Experimental validation of an empirical nonlinear shear failure model for laminated composite materials

Abstract

This paper aims to develop a numerical nonlinear progressive damage model for laminated composite materials considering in-plane and out-of-plane shear stresses in combination with cohesive interface elements to predict the structural response and the failure mechanisms of laminated composite materials. For this purpose, the constitutive models for intralaminar and interlaminar damage modes have been developed as a numerical code by a UMAT subroutine and implemented in commercial finite element software. This model, which is based on the continuum damage mechanics approach, enables to predict the gradual degradation of material properties with five distinct damage parameters for different failure modes; three of these damage factors apply the shear damage contribution as a separate damage mode by a separate damage factor into the model and characterize it by shear damage dissipation energy, and two parameters for fiber and matrix in transverse directions. Also, a series of experiments have been performed to characterize and validate the nonlinear behavior of glass/epoxy laminate. This model is used to predict the behavior and the final strength of open-hole tension specimens. A reasonably good agreement was also achieved between numerical predictions and experimental observations in terms of shapes, orientations and sizes of individual intraply damages induced around the notch and also the final strength of open-hole tension specimen.