Computer-aided photoelastic analysis of orthogonal 3D textile composites: Part 1. Whole-field determination of isochromatics and isoclinics

Two correlative methods are developed for the computer-aided photoelastic analysis of orthogonal 3D textile composites comprising 6 mm×6 mm highly heterogeneous unit cells in-plane. The first method, presented in Part 1, is used for the whole-field determination of isochromatics and isoclinics; the second method, presented in Part 2, is applied for subsequent photoelastic stress analysis. Part 1 delineates precisely how one circular polariscope and two plane polariscope photoelastic images are implemented to extract the isochromatic parameterR and isoclinic parameter α using the digital image processing technique. The photoelastic experiments were performed with orthogonal 3D textile composite as well as aluminum plates containing a hole under the uniaxial tension loading. The obtained values ofR and α, for the case of the aluminum plate, are smoothly distributed over the field and show consistent agreement with those computed from finite element analysis (FEM). In the case of the composite plate, the global distribution ofR and α also agree well with FEM results employing the homogenized composite properties. However, bothR and α exhibit local variations according to the 3D fabric structure, and the varying amplitude of α is relatively larger than that ofR.