An ABAQUS Implementation of Regularized Extended Finite Element Method (Rx-FEM) for Modeling the Interaction Between Matrix Cracking and Delamination in Composites

Abstract

Regularized Extended Finite Element Method (Rx-FEM) is a discrete damage modeling (DDM) method, which represents an approach to progressive failure analysis (PFA) in composites when multiple individual damage events such as matrix cracks and delamination are introduced into the model via the displacement discontinuities. Rx- FEM is a variant of the eXtended Finite Element Method (x-FEM) where a continuous approximation of Heaviside step function is introduced unlike x-FEM. The proposed implementation to represent the enriched displacement field is based on the superposition of native ABAQUS elements with UMAT and UEL which is used to connect the superimposed elements. Both user subroutines are utilized to facilitate the step function based energy conditions required for mesh independent crack (MIC) propagation within a lamina. In this paper, an interface UEL is developed to connect different unidirectional plies of the laminate for modeling the inter-ply delamination and the interaction between matrix crack and delamination. Several benchmark examples with analytical solutions including the DCB, ENF and TCT models were performed to verify the accuracy of the interface UEL for mode I, mode II fracture, and the interaction between matrix crack and delamination, respectively. The ABAQUS implementation of Rx-FEM not only demonstrates accurate predictions, but also is able to use built-in ABAQUS capabilities such as contact between plies with mesh independent Rx-FEM cracks.