Fracture Testing of Brittle Polymers

Abstract

Three optical methods will be presented which, together with adequate measuring devices of short time physics, are powerful tools in the investigation of relevant fracture parameters during crack propagation. By reflection optics, crack speeds can be measured in a very large range. By microscopic optical interferometry, the size and shape of the craze zone at the crack tip and the crack opening can be determined thus leading to an insight into the micromechanics in the crack tip region. By the shadow optical method of caustics, information on the stress field around the crack tip is used in the determination of stress-intensity factors. The methods are applied to fracture induced by different types of loading such as quasistatic, fatigue and impact. For PMMA, life times measured in creep rupture will be compared with the fracture mechanics approach. Critical craze dimensions of PMMA measured during crack propagation will be given and results of the micromechanics of fatigue crack propagation in PMMA and PVC will be presented. For dynamic loading some recent results will be reviewed.KeywordsStress Intensity FactorFatigue Crack PropagationCrack Propagation RateDynamic Stress Intensity FactorCrack SpeedThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.