Damage and fatigue in cross-linked rubbers.

摘要

Damage and fatigue of elastomers have not been fundamentally understood because of the complex nature of these materials. All currently existing models are completely phenomenological. Therefore two problems have been investigated in this research to address those fundamental issues. The first problem was creating an innovative concept with a mathematical modeling, which would be able to describe the damage using molecular characteristics of elastomers. The second problem is developing new approaches to study fatigue, and especially impact fatigue of elastomers.;The following results have been obtained in this research.;A theoretical model of damage has been developed which involves the basic molecular characteristics of cross-linked elastomers and takes into account the effects of viscoelasticity and stress-induced crystallization.;This model was found very reliable and successful in description of numerous quasi-static simple extension experiments for monotonous and repeating loadings. It also roughly predicts in molecular terms the failure of elastomers with various degrees of cross-linking.;Quasi-impact fatigue tests with different geometry of an indenter have also been performed. Some microscopic features of rubber damage have been investigated using optical microscopy and SEM. In particular, the accumulation of a completely de-vulcanized, liquid-like substance was observed under intense, multi-cycle impacts. All the findings discovered in quasi-impact experiments are consistent with the damage model predictions.