Hybrid Dynamic Failure Prediction Tool for Advanced Composite Structures

Abstract

Damage in composite sandwich and laminate structures is characterized by the coexistence of discrete (delamination) and continuum damage (matrix cracking and intralaminar damage). A purely fracture mechanics-based or a purely continuum damage mechanics-based tool alone cannot effecti vely characterize the interaction between the discrete and continuum damage and their cumulative effect, which leads to final rupture. In this paper, a hybrid discrete and continuum damage model is developed and numerically implemented within the LS-DYNA environment via a user-defined material model. The inplane damage resulting from fiber/tow/matrix failure in a woven fabric composite is characterized using a continuum damage model. Discrete delamination damage is captured by a cohesive interface model. The calculated constituent stress and strain are used in a mechanism-driven failure criterion to predict the failure mode, failure sequence, and the synergistic interaction that leads to global stiffness degradation and final rupture. The use of the cohesive interface model can capture the complicated delamination zone without posing the self-similar crack growth condition. Unified depiction of continuum and discrete damage via damage mechanics theory provides a rational way to study the coupling effects between in-plane and out-of-plane failure modes. The applicability of the hybrid dynamic failure prediction tool is demonstrated via its application to 1) a sandwich beam subjected to a low velocity impact; and 2) a z-pinned laminate plate subjected to a high velocity impact.