Effect of displacement rate on the mode I fracture behavior of rubber toughened PMMA

Mode I fracture behavior of rubber toughened PMMA (RT-PMMA) was studied ove r five decades of displacement rates (10(-4)-13 m/s) using a high speed ten sile 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-1max, and the maximum mode I energy release r ate, G(1max). K-1max and G(1max) of EM20 decreased rapidly at high rates (1 -11 m/s). This suggests that the toughening effect due to rubber blending w as dramatically reduced at the high rates. PM40, on the other hand, retaine d high K-1max and G(1max) 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 e xamined, for comparison, and its K-1max was found to increase with increase in the displacement rates while Gl,a, remained constant. The rate-dependen t K-1max and G(1max) values are discussed, taking (K-1max)(2)/G(1max) into account, and the fracture surface morphology of the specimens is also consi dered.