Micro-mechanism of fatigue crack growth: Comparison between carbon black filled NR and SBR

摘要

The present paper investigates the fatigue crack growth in both crystallisable and non-crystallisable elastomers under relaxing loading conditions. The study focuses on the determination of the mechanism of fatigue crack growth. For this purpose, an original "micro-cutting" method developed in a previous study for carbon black filled natural rubber (NR) is employed to observe microscopic phenomena involved in the growth of the crack during SEM observations. In crystallisable NR, the cavitation induced by the decohesion between oxides and rubber matrix is the major fatigue damage and it generates heterogeneous deformation and ligaments (more crystallized zones which resist to crack propagation). In carbon black filled styrene butadiene rubber (SBR), cavities containing zinc oxides fail when the crack propagates and the heterogeneous deformation only induces filaments which do not resist to crack propagation. Based on SEM observation, a fatigue crack growth mechanism in non-crystallisable SBR is proposed. Results are compared with those obtained with NR.