Study on the impact of fibre wrinkle on the compression of composite laminates

Fibre wrinkle is an unavoidable manufacturing defect of fibre reinforced composites, which leads to a significant decrease in the mechanical properties, especially in the compressive strength of composite laminates. It is very important to study the effect of fibre wrinkle on compression failure for quantitative evaluation of compressive strength of composite materials. In this paper, the correlation between wrinkle characteristic parameters and compression failure was studied by numerical and experimental analysis. MATLAB and Python scripts were used to create the geometric model with controllable wrinkle geometry in ABAQUS. The damage model with multi-damage mode such as fibre kinking, matrix damage and delamination was established. The effects of fibre wrinkle parameters on compression failure mode and compressive strength of unidirectional and multidirectional laminates were analyzed based on the damage model. The results show that the dominant failure mode changes from fibre kinking to delamination with the increase of wrinkle severity, for either unidirectional or multidirectional laminates. For the unidirectional laminates studied, the threshold of fibre wrinkle angle for failure mode shift lies between 4° and 6°, while that for multidirectional laminates is between 8° and 9°. There exist sensitive and non-sensitive zones for the influence of fibre wrinkle angle and wrinkle area height ratio on compressive strength of unidirectional laminates. When there are multiple wrinkle areas in the cross-section of laminates, delamination does not necessarily occur in the most severely wrinkle area. For maximum ply wrinkle angle greater than 45^o, delamination is less likely to occur because the peak longitudinal stresses carried by the ply decrease due to ply instability, resulting in a weak interlaminar shearing.