Mullins effect in filled elastomers characterized by stretching measurements in various geometries

It is well known that the filled elastomers exhibit the considerable degrees of stress-softening in the cyclic stretching tests (L. Mullins, 1947). The Mullins effect is closely related to the energy loss of filled elastomers subjected to cyclic deformation, and its full understanding is very important for the design of rubber products. Interestingly, the emergence of such stress softening is not limited to filled elastomers, and the similar phenomena including cyclic hardening are observed for both soft materials, such as polymer composites, biopolymer hydrogels or tissues, and hard materials, such as shape-memory alloys (K. M. Schmoller et al., 2013).
In the present study (Soft Matter, 2017, 13, 1966–1977), Mullins effect is investigated by two types of biaxial stretching, i.e., equibiaxial and planar extension, and uniaxial stretching for silica-filled SBR (styrene butadiene rubber) with various silica contents. We reveal the effects of the stretching type, the magnitude of strain, the content of filler, filler-polymer interaction and stretching speed on the energy dissipation during cyclic loading.