A note on the mechanical characterization of non-homogeneous and graded vulcanized rubbers

Ample experimental evidence exists in the literature suggesting the spatial variation of mechanical properties of vulcanized rubbers. Although standard testing methods are based on the homogeneity assumption for rubber specimens, some researchers used these tests without modification to characterize the non-homogeneous rubbers. Within the framework of non-homogeneous material models, this paper proves the inadequacy of the standard mechanical tests and suggests the full-field measurement of displacement-strain in deformed rubber specimens for an accurate characterization. This view is theoretically illustrated by analyzing the deformation of a non-homogeneous rubber slab in a standard shear test.