Plasticity and fracture initiation in rubber‐toughened poly(methyl methacrylate)

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Abstract
The deformation behavior of rubber toughened poly(methylmethacrylate), RT‐PMMA, has been investigated in terms of the ability of the material to nucleate plasticity. Work‐hardening rate parameter K measurements in the early stages of the nonelastic response in a constant strain‐rate test are used to probe the development of micro shear zones as a function of rubber volume fraction. The results reveal the existence of a sharp transition from difficult to easy shear band nucleation for a critical rubber volume fraction Vc. This abrupt change in mechanical behavior also shows in the evolution of the critical stress intensity factor K measured at the onset of crack initiation. These findings are discussed in terms of the morphological parameters of the blends.