Deformation and Failure of Angle-Ply Composite Laminates

Abstract

Angle-ply carbon/epoxy composite laminates were tested under uniaxial compression at two strain rates (10⁻⁴ and 1 s⁻¹). In this study, failure is defined as maximum ply damage. This is determined by noting where the stress–strain curve of the laminate reaches a characteristic damage state and the stress–strain behavior reaches a terminal modulus. The characteristic damage state stress is compared to predictions from the recently introduced Northwestern (NU) theory at each strain rate. Residual and interlaminar stresses were considered in the analysis and experiment design. Most classical theories fail to predict the exact failure behavior of the laminates. The NU theory is in good agreement in most cases with the exception of cases where the state of stress includes a non negligible stress component in the fiber direction. However, for determining lamina failure due to matrix dominated failure modes, the NU theory is in excellent agreement with experimental results.