Parameter identification methods for visco- and hyperelastic material models

Abstract

Many materials in modern civil engineering applications, such as interlayers for laminated safety glass, are polymer-based. These materials are showing distinct viscoelastic (strain-rate) and temperature dependent behaviour. In literature, different mathematical representations of these phenomena exist. A common one is the ‘Prony-series’ representation, which is implemented in many state-of-the-art Finite-Element-Analysis-Software to incorporate linear viscoelastic material behaviour. The Prony-parameters at a certain reference temperature can either be determined by relaxation or retardation experiments in the time domain or with a steady state oscillation in the frequency domain in the so called ‘Dynamic Mechanical Thermal Analysis’ followed by a ‘Time–Temperature-Superposition-Principle’. However, present research shows that polymeric materials also may need to have constitutive equations which include hyperelasticity (nonlinear stress–strain behaviour in a quasi-static condition) when undergoing large deformations, so that the material model should be expanded for a more realistic representation in numerical simulations. A novel method for the whole identification process for a numerical material model in terms of a linear Generalized Maxwell Model (Prony-series) based on experimental data will be presented. Furthermore, material parameters for different hyperelastic material models based on experimental investigations will be shown and compared. Future research activities as well as extensions of the presented novel method are also highlighted within this paper.