# US 10,311,183 B2 · Analysis of a repaired composite structure > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,311,183 B2 - Document ID: US10311183B2 - Status: Granted - Kind: B2 - Application number: 15/476,420 - Filed: 2017-03-31 - Published: 2018-10-04 - Granted: 2019-06-04 - Earliest claimed: 2017-03-31 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: Zuo Sun; William T. Williams; Agung Soehedi - Web page: https://patentgrep.com/patent/US10311183B2 ## CPC - G06F 30/23: using finite element methods [FEM] or finite difference methods [FDM] - B29C 70/38: Automated lay-up, e.g. using robots, laying filaments according to predetermined patterns {(application heads for tyres B29D30/28)} - G05B 11/011: {details of the correcting means} - G06F 30/00: Computer-aided design [CAD] - G06F 30/10: Geometric CAD - B29L 2031/3076: {Aircrafts (blades, propellers B29L2031/08)} - G06F 2113/24: Sheet material - G06F 2113/26: Composites - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - 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) - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) - B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES ## Abstract A method is provided for analyzing a repaired composite structure composed of a plurality of original plies and additional repair plies at an area of repair. The method includes performing a finite element analysis of a finite element model of the repaired composite structure, the finite element analysis being performed to determine in-situ strains at midplanes of the plurality of original plies and the additional repair plies. The method includes determining in-situ strains at top and bottom surfaces of the plurality of original plies and the additional repair plies from the midplane in-situ strains. The method includes determining a margin of safety for the repaired composite structure from in-situ strain data selected from the midplane in-situ strains and surface in-situ strains. And the method includes outputting the margin of safety from which to, or an indication to, accept or reject the repaired composite structure based on the margin of safety. ## Claims ### Claim 1 An apparatus for implementation of a system for analyzing a repaired composite structure composed of a plurality of original plies and additional repair plies at an area of repair, each ply including a top surface, a midplane and a bottom surface, the apparatus comprising a processor and a memory storing executable instructions that, in response to execution by the processor, cause the apparatus to at least: perform a finite element analysis of a finite element model of the repaired composite structure composed of a plurality of finite elements for the plurality of original plies and the additional repair plies, the finite element analysis being performed to determine in-situ strains at the midplanes of and thereby midplane in-situ strains at the plurality of original plies and the additional repair plies; determine in-situ strains at the top surface and the bottom surface of and thereby surface in-situ strains at the plurality of original plies and the additional repair plies from the midplane in-situ strains; determine a margin of safety for the repaired composite structure from in-situ strain data selected from the midplane in-situ strains and surface in-situ strains; and output the margin of safety from which to accept or reject the repaired composite structure, or an indication to accept or reject the repaired composite structure based on the margin of safety. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the apparatus being caused to determine the surface in-situ strains includes being caused to interpolate or extrapolate the surface in-situ strains from the midplane in-situ strains. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the apparatus being caused to determine the margin of safety includes being caused to determine an in-plane margin of safety based on a ratio of an allowable in-plane strain and an average of the midplane in-situ strains, and a bending margin of safety based on a ratio of an allowable bending strain and a maximum of the surface in-situ strains. ### Claim 4 (depends on 3) The apparatus of claim 3, wherein the apparatus being caused to determine the margin of safety includes being caused to determine a minimum of the in-plane margin of safety and the bending margin of safety and thereby the margin of safety for the repaired composite structure. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the repaired composite structure is a repaired composite sandwich structure composed of two fiber-reinforced composite face sheets and a core, each of the two fiber-reinforced composite face sheets including a plurality of original plies, one of the two fiber-reinforced composite face sheets including the additional repair plies, and wherein the apparatus being caused to determine the margin of safety includes being caused to determine an in-plane margin of safety for each fiber-reinforced composite face sheet based on a ratio of an allowable in-plane strain and an average of the midplane in-situ strains in plies of the fiber-reinforced composite face sheet, including the original plies and the additional repair plies in the one of the two fiber-reinforced composite face sheets that includes the additional repair plies. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the apparatus being caused to determine the in-plane margin of safety includes being caused to determine in-plane margins of safety for combined loads and moments applied parallel, tangential and perpendicular to fibers in the two fiber-reinforced composite face sheets. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the repaired composite structure is a repaired composite sandwich structure composed of two fiber-reinforced composite face sheets and a core, and wherein the apparatus being caused to determine the margin of safety includes being caused to determine a bending margin of safety based on a ratio of an allowable bending strain and a maximum of the surface in-situ strains. ### Claim 8 A method for analyzing a repaired composite structure composed of a plurality of original plies and additional repair plies at an area of repair, each ply including a top surface, a midplane and a bottom surface, the method comprising: performing a finite element analysis of a finite element model of the repaired composite structure composed of a plurality of finite elements for the plurality of original plies and the additional repair plies, the finite element analysis being performed to determine in-situ strains at the midplanes of and thereby midplane in-situ strains at the plurality of original plies and the additional repair plies; determining in-situ strains at the top surface and the bottom surface of and thereby surface in-situ strains at the plurality of original plies and the additional repair plies from the midplane in-situ strains; determining a margin of safety for the repaired composite structure from in-situ strain data selected from the midplane in-situ strains and surface in-situ strains; and outputting the margin of safety from which to accept or reject the repaired composite structure, or an indication to accept or reject the repaired composite structure based on the margin of safety. ### Claim 9 (depends on 8) The method of claim 8, wherein determining the surface in-situ strains includes interpolating or extrapolating the surface in-situ strains from the midplane in-situ strains. ### Claim 10 (depends on 8) The method of claim 8, wherein determining the margin of safety includes determining an in-plane margin of safety based on a ratio of an allowable in-plane strain and an average of the midplane in-situ strains, and a bending margin of safety based on a ratio of an allowable bending strain and a maximum of the surface in-situ strains. ### Claim 11 (depends on 10) The method of claim 10, wherein determining the margin of safety includes determining a minimum of the in-plane margin of safety and the bending margin of safety and thereby the margin of safety for the repaired composite structure. ### Claim 12 (depends on 8) The method of claim 8, wherein the repaired composite structure is a repaired composite sandwich structure composed of two fiber-reinforced composite face sheets and a core, each of the two fiber-reinforced composite face sheets including a plurality of original plies, one of the two fiber-reinforced composite face sheets including the additional repair plies, and wherein determining the margin of safety includes determining an in-plane margin of safety for each fiber-reinforced composite face sheet based on a ratio of an allowable in-plane strain and an average of the midplane in-situ strains in plies of the fiber-reinforced composite face sheet, including the original plies and the additional repair plies in the one of the two fiber-reinforced composite face sheets that includes the additional repair plies. ### Claim 13 (depends on 12) The method of claim 12, wherein determining the in-plane margin of safety includes determining in-plane margins of safety for combined loads and moments applied parallel, tangential and perpendicular to fibers in the two fiber-reinforced composite face sheets. ### Claim 14 (depends on 8) The method of claim 8, wherein the repaired composite structure is a repaired composite sandwich structure composed of two fiber-reinforced composite face sheets and a core, and wherein determining the margin of safety includes determining a bending margin of safety based on a ratio of an allowable bending strain and a maximum of the surface in-situ strains. ### Claim 15 A computer readable medium for analyzing a repaired composite structure composed of a plurality of original plies and additional repair plies at an area of repair, each ply including a top surface, a midplane and a bottom surface, the computer-readable storage medium being non-transitory and having computer-readable program code portions stored therein that, in response to execution by a processor, cause an apparatus to at least: perform a finite element analysis of a finite element model of the repaired composite structure composed of a plurality of finite elements for the plurality of original plies and the additional repair plies, the finite element analysis being performed to determine in-situ strains at the midplanes of and thereby midplane in-situ strains at the plurality of original plies and the additional repair plies; determine in-situ strains at the top surface and the bottom surface of and thereby surface in-situ strains at the plurality of original plies and the additional repair plies from the midplane in-situ strains; determine a margin of safety for the repaired composite structure from in-situ strain data selected from the midplane in-situ strains and surface in-situ strains; and output the margin of safety from which to accept or reject the repaired composite structure, or an indication to accept or reject the repaired composite structure based on the margin of safety. ### Claim 16 (depends on 15) The computer readable medium of claim 15, wherein the apparatus being caused to determine the surface in-situ strains includes being caused to interpolate or extrapolate the surface in-situ strains from the midplane in-situ strains. ### Claim 17 (depends on 15) The computer readable medium of claim 15, wherein the apparatus being caused to determine the margin of safety includes being caused to determine an in-plane margin of safety based on a ratio of an allowable in-plane strain and an average of the midplane in-situ strains, and a bending margin of safety based on a ratio of an allowable bending strain and a maximum of the surface in-situ strains. ### Claim 18 (depends on 17) The computer readable medium of claim 17, wherein the apparatus being caused to determine the margin of safety includes being caused to determine a minimum of the in-plane margin of safety and the bending margin of safety and thereby the margin of safety for the repaired composite structure. ### Claim 19 (depends on 15) The computer readable medium of claim 15, wherein the repaired composite structure is a repaired composite sandwich structure composed of two fiber-reinforced composite face sheets and a core, each of the two fiber-reinforced composite face sheets including a plurality of original plies, one of the two fiber-reinforced composite face sheets including the additional repair plies, and wherein the apparatus being caused to determine the margin of safety includes being caused to determine an in-plane margin of safety for each fiber-reinforced composite face sheet based on a ratio of an allowable in-plane strain and an average of the midplane in-situ strains in plies of the fiber-reinforced composite face sheet, including the original plies and the additional repair plies in the one of the two fiber-reinforced composite face sheets that includes the additional repair plies. ### Claim 20 (depends on 19) The computer readable medium of claim 19, wherein the apparatus being caused to determine the in-plane margin of safety includes being caused to determine in-plane margins of safety for combined loads and moments applied parallel, tangential and perpendicular to fibers in the two fiber-reinforced composite face sheets. ### Claim 21 (depends on 15) The computer readable medium of claim 15, wherein the repaired composite structure is a repaired composite sandwich structure composed of two fiber-reinforced composite face sheets and a core, and wherein the apparatus being caused to determine the margin of safety includes being caused to determine a bending margin of safety based on a ratio of an allowable bending strain and a maximum of the surface in-situ strains.