Crack growth mechanism of natural rubber under fatigue loading studied by a real-time crack tip morphology monitoring method
The present paper deals with the crack growth behavior of vulcanized natural rubber under fatigue loading. Our research focuses on the crack tip morphology evolution and its relationship with the crack growth rate. For this purpose, an original real-time monitoring method is applied to capture the crack tip morphology during standard fatigue testing. This method involves the use of a high speed microscopic camera and a dynamic mechanical analyzer with a crack growth testing unit. The tear energy (T) dependence of the crack tip morphology is discussed. It is revealed that there are two characteristic cracking morphologies: at T < 600 J m−2, the power law slope of dc/dn versus T is 6. Surface buckling and peeling at the crack-front surface occur, which result in the appearance of secondary cracks; at T > 600 J m−2, the power law slope of dc/dn versus T is 2. A ligament break-up mechanism dominates. This work gives us new opportunities to study the crack growth mechanism of rubbers from the viewpoint of real-time crack tip morphology investigation.