Influence of distributed out-of-plane waviness defects on the mechanical behavior of CFRP laminates

One of the most common defects induced during manufacturing of laminates is out-of-plane fibre waviness. This defect significantly affects the mechanical behavior of the laminate and reduces fatigue life and the load capacity of the material. Therefore, it is important to understand the impact of fibre waviness on the performance of composite laminates. In this work, multiple out-of-plane waves have been introduced throughout a Carbon Fibre Reinforced Polymer (CFRP) laminate at different thickness positions. The specimens were tested under tensile loading and an analysis of the surface of the laminate has been carried out by means of Digital Image Correlation (DIC). The results obtained by DIC were able to predict the apparent strain of the laminate quite accurately, as well as locate up to seven undulations at different depths. It was proved that a laminate with multiple wrinkles has 16% less tensile load strength. The results were used to validate different Finite Element (FE) models of the laminate showing a good agreement. These simple models were able to predict the initiation and propagation of failure in both the matrix and the fibre.