On the elastic behavior of scission materials

Constitutive equations have recently been developed which account for changes in the mechanical response of an elastomer due to changes in its macromolecular structure. The changes consist of scission of macromolecular network junctions, recoiling of macromolecules and their subsequent cross linking to form new networks with new stress-free reference configurations. This work discusses changes caused by large deformations. For each deformation history, there is a range of deformations in which the microstructure is fixed, with no further scission or cross linking. The elastomer has a modified elastic behavior and a new stress-free reference configuration. The constitutive equation for this post-scission elastic range is developed. Two subclasses of this constitutive equation are defined: Mooney-Rivlin based and neo-Hookean based scission materials. The strain energy density function for each subclass is derived. It is shown how the new material symmetry is determined from the preceding deformation history and the scission and cross linking processes. The effect of scission on the stability behavior of a neo-Hookean based scission material is discussed and a cube under triaxial load is considered.