Identification of Cohesive-Zone Laws from Crack-tip Deformation Fields

A hybrid framework for inverse analysis of crack-tip cohesive zone model was developed to determine cohesive zone laws from full-field measurement of crack-tip fields by combining analytical, experimental and numerical approaches. The framework is based on the analytical solution method developed to extract cohesive-zone laws from elastic far-fields by using eigenfunction expansion of cohesive crack-tip fields and path-independent integrals. Electronic Speckle Patten Interferometry (ESPI) was used to provide crack-tip deformation fields as input data for the inverse analysis. To overcome ill-conditioning of the inverse problem, a global noise reduction algorithm was developed by implementing a PDE-constrained error minimization problem. The analytical, experimental and numerical approaches were combined to extract cohesive zone laws of fracture processes in glassy polymers, so called crazing. The results demonstrated that the inverse analysis framework provided a systematic and rigorous method to obtain cohesive-zone laws from experimental measurements, so that more realistic cohesive zone modeling can be achieved to predict fracture processes in various engineering materials and interfaces.