Literature Review and Finite Element Study of Fibre Damaged CFRP laminates in Compression

This work is a direct continuation of (Magnani 2020) who investigated the effects of fibre cuts on the compressive strength of CFRP laminates. The previous study experimentally found that fibre damage reduces compressive strength regardless of damage configuration. In addition, Magnani proposed a FR model which appeared to be in agreement with his experimental findings. The original objective of this work was to reproduce the proposed finite element model in order to perform a parametric study. However, the model was proven to be unsuitable and when its shortcomings were corrected, no strength reduction was found from fibre cuts. Additional models in agreement with the established literature were developed. A literature review of experimental and numerical investigations into fibre damage in CFRP compression was conducted and found evidence suggesting that fibre cuts have minimal impact on the compressive strength of CFRP laminates, in complete contradiction with the experimental findings in (Magnani 2020). The observations made by Magnani do however appear to match well with investigations of fibre kinking and microbuckling. The proposed explanation for this is a failure in experimental methodology which filed the gaps in fibre cracks with resin without properly opening the cracks with the required tensile preload. This meant that, as the coupons were compressed, the fibre crack fronts entered matrix instead of butting into each other. The plastic deformation from the low yield polymer as the fibres penetrate this region would have induced unrealistically large distortion of fibres. This made the tested coupons behave as though they contained extremely large fibre misalignments induced by the gratuitous presence of matrix whose plastic deformation twisted the fibres out of alignment. This is in contrast with the fibre damage one would expect in real circumstances which would invariably crack the weaker matrix as well.