Finite Element Modelling of the Progressive Damage and Failure of Thermoplastic Polymers in Puncture Impact

This study analyses the response in puncture impact tests of two types of polymers. Though both investigated materials are polyamide based semi-crystalline thermoplastics, at high strain rates, their behaviour differs as one exhibits ductile behaviour while the other brittle failure. As the investigated materials present high strain-rate dependency, they were modelled with the help of elastic-plastic constitutive laws with rate-dependent plasticity; damage was modelled using ductile and shear damage criteria. The stress-strain response at high strain rates (as puncture impact tests determined rates of deformation up to 200 s-1) and the damage parameters (fracture strain as a function of stress triaxiality and shear stress ratio) were determined and calibrated using finite element analysis simulations through a reverse engineering approach. Simulations performed with the calibrated material models described accurate results in terms of puncture force, puncture energy and failure mechanisms for both investigated polymers.