Simulation and Analysis of Process-Induced Distortions in Hemispherical Thermostamping for Unidirectional Thermoplastic Composites

This work aims at analyzing process-induced distortions (PIDs) for unidirectional thermoplastic composites in the thermoforming process and evaluating the effects of fiber reorientations and stamping-induced stresses. Hemispheres with symmetric and asymmetric lay-ups are manufactured by the thermostamping process. A simulation method of PIDs is developed and a constitutive model is presented to reflect fiber reorientations in thermostamping. Additionally, stamping-induced stresses are embedded in the simulation. Good correlation is obtained between the prediction and experimental results. Regarding hemispheres with the symmetric lay-up [0/90/0/90](S), stamping-induced stresses play a dominant role in PIDs and determine the deformation trend; fiber reorientations contribute approximately 76% to thermal distortions. Stamping-induced stresses could be neglected in the PID prediction for the investigated three different asymmetrical lay-ups, and contributions made by fiber reorientations range from 18% to 28%. Both fiber reorientations and stamping-induced stresses are significant factors for PIDs for unidirectional thermoplastic composites in the thermoforming process. POLYM. COMPOS., 40:1786-1800, 2019. (c) 2018 Society of Plastics Engineers