Numerical Investigation of the Phase Evolution in Polymer Blends under External Mechanical Loadings

The influences on the development of polymer blend microstructures are not yet fully understood in the manufacturing processes. The purpose of this paper is to give a closer look at the effect of the elastic energy on the decomposition process. The decomposition process of a melt consisting of two polymers with different shear moduli is investigated. Due to the resulting heterogeneous material behavior and deformations, the generated energy field is heterogeneous as well. This energy causes changes in the local stability of the mixture, which yields phases consisting of both the polymers. Additionally, possible large deformations result in dominating diffusion directions

Estimation of the Compression Modulus of a Technical Rubber via Cyclic Volumetric Compression Tests

In many applications for finite element (FE) simulations rubber materials are assumed to be nearly incompressible by applying a high ratio between compression modulus and shear modulus. The compression modulus is commonly given as a constant value in FE analysis. In reality this assumption is not fully correct. Influencing factors like the compressibility of the included filler can lead to a notably change of the compression modulus during mechanical loading. The focus of this work is on the estimation of the cyclic evolution of the compression modulus for a technical ethylene propylene diene rubber (EPDM) by using cyclic volumetric compression tests

A framework to model thermomechanical coupled of fracture and martensite transformation in austenitic microstructures

A fully thermomechanical coupled phase-field (PF) model is presented to investigate the mechanism of austenite-to-martensite phase transformation (MPT) and crack initiation as well as its propagation in pure austenitic microstructures. The latent heat release and absorption involved in the MPT are explicitly taken into account by coupling the PF model with transient latent heat transfer. In order to consider temperature dependency in the PF model for MPT, a temperature-dependent Landau polynomial function, whose parameters are identified using molecular dynamics (MD) simulations, is proposed. Furthermore, the fracture surface energy is approximated based on the second-order PF model and then, the temporal evolution of the damage variable is given by the variational derivative of the total potential free energy of the system with respect to the damage variable. The achieved numerical results demonstrate that the model can be employed to predict the fracture mechanism of austenitic microstructures under a thermomechanical field in a multiphysics environment. The results reveal that the temperature has a tremendous impact on the growth rate of both martensitic variants and consequently on the crack growth path. The key contributions of this work are to shed light on the impact of thermal boundary conditions on the coupled process of MPT, crack initiation and growth