Investigation of time dependence of dissipation and strain induced crystallization in natural rubber under cyclic and impact loading

Strain Induced Crystallization (SIC) is one of the special features of Natural Rubber (NR), responsible for its outstanding mechanical performance. Especially, for the short term behavior of NR, e.g. within a rolling tire, the kinetics of SIC plays an important role. SIC can be observed to some extend by thermography, but it is not directly possible to separate the heating effects accompanying SIC from dissipative heating of the rubber material (LeCam et al., 2015, Spratte et al., 2017). By means of synchrotron x-ray diffraction, SIC can be monitored during deformation including cyclic deformations and impact loading with a time resolution of less than 10 ms (Bruning et al., 2013). Combining this method with thermography enables the separation of processes of structure formation and dissipation. This can serve as a basis for a more realistic modelling of the dynamic and thermomechanical behavior of natural rubber. Within the presentation we report about investigations of cyclic loadings of differently Carbon Black (CB) filled NR samples with respect to SIC, melting of the crystallites as well as the dissipative heating and convective cooling of the rubber materials.