Hybridized 3-D Photogrammetry Strain Analysis for Sandwich Structures (1001-609)

Triton Systems Inc. will in this Phase I apply 3-D digital image correlation to obtain and process full-field strain imagery of critical composite honeycomb structures to produce full-field images of structural safety margins. While the technology for obtaining surface strains via photogrammetry has been commercially available for several years, our novel data processing software will provide design and manufacturing engineers with powerful tools for composite sandwich structures by: Identifying the influence of design details and discontinuities on overall structural integrity. Evaluating non-conforming part integrity, in support of material disposition. Developing and evaluating repair procedures. Evaluating the effect of executed repairs on the integrity of the composite sandwich. The Phase I goal will be to produce maps of structural safety margin on loaded virgin, damaged and damaged/repaired sandwich structures, using the ability of digital image correlation to distinguish in-plane and out-of-plane strain components, combined with the laminate properties. A series panel tests will assist in developing the correlation between the semi-empirical strain/margin maps and actual sandwich failures. The outline of a user-friendly software system to process measured strain maps into safety margin contours will also be produced, which system will be the subject of Phase II developments. BENEFIT: The benefit of the developed semi-empirical composite sandwich design and evaluation system is that the availability of full-field strain and structural safety margin maps will provide both the design engineer and the manufacturing/QC engineer with direct and comprehensive feedback concerning the integrity of sandwich structures. We envision several distinct outputs from this project, including principally an integrated measurement/analysis tool for producing the strain/safety margin maps for specific design configurations and a handbook or database of typical composite sandwich configurations; virgin, damaged and repaired, with associated structural safety margin maps for simplified loadings so that the engineer can rationally judge both the impact of specific defects upon structure integrity and the advisability of various repair strategies.