FINITE ELEMENT ANALYSIS OF COMPOSITE LAMINATES CONTAINING TRANSVERSE CRACKS

Abstract

In the field of damage mechanics, the stiffness loss of general composite laminates with transverse cracks can be theoretically related to internal state variables (ISVs) which are dependent on crack densities, ply constraints and crack opening profiles. In present project, an eight-node quadrilateral finite element using the internal state variables is developed to predict the stiffness reduction for cross-ply and angle-ply composite laminates. Examples of the behavior of unnotched graphite/epoxy (gr/ep) and glass/epoxy (gl/ep) laminates, and notched graphite/epoxy laminates are investigated using this finite element method. The determination of the ISVs for both Mode I and Mode II cracking by a series of finite element studies on the kinematic response of transverse cracks at varying crack densities is also discussed. The finite element formulations to form global system stiffness matrix, applied nodal force vector and equilibrium damage force vector are derived. A computer algorithm based on the finite element model are written to predict the stress-strain relationship, damage evolution and stiffness reduction of several general unnotched and notched composite laminates. The predictions are compared with the experimental results published by other researchers and generally good agreements are shown.