Experimental determination of failure strength in automotive windscreens using acoustic emission and fractography

摘要

This paper presents a methodology to determine failure stresses from components consisting of laminated safety glass. For this purpose, automotive windscreens were tested under quasi-static loading by a head impactor for pedestrian protection. Automotive windscreens consist of two glass ply connected by a polyvinyl butyral interlayer. During the experiment, the failure origin was determined by acoustic emission localisation. The computed failure origins were examined for fracture marks, particularly for the fracture mirror. Fracture mirrors have a direct relation to failure stresses by a material constant, which can be used to determine the failure stresses of brittle materials. It is shown, that the measured stress samples fit best to a two parameter Weibull distribution. The experimentally obtained failure stresses are compared to numerical results obtained by finite element analysis. Furthermore, observations on fracture marks confirm the conclusion, that the glass ply both failed at the interior side. It could also be shown, that in eleven of twenty experiments, the interior ply failed first. With the gained failure stresses and the fracture toughness, conclusions were drawn for critical flaw sizes and their statistical distribution.