# US 11,298,899 B2 · System and method for repairing a composite structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,298,899 B2 - Document ID: US11298899B2 - Status: Granted - Kind: B2 - Application number: 16/450,739 - Filed: 2019-06-24 - Published: 2020-12-24 - Granted: 2022-04-12 - Earliest claimed: 2019-06-24 - Assignees: Textron Innovations Inc. - Applicants: Bell Helicopter Textron Inc. - Inventors: Suvankar Mishra; Vance Newton Cribb, III - Web page: https://patentgrep.com/patent/US11298899B2 ## CPC - B29C 73/025: {fed under pressure} - B29C 73/00: Repairing of articles made from plastics or substances in a plastic state, e.g. of articles shaped or produced by using techniques covered by this subclass or subclass B29D ({linings for tyres acting locally B60C5/142;} retreading tyres B29D30/54; devices for covering leaks in pipes or hoses F16L55/16) - B29C 73/02: using liquid or paste-like material (B29C73/16 takes precedence) - B29C 73/10: using patches sealing on the surface of the article (B29C73/14 takes precedence) - B29C 73/24: Apparatus or accessories not otherwise provided for - B64C 11/26: Fabricated blades - B64F 5/40: Maintaining or repairing aircraft - B29C 44/18: Filling preformed cavities {(B29C44/1204 takes precedence)} - B29C 65/542: {by injection} - B29L 2031/082: {Blades, e.g. for helicopters} - B29L 2031/608: {Honeycomb structures} - B32B 2603/00: Vanes, blades, propellers, rotors with blades - 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) - B64C: AEROPLANES; HELICOPTERS - B64F: GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR - B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES - B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM ## Abstract A method of repairing a composite structure includes providing an assembled composite structure comprising a substantially rigid outer component, wherein the composite structure comprises a void space at least partially bounded by the outer component. The method further includes forming an injection hole through the outer component to provide a path between the void space and space external to the composite structure. The method further includes injecting foam into the void space through the injection hole while the foam is in a substantially unexpanded state and expanding the foam within the void space. ## Claims ### Claim 1 A method of repairing a composite structure, comprising: providing an assembled composite structure comprising a first outer component, a second outer component, and a void space between the first outer component and the second outer component; forming an injection hole through the first outer component to provide a path between the void space and space external to the composite structure; injecting foam into the void space through the injection hole while the foam is in a substantially unexpanded state; and expanding the foam within the void space, wherein upon expansion, the foam contacts an expanded adhesive that is disposed between a spar and the void space. ### Claim 2 (depends on 1) The method of claim 1, wherein the composite structure comprises a rotor blade. ### Claim 3 (depends on 2) The method of claim 2, wherein the void space is disposed between the spar of the rotor blade and a honeycomb structure of the rotor blade. ### Claim 4 (depends on 2) The method of claim 2, wherein the first outer component comprises a skin of the rotor blade. ### Claim 5 (depends on 1) The method of claim 1, further comprising: prior to forming the injection hole, performing a nondestructive evaluation of the composite structure to identify the void space. ### Claim 6 (depends on 5) The method of claim 5, further comprising: applying masking tape to the composite structure around an area of the first outer component identified as being associated with the identified void space. ### Claim 7 (depends on 6) The method of claim 6, wherein the forming the injection hole is conducted after applying the masking tape. ### Claim 8 (depends on 7) The method of claim 7, further comprising: vacuum cleaning the void space. ### Claim 9 (depends on 8) The method of claim 8, further comprising: removing paint from the area of the first outer component. ### Claim 10 (depends on 9) The method of claim 9, further comprising: passing light through the composite component along a path through the second outer component, the void space, and the injection hole; and capturing an image of the light passed through the composite component before injecting the foam. ### Claim 11 (depends on 10) The method of claim 10, further comprising: capturing an image of light passed through the injected foam after the foam is injected and expanded. ### Claim 12 (depends on 1) The method of claim 1, further comprising: forming a relief hole through at least one of the first outer component and the second outer component. ### Claim 13 (depends on 12) The method of claim 12, wherein the relief hole is obstructed while the foam is injected. ### Claim 14 (depends on 13) The method of claim 13, wherein the relief hole is unobstructed after the foam is injected. ### Claim 15 (depends on 12) The method of claim 12, wherein the foam is allowed to expand within the void space and excess expanded foam is allowed to exit the void space via at least one of the injection hole and the relief hole. ### Claim 16 (depends on 1) The method of claim 1, wherein at least a portion of the foam expands and exits the void space via the injection hole, wherein the foam cures after passage of time, and wherein the expanded and cured foam is machined to provide a surface profile substantially continuous with a profile of at least one of the first outer component and the second outer component. ### Claim 17 (depends on 16) The method of claim 16, further comprising: replacing paint removed from the first outer component. ### Claim 18 (depends on 1) The method of claim 1: wherein the composite structure has a repair specification requirement that when the first outer component comprises a damage hole having a given minimum damage hole diameter, a patch of material other than foam or paint is required to cover the damage hole; wherein the injection hole has a diameter smaller than the minimum damage hole diameter so that no patch comprising materials other than the foam and paint is required to cover the injection hole; and wherein the method further comprises measuring the damage hole diameter and determining, as a function of the damage hole diameter, whether a patch comprising material other than the foam or paint is required. ### Claim 19 (depends on 18) The method of claim 18, further comprising: providing a relief hole comprising a diameter smaller than the diameter of the injection hole. ### Claim 20 A method of repairing a rotor blade, comprising: providing a rotor blade comprising a void space between a spar of the rotor blade and a honeycomb structure of the rotor blade, the void space extending from an upper skin of the rotor blade to a lower skin of the rotor blade; forming an injection hole through at least one of the upper skin and the lower skin; and injecting foam into the void space via the injection hole; wherein an expanded adhesive is disposed between the spar and the void space. ### Claim 21 A method of repairing a composite structure, comprising: providing an assembled composite structure comprising a first outer component, a second outer component, and a void space between the first outer component and the second outer component; forming an injection hole through the first outer component to provide a path between the void space and space external to the composite structure; injecting foam into the void space through the injection hole while the foam is in a substantially unexpanded state; expanding the foam within the void space, wherein upon expansion, the foam at least one of (1) contacts an innermost wall of at least one of the first outer component and second outer component and (2) contacts an expanded adhesive that is disposed between a spar and the void space; prior to forming the injection hole, performing a nondestructive evaluation of the composite structure to identify the void space; applying masking tape to the composite structure around an area of the first outer component identified as being associated with the identified void space; vacuum cleaning the void space; and removing paint from the area of the first outer component; wherein the forming the injection hole is conducted after applying the masking tape.