Velocity jump in the crack propagation induced on a semi-crystalline polymer sheet by constant-speed stretching

Abstract

It has long been known for elastomers that the velocity of crack propagation jumps as a function of strain. On the other hand, such a jump has not been reported in the literature for polymers which do not exhibit a rubbery plateau in the storage-modulus plot. Here, we report observation of jumps in crack propagation for semi-crystalline polymer sheets without the rubbery plateau, as a result of pulling the sheets at a constant speed. We discuss the advantages of this crack-propagation test under constant-speed stretching and provide physical interpretation of the velocity jump observed for non-elastomer sheets on the basis of a recently proposed theory for the velocity jump in crack propagation.

Crack propagation under static and dynamic boundary conditions

“…Considering that the velocity jump has been utilized effectively for developing tough elastomers in the industry, the results of the present study are useful for developing tough polymers in general. This is especially because the previous study [5] suggests theoretically that the velocity jump is expected be observed universally for variety of materials and the previous studies [9] and [8] demonstrate experimentally that the dynamic test is more sensitive for detecting the velocity jump.…”

“…Recently, it is reported that the velocity jump is not observed for a semi-crystalline polymer [8] as a result of performing the crack-propagation test under the static boundary condition. However, more recently, the velocity jump is successfully observed for the same semi-crystalline polymer when the crack-propagation test is performed under a dynamic boundary condition [9].…”