Application of a Discrete Mesoscopic Finite Element Approach to Investigate the Bending and Folding of Fiber-Reinforced Composite Materials during the Manufacturing Process

During the manufacturing of fabric-reinforced composite parts using a matched-die compression molding process or liquid composite molding, the fabric may experience local in-plane compressive loads that cause out-of-plane deformations. The waves that result from this outofplane motion can lead to the formation of resin rich pockets (during the infusion stage of a dry fabric) or they may be forced down into a fold by the tooling. Defects such as resin-rich pockets and folds compromise the structural integrity of the formed composite part. Therefore, it is valuable to have a simulation tool that can accurately capture the fabric bending properties and predict the locations where waves or folds are likely to occur as a result of the manufacturing process. The tool can then be used to investigate changes in the forming parameters such that the development of such defects can be mitigated. A hybrid finite element model used with a discrete mesoscopic approach captures the behavior of continuous fiber-reinforced fabrics where the fabric yarn is represented by beam elements and the shear behavior is implemented in shell elements. User-defined material subroutines describe the mechanical behavior of the beams and shells for their respective contributions to the overall fabric behavior. Simulations are used to demonstrate the ability of the modeling approach to predict the amplitude and curvature of out-of-plane waves. The simulation results are compared with experimental data to show the accuracy of the modeling. Additional models are presented to demonstrate the capability of the simulation tool to capture fabric folding.