim 16, wherein the dry, hat-shaped preform comprises warp-knit fabric.