MODULAR PLATFORM TO MODEL PARALLEL INELASTIC MECHANISMS IN RUBBER-LIKE MATERIALS

Abstract

ABSTRACT Cross-linked rubber-like materials exhibit an elastic behavior with several inelastic features such as the Mullins effect, Payne effect, permanent set, deformation-induced anisotropy, and hysteresis. Although these features are being modeled individually, few attempts have been made toward systematic integration of these models into one model to consider damage accumulation in rubber-like materials. A new platform is presented to couple constitutive models of different inelastic mechanisms into one generalized model that can simultaneously consider them all. The kinematic structure of the proposed approach is based on two concepts: (1) the concept of microsphere and (2) the concept of network decomposition. The polymer matrix is decomposed into a number of parallel networks, in which each network describes one inelastic feature and is represented by one microsphere. Accordingly, the energy of the polymer matrix, $\Psi$, is the summation of the energies of the parallel networks. A network is considered as a three-dimensional (3D) assembly of unidirectional subnetwork elements distributed in all spatial directions represented by one microsphere. Such structural breakdown allows us to simplify different inelastic mechanisms as 3D assemblies of one-dimensional (1D) elements that host simplified 1D inelastic mechanisms. This concept replaces the complex 3D formulations of finite inelasticity based on the multiplicative decomposition of the F by a simple solution that can be further scaled up and integrates other models. The microsphere enables us to derive the stretch and the deformation history for each direction. Modular design of the platform allows models to be replaced anytime. Any ill-performing or expensive model can be later substituted by an improved version or temporarily deactivated. To validate the concept, a platform is proposed that can host models of permanent set, hysteresis, and Mullins effect. The accuracy of the platform is evaluated in comparison with experimental data and with respect to different models.