A Stabilized Finite Element Method for Modeling Mixed-mode Delamination of Composites

Abstract

Delamination of composite materials is commonly modeled using intrinsic cohesive zone models (CZMs), which are generally incorporated into the standard finite element (FE) method through a zero-thickness interface (cohesive) element; however, intrinsic CZMs exhibit numerical instabilities when the cohesive stiffness parameters is assumed to be large relative to the elastic stiffness of the composite material. To address this numerical instability issue, we propose a stabilized finite element method by combining the traditional penalty method with the Nitsche’s method that is equally effective for any specified initial stiffness of the cohesive (traction-separation) law. The key advantage of the proposed method is that it generalizes the Nitsche’s method to any tractionseparation law with arbitrary large values of initial stiffness and provides a unified way to treat cohesive fracture problems in a variationally consistent and stable manner. We implemented the stabilized method in the commercial finite element software Abaqus via the user element subroutine and simulated benchmark tests for mode I and mixed-mode delamination in isotropic materials to establish the viability of the approach. Ongoing work is aimed at extending the method to model delamination in transversely isotropic laminated composites.