A sequential approach for simulation of thermoforming and squeeze flow of glass mat thermoplastics

In this study, a sequential thermoforming and squeeze flow simulation approach for Glass Mat Thermoplastic (GMT) material is proposed and applied to a hat section geometry using input properties based upon Tepex flowcore, a long glass fiber reinforced polyamide (PA/GF) mat manufactured by Lanxess. First, a fully-coupled thermomechanical simulation is conducted based on a purely Lagrangian description, to efficiently capture thermoforming. Subsequently, relevant state variables are mapped and initialized for a Coupled-Eulerian-Lagrangian (CEL) approach. The CEL approach is adopted to accurately capture squeeze flow, which is not possible by a purely Lagrangian description. While numerical techniques differ, both approaches use the same three-dimensional and thermomechanical constitutive equations including an equation of state, a nonlinear viscosity model, and crystallization kinetics, implemented through a material user-subroutine (VUMAT) for the commercially available simulation software package ABAQUS/Explicit.