Estimation of compressive strength in thick continuous fibre composites: Quantifying the role of initial fibre misalignment

The present study investigates the compressive strength of continuous fibre composites. These materials comprise almost ten different fibre/matrix pairs with four epoxy-based thermoset resin systems, three different carbon fibres and three manufacturers. The experimental values obtained from flexural testing on thick laminates (with 10 samples for each pair) are compared to an analytical compressive failure criterion. This latter model incorporates ease of use in engineering design and mechanistic contributions, including material (non-linear shear behaviour of the ply), manufacturing (initial fibre misalignment) and structural effect (loading, neighbourhood of ply). A comparison between the experimental and estimated values, using the standard deviation of the frequency distribution of fibre misalignment, demonstrates a satisfactory or excellent outcome. The comparison for a pair produced less favourable results, with greater discrepancies observed between two different manufacturers. The spatial distribution of fibre misalignment provides evidence that, in certain instances, a single value may be insufficient for accurately characterising the role of defects in compressive failure.