Identification of Material Parameters for Damage Model of Ductile Failure in Thermoplastic Polymers

Abstract

In recent years, polymer nano-composites (PNCs) have increasingly gained more attention due to their improved mechanical, barrier, and thermal as well as optical, electrical, and biodegradable properties in comparison with the conventional microcomposites or pristine polymer . Although PNCs offer enormous opportunities to design novel material systems, development of an effective numerical modeling approach to predict their properties based on the complex multi-phase and multiscale structure of these composites is still at an early stage. Authors recently developed a multiscale computational framework to predict the mechanical properties of PNC [2]. Upon the large deformation, fiber debonding occurs due to the significant difference between the properties of inclusion and the host polymer in polymer nanocomposite.The finite element model of fiber debonding in nano-reinforced composite has been developed based on the cohesive-zone model of the interface [3]. Matrix cracking is another failure mechanism in composite materials. Thermoplastic polymer undergoes large ductile deformation before losing all load-carrying capacity. The loss of load-carrying capacity results in the progressive degradation of material stiffness. In this paper the modified Gurson-Tvegaard- Needleman (GTN) model was applied to thermoplastic polymer (here high-density polyethylene) to model its plasticity and damage behavior. GTN material parameters and elastic and hardening parameters has been obtained using experimental results (tensile and shear tests, Digital Image Correlation). This technique can be applied to other materials and it is not limited to thermoplastic polymers.