Consolidation-driven defect generation in thick composite parts

Fibre waviness is one of the most significant defects that occurs in composites, due to the severe knockdown in mechanical properties that it causes. This paper investigates the mechanisms for the generation of fibre path defects during processing of composites pre-preg materials and proposes new predictive numerical models. A key focus of the work was on thick sections, where consolidation of the ply stack leads to out of plane ply movement. This deformation can either directly lead to fibre waviness or can cause excess fibre length in a ply, that in turn leads to the formation of wrinkles. The novel predictive model, built on extensive characterization of pre- pregs in small scale compaction tests, was implemented in the finite element software Abaqus as a bespoke user-defined material. A number of industrially relevant case studies were investigated to demonstrate the formation of defects in typical component features. The validated numerical model was used to extend the understanding gained from manufacturing trials, to isolate the influence of various material, geometric and process parameters on defect formation.