Strain-Amplitude and Strain-Rate Dependent Craze Damage of Poly(Methyl Methacrylate)

Abstract

Dynamic mechanical analysis tests and quasi-static tensile tests were conducted on polymethyl methacrylate (PMMA). Craze damage images on PMMA samples' surface were acquired by using an optical microscope. Evolution of the crazing damage was investigated. The results suggest that crazing is loading rate and strain-amplitude dependent. In dynamic mechanical tests, the craze damage becomes more and more serious with the increase in strain amplitude, resulting in the Payne effect. Under quasi-static loading, there is a critical strain over which the surface crazes become visible; the greater the loading rate, the greater the critical strain. Moreover, stretching at different rates leads to difference to the morphology of crazes. The surface crazes stressed at lower loading rate are longer and more fully developed than those at higher loading rates, which results in a faster decline in static elastic modulus.