Improved dimensional infidelity of curve-shaped VARTM composite laminates using a multi-stage curing technique – Experiments and modeling

The spring-in phenomenon is a common dimensional infidelity problem that occurs when a curved composite part is released from the mold after full consolidation during a Vacuum Assisted Resin Transfer (VARTM) process. In this study, a multi-stage curing (MSC) technique, which is a typical resolution to cure thick composite parts, is applied to the parts manufactured via VARTM for investigating the induced improvement in the spring-in problem. The experimental results evidently show that the MSC technique significantly mitigates the spring-in problem. A new MSC spring-in model that accounts for the slipping effect between the stage-laminates of each curing stage is also developed for predicting the spring-in behavior during the MSC process. The predictions show a good agreement with the experimental results and suggest that the MSC technique would be a useful method for controlling the spring-in of composite parts.