Observation of crack growth in PMMA with a low short glass fibre content by optical interferometry

In order to investigate the effect of short glass fibre on crack growth, th e crack tip was observed using double-cantilever beam samples machined from injection-moulded PMMA plates with a low short glass fibre content by mean s of optical interferometry. It was shown that the interference fringes wer e distorted around the fibre crossing the crack planes over a region two to four times larger than the fibre diameter, and that the fibre depressed th e crack opening due to bridging between the crack planes, thus shortening t he craze zone length in front of the crack tip and reducing the crack growt h rate, leaving the arrest line on the fracture surface. (C) 1998 Kluwer Ac ademic Publishers.