Effects of pressure, boundary conditions, and cutting reliefs on thermo-hydroforming of fiber-reinforced thermoplastic composite helmet based on numerical optimization

Compared with layup techniques, thermo-hydroforming is shown to be a viable process for mass production of thermoplastic composite structures due to its relatively rapid cycle time and low impact on the microstructure of the material. However, unlike layup technique, thermo-hydroforming can produce wrinkles in the formed part. A research was conducted wherein ABAQUS/CAE (6.14-1) was employed to numerically study the impact of thermo-hydroforming process parameters on the formation of wrinkles in a thermoplastic helmet. The optimized properties of the fiber-reinforced polymer composite was previously determined by the authors using the preferred fiber orientation model implemented as a user material subroutine (VUMAT). To account for the interaction between different layers of the laminated composite, the cohesive zone model was employed. The objective of the study was to use the simulation tool to minimize the overall wrinkle density and wrinkle height in the formed helmet as a function of the fluid pressure, boundary conditions, and especially the blank shape and the relief cuts made in the blank.