Characterization of Interface Shear Stress-Strain and Mode II Fracture Properties Using DIC in Thick Adherent Shear Tests

Abstract

Progressive damage and failure analysis tools for fiber reinforced laminated composites are sensitive to material input parameters for a wide range of failure modes. Without accurate stress-strain and fracture properties, these analyses tools will not be effective. Delaminations are the critical failure mode for this study’s focus, which aims to develop a method to measure interfacial stress-strain and fracture behavior in mode II, increasing confidence in the material input data for these failure models. A direct method of measurement is proposed to observe interface behavior under loading and fracture. High-resolution Digital Image Correlation techniques are used to measure deformations along the bondline in thick adherend shear specimens, which provide the necessary data to characterize the interface behavior. By using constrained optimization techniques on overdetermined data, the material behavior may be solved without the need for closed-form solutions nor relying on expensive iterative finite element analysis. A virtual study in the finite element environment is performed to verify the method, after which the method is applied to carbon fiber skins co-cured with an adhesive layer.