Experimental determination of the rigidity modulus of PMMA near a running crack tip

Abstract

A new method is presented to estimate dynamic rigidity in a quasimicroscopic area at a corack front propagating in PMMA at high speed. This method employed ultrasonic shear waves at MHz frequencies to deviate cracks and to produce marks on the fracture surfaces, and also a relation between the mark depth and the rigidity obtained from formulas of elastic waves and fracture mechanics. It was concluded that no appreciable softening can occur near the running craze tip of PMMA. In addition, growth of crazes and cracks in ultrasonically modulated stress fields is discussed.