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, KI max and the maximum mode I energy release rate, GI max. KI max and GI 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 KI max and GI 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 KI max was found to increase with increase in the displacement rates while GI max remained constant. The rate-dependent KI max and GI max values are discussed, taking(KI max)2/GI max into account, and the fracture surface morphology of the specimens is also considered.