Strength Prediction of Quasi-Isotropic Scaled Laminates in Open Hole Tension Using Damage Rate Bound Mesomodel

The open hole tension (OHT) test is one of the standard composite material qualification tests at the coupon level. Predicting OHT strengths using finite element models is essential to minimize the number of tests and associated costs. Present article demonstrates the tensile strength prediction of OHT specimens using Ladevèze (LMT-Cachan) mesomodel in conjunction with damage rate bound (DRB) based delay damage. Intra-laminar ply failure and interface failure are taken into account in the current research. These intraply and interface models are coded as user subroutines in LS-Dyna explicit commercial solver. Matrix in-situ strengths are used to account for ply thickness effects in the finite element simulations. Effect of ply, sub-laminate or in-plane scaling effects on OHT strength are investigated. A calibration procedure for the DRB delay damage constants is proposed. The robustness of the DRB delay damage is evaluated in mitigating mesh size effects by considering two types of mesh topologies. All the test data is taken from the scientific literature. Comparison between tests and present finite element predictions is made in terms of failure stress, failure modes and damage sequence events. Predictions from current finite element models matched well in the matrix or delamination failure mode dominated test cases. A reasonably acceptable agreement was observed in test cases with fiber dominant failure.