Simulation of Gas and Resin Transport Mechanisms in Manufacturing Process of Composite Structures and Their Effect on Porosity

Porosity, as a manufacturing process-induced defect, highly affects the mechanical properties of cured composites. There are several contributing factors to the formation of porosity in composite structures, most notably entrapped air, bag leaks, and volatiles or off gassing. These sources highlight the multi-scale and multi-physics nature of the formation of porosity which make it such a challenging problem to solve. Understanding how these mechanisms contribute to the formation of porosity becomes a key tool in minimizing their negative effect. Experimental evidences show that local resin pressure history plays a major role in void growth during a cure cycle. Local reductions in resin pressure due to factors such as geometric features or cure shrinkage can lead to growth of existing voids and increase the likelihood of porosity becoming locked into the final part structure. Prediction of local resin pressure has been the focus of this approach to modeling the cure of composite structures. This study is focused on developing an efficient FE modeling framework to simulate the resin pressure and porosity (bubble) formation in a composite part. The case study presented here features a laminate with ply drop-off subjected to compaction pressure via a caul plate.