Effect of Displacement Rate on the Mode I Fracture Behavior of Rubber Toughened PMMA

Abstract

Mode I fracture behavior of rubber toughened PMMA(RT-PMMA) was studied over five decades of displacement rates(10^-4-13 m/s)using a high speed tensile testing machine. Two kinds of RT-PMMA, extruded RT-PMMA containing 20 wt.% rubber particles(EM20) and pressed RT-PMMA containing 40 wt.% rubber particles(PM40), exhibited different rate dependencies of the maximum mode I stress intensity factor, K_{I max} and the maximum mode I energy release rate, G_{I max}. K_{I max} and G_{I max} of EM20 decreased rapidly at high rates(1-11m/s). This suggests that the toughening effect due to rubber blending was dramatically reduced at the high rates. PM40, on the other hand, retained high K_{I max} and G_{I max} values at all the rates tested, thus, maintaining the toughening effect even at a rate of up to 13 m/s. Neat PMMA was also examined, for comparison, and its K_{I max} was found to increase with increase in the displacement rates while G_{I max} remained constant. The rate-dependent K_{I max} and G_{I max} values are discussed, taking(K_{I max})²/G_{I max} into account, and the fracture surface morphology of the specimens is also considered.