Inverse identification of material constants of various cohesive laws for delamination of composites using experimental results

Abstract

There are several methods for modeling delamination in composite structures, among which the cohesive zone model (CZM) is one of the best. Various CZMs are implemented through specific constitutive equations. There are several material parameters in the formulation of the CZMs which have a prominent effect on the model’s accuracy. In the present study, an inverse methodology is proposed for obtaining the material constants of various traction-separation laws of the delamination phenomenon in composite materials. Linear, exponential, and a tabular form of cohesive law are utilized in this research to model the delamination phenomenon. Firstly, through some numerical examples, the robustness of the proposed inverse algorithm is assessed, and the effect of measurement error and initial guesses on the performance of the algorithm is studied. Then, two experiments, i.e., the double cantilever beam (DCB) and the end notch flexure (ENF) tests, are performed on specimens made from composite fiberglass. The inverse algorithm is then used to obtain the material constants of the cohesive law, and the results are compared with those obtained from standard tests. It is shown that in comparison with the standard test techniques, the proposed inverse algorithm requires fewer experiments to obtain the material constants while providing reliable results.