The Effect of Out-of-Plane Waviness Asymmetry on Laminate Strength

Abstract

The study of defects and their influence on the performance of composite structures is well documented. However, simplifications are often made regarding the morphology of these defects. As part of the CerTest project, a database of composite features and defects is being built, for which an assessment must be made of what information is relevant. This study looks specifically at out-of-plane waviness and seeks to investigate whether the commonly used severity metrics (e.g. maximum angle) are sufficient to characterize such defects when considering more complex morphologies. To assess this, previously developed numerical methods are used to investigate the tensile and compressive strength of cross-ply and quasi-isotropic laminates. These laminates are seeded with asymmetrical out-of-plane waviness. The numerical results demonstrate that for reliable prediction of the strength reduction caused by out-of-plane waviness, the asymmetry is an important consideration with relative reductions from symmetric to asymmetric wrinkle of up to 50% found within the wrinkles evaluated in this study.