Investigation of process-induced deformation in thermoplastic composites through sequential thermoforming simulation considering crystallization kinetics

Abstract

This study presents a predictive method for process-induced deformation (PID) and residual stress in a V-shaped carbon fiber reinforced thermoplastic composite (CFRTP) using sequential thermoforming simulations within integrated thermo-mechanical simulation framework implemented in ABAQUS with user-defined materials subroutine (UMAT). The FE-based thermoforming simulation incorporates theoretical models to consider crystallization effects and the mechanical behavior of CFRTP composite. The thermoforming process, consisting of forming, holding, and demolding stages, is analyzed in detail with respect to temperature distribution, residual stress evolution, and PID. A primary finding was that 1) the CFRTP deformed into a V-shape during forming, 2) residual stress was accumulated due to mechanical constraints in the holding stage, and 3) PID occurred upon demolding, resulting in a spring-in angle of 6.6°. This proposed methodology integrates multiple thermoforming simulations within integrated thermo-mechanical simulation framework, significantly improving computational efficiency and enabling rapid and precise prediction of effective material properties. By minimizing simulation complexity, it provides a practical tool for optimizing CFRTP-based structural and mold designs, reducing shape distortion, and enhancing the dimensional precision of thermoformed composite structures.