LOADING RATE DEPENDENCE OF THE DEFORMATION AND FRACTURE MECHANISMS INIMPACT MODIFIED POLY(METHYL METHACRYLATE)

The tensile and fracture properties of rubber toughened poly(methylmet hacrylate) (rtPMMA) modified by spherical core-shell particles, and po ly(urethane)/poly(methyl methacrylate) (PU/PMMA) interpenetrating poly mer networks (IPN) are investigated at different strain rates. The def ormation and fracture mechanisms are studied by transmission electron microscopy (TEM). The results of the tensile tests show that deformati on in both rtPMMA and IPN involves cavitation. The amount of cavitatio n increases with the strain rate in both kinds of material. This leads to similar mechanical properties in each case, and shows that a spher ical particle morphology is not prerequisite for cavitation. A phenome nological model of the micromechanisms of deformation in core-shell pa rticle modified PMMA is proposed.