Constitutive modelling of compressibility induced by damage in carbon black reinforced natural rubber

摘要

While natural rubber is commonly considered as an incompressible material, this study shows how carbon black reinforced natural rubber (NR-CB), when subjected to various mechanical loading conditions (uniaxial, hydrostatic, monotonic, cyclic), is affected by volume change. Experiments show a volume variation even for low straining values and a significant volume change for large elongations. Moreover, the volume change can be either reversible or not, depending on the loading conditions. It is related to a competition between void growth, chain orientation and stress softening. At a microscopic scale, in-situ Scanning Electron Microscopy (SEM) examinations and image analysis allow to record damage and microscopic volume change as a function of elongation. Therefore the volume change measured at the microscopic scale is equal to the macroscopic volume change. Based on the experimental results, this paper shows that the assumption of incompressibility is worth being revisited. Thus, a nearly-compressible approach was considered, where the strain energy is assumed to be the sum of spherical and deviatoric parts which are both affected by damage. The model was then implemented in a finite element code. Good agreement was obtained between experimental results and model predictions.