# US 2019/0318444 A1 · Method and means to analyze thermographic data acquired during automated fiber placement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0318444 A1 - Document ID: US20190318444A1 - Status: Published application - Kind: A1 - Application number: 15/954,126 - Filed: 2018-04-16 - Published: 2019-10-17 - Earliest claimed: 2018-04-16 - Assignees: United States of America as represented by the Administrator of NASA - Applicants: Untited States of America as represented by the Administrator of NASA - Inventors: Peter D. Juarez; ELIZABETH D. GREGORY; K. ELLIOTT CRAMER - Web page: https://patentgrep.com/patent/US20190318444A1 ## CPC - B29C 70/382: {Automated fiber placement [AFP]} - B29C 70/384: {Fiber placement heads, e.g. component parts, details or accessories} - G01J 5/0022: {for sensing the radiation of moving bodies} - G01J 5/047: {Mobile mounting; Scanning arrangements} - G01J 5/10: using electric radiation detectors - G01N 21/8851: {Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges (G01N21/8806 and G01N21/93 - G01N21/95692 take precedence; optical measurement of dimensions G01B11/00; optical scanning G02B26/10; image transformation G06T3/00; computerised image enhancement G06T5/00; image processing per se for flaw detection G06T7/0002)} - G01N 25/72: Investigating presence of flaws - G06T 1/0014: {Image feed-back for automatic industrial control, e.g. robot with camera (robots B25J19/023)} - G06T 7/0004: {Industrial image inspection} - G06T 7/90: Determination of colour characteristics - H04N 23/23: from thermal infrared radiation - G01J 5/48: Thermography; Techniques using wholly visual means - G01J 2005/0077: {Imaging} - G01N 2021/8444: {Fibrous material} - G01N 2021/8472: {Investigation of composite materials} - G06T 2207/10048: Infrared image - G06T 2207/30124: Fabrics; Textile; Paper - 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) - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract A method of detecting defects in a composite structure includes applying heat to a surface of a composite structure. Thermographic images or frames captured by a moving camera may be utilized to corm temporally aligned images that include temperature data (pixals) from a plurality of frames, wherein the pixals comprise data captured at a simple (uniform) time delay from the time at which heat was applied. The temporally aligned thermographic data for the surface region may include variations due to differences in thermal transients caused by defects in the composite structure. The variations in the thermographic data may be utilized to detect one or more defects in the composite structure. ## Claims ### Claim 1 A method of detecting defects in a composite structure fabricated by an automated fiber placement (AFP) process, the method comprising: applying heat to the surface of a composite structure using a heat source that moves relative to the composite structure; capturing a series of initial thermographic images of the surface of the composite structure after heating the surface using a camera that moves with the heat source relative to the composite structure; forming temporally synchronized images comprising sections of a plurality of the initial thermographic images, wherein the sections correspond to portions of the surface that were heated at the same time interval prior to capturing the image section; wherein the temporally synchronized images include variations; utilizing variations in the thermographic data for the surface to detect one or more defects in the composite structure. ### Claim 2 (depends on 1) The method of claim 1, wherein: the sections of the initial thermographic images comprise pixels. ### Claim 3 (depends on 2) The method of claim 2, including: using the series of initial thermographic images to form a data cube having two spatial dimensions and one time dimension. ### Claim 4 (depends on 1) The method of claim 1, wherein: forming at least one temporally synchronized image includes time shifting a plurality of pixels to correct for heating delay in the initial thermographic images. ### Claim 5 (depends on 4) The method of claim 4, including: correcting the temporally synchronized images to compensate for varying amounts of heat being applied to the composite structure over time. ### Claim 6 (depends on 5) The method of claim 5, including: determining an expected value of a temperature for the pixels in the temporally synchronized images utilizing correction weights based on overall heating trends. ### Claim 7 (depends on 6) The method of claim 6, including: determining if deviations from the expect values has occurred. ### Claim 8 (depends on 7) The method of claim 7, including: utilizing deviations from the expected values to determine if defects are present in the composite structure. ### Claim 9 (depends on 1) The method of claim 1, wherein: the composite structure is fabricated utilizing an automated fiber placement (AFP) system having a head including a tow applicator that moves relative to the composite structure and applies at least one tow during fabrication of the composite structure; and the thermographic data is captured by at least one thermal camera mounted to the head after the at least one tow is applied. ### Claim 10 (depends on 9) The method of claim 9, wherein: the selected surface region is heated utilizing a lamp mounted on the head whereby a surface of the composite structure is heated before the at least one tow is applied. ### Claim 11 (depends on 10) The method of claim 10, wherein: the at least one thermal camera captures sets of thermographic data at a rate of at least about 60 frames per second while the head is moving relative to the composite structure. ### Claim 12 (depends on 6) The method of claim 6, wherein: the temporally synchronized images include color and/or intensity variations corresponding to differences in surface temperatures caused by defects in the composite structure. ### Claim 13 (depends on 12) The method of claim 12, wherein: the at least one defect comprises a material state. ### Claim 14 (depends on 12) The method of claim 12, wherein: the at least one defect is selected from the group consisting of insufficient tow adhesion, tow buckling, tow lift off, tow disbonding, and tow slippage. ### Claim 15 (depends on 1) The method of claim 1, including: forming first and second temporally synchronized images using thermographic images captured before and after, debulking the composite structure, respectively; detecting changes in the composite structure caused by the debulking process utilizing differences between the first and second temporally synchronized images. ### Claim 16 (depends on 10) The method of claim 10, including: collecting thermographic images after a final ply of the composite structure has been laid utilizing at least one thermal camera mounted to a tow-dispensing head of an automated fiber placement (AFP) system. ### Claim 17 A method of evaluating physical properties of a fiber reinforced composite structure, the method comprising: heating at least a portion of the composite structure using a heat source that moves relative to the composite structure; capturing a series of groups of thermographic image data of the surface of the composite structure after heating the composite structure using a thermographic camera that moves relative to the composite structure; time shifting thermographic image data from a plurality of the groups of thermographic image data to form at least one temporally synchronized image comprising thermographic image data for a surface region at equal times from heating; and utilizing variations in the at least one thermographic synchronized image to identify defects in the composite structure. ### Claim 18 (depends on 17) The method of claim 17, including: applying a tow to a heated surface of the composite structure; capturing thermographic image data from a surface of the tow after the tow has been applied to the heated surface. ### Claim 19 (depends on 17) The method of claim 17, including: forming a plurality of temporally synchronized images; and comparing the temporally synchronized images to determine if defects are present in the composite structure. ### Claim 20 (depends on 19) The method of claim 19, wherein: the groups of thermographic image data comprise frames having a plurality of pixels, the frames forming a data cube having two spatial dimensions and one time dimension; and wherein pixels are time shifted to align heating curves of the pixels to form the temporally synchronized images.