Modeling Analysis of Defect Formation during Thick Laminate Compression Molding Process

Defects such as fiber waviness (marcels) and voids (porosity) are detrimental to the performance of thick laminate composites. The formation and elimination of fiber waviness and voids is investigated in this paper through a process modeling and analysis approach. The process model is constructed by considering the resin flow in a porous media coupled with heat transfer and resin curing kinetics. Fixed grid solution in Eulerian coordinate frame and deforming grid solution in Lagrangian coordinate frame are implemented in order to study various aspects of the process. The process model is used to predict. the distribution of resin pressure, temperature, and curing degree, thus revealing locations where defects are likely to be formed in the final part. The model prediction is validated by correlation with previous manufacturing data. Simulations that indicate defect formation are demonstrated. Modeling results indicate that the through-thickness resin pressure gradient, at the non-contact lid-materials interface, bends the fiber bundles and creates fiber waviness. Strategies to eliminate defects are discussed.