Viscoelasticity of rubber-toughened poly(methyl methacrylate). Part II: Fracture behavior

The fracture behavior of a rubber toughened poly(methyl methacrylate) has been studied at several times and temperatures, using SE(B) and SE(T) testing geometries. Schapery's local approach to fracture in polymers has been used to interpret the results. The theory, originally formulated for fracture of linearly viscoelastic materials, has been modified to account for the non-linear behavior exhibited by the material at higher temperatures. It has been shown that the stress intensity factor at initiation substantially decreases with time and temperature, while fracture energy at initiation, 2F, is constant, in the range explored. As for propagation, the stress intensity factor increases with crack speed. The time-temperature equivalence has been successfully applied, and stress intensity factor master curves for both fracture initiation and propagation have been derived. Predictions made using Schapery's theory agree well with experimental data.