Influence of manufacturing-induced defects on the fatigue performances of autoclave moulded laminates

In the present work, cross-ply and multidirectional laminates were produced by autoclave moulding. Changes in the process parameters led to different microstructural features in terms of fibre volume fraction, global void content, and void size. Fatigue tests revealed a strong influence of the microstructure on the long-term performances of the laminates, in terms of life to crack initiation, crack propagation, crack density evolution and associated stiffness drop. A criterion recently proposed by the authors to predict the formation of the first fatigue cracks accounting for the actual material microstructure, including voids, was then validated on the new experimental data. The results show the need to properly account for the manufacturing induced defects for a more efficient and safer design of composite parts, and remark the necessity of developing models that link manufacturing process parameters, micro-scale morphology, and mechanical performances to enable a cost-effective production that maximizes the performance/cost ratio.