Study of the microstructure evolution caused by the strain‐induced crystallization in polymers

Abstract

AbstractThe strain‐induced crystallization (SIC) in polymers, such as in natural rubber, is a phenomenon manifesting itself as the natural reinforcement caused by the high deformation. Experimental data obtained from tensile tests show that the crystallization starts at a strain of 200‐400%, whereas, at maximum possible stretches of up to 700%, the volume fraction of the crystallinity reaches its highest degree. The growth and reduction of the crystalline regions cause a hysteresis in the stress‐stretch curve which indicates that the process has a dissipative character. In our work, the described material behavior is simulated by a micromechanical continuum model which involves the degree of network regularity as an internal variable. The focus is on the formulation of the dissipation potential simulating the change of the crystallinity degree during cyclic loading. The current approach furthermore simulates the dependence of the crystal orientation and form on the applied external load, which is achieved by assuming a specific coupling condition between the inelastic deformations and network regularity.