On the interaction of internal cracks in polymethyl methacrylate

摘要

Toughening of a brittle matrix can be achieved hrough a number of microstructural mechanisms, :ither by impending crack propagation or by hielding the crack tip from the far field applied tress. The o major mechanisms of crack front lerturbation [1] include crack deflection, crack plane wisting, and crack bowing. These mechanisms are, Lowever, relatively ineffective as sources of toughen-ng because of the non-cumulative nature of these irocesses during the main crack extension. The hielding mechanisms [2] include plastic yielding, nicrocracking, dilatational phase transformations hat occur in the frontal-wake zone, fibre and ductile ihase bridging, and grain bridging and interlocking hat occur in the bridged crack interface behind the rack tip. Because of their cumulative nature during lie extension of the main crack, the shielding aechanisms are more effective in toughening brittle lattices and give rise to fracture resistant curve ehaviour.