Photoelastic Stress and thermographic measurements of automotive windscreen defects generated by projectile impact

Abstract

This paper describes an experimental technique to evaluate the stress distribution around an automotive windscreen ‘chip’, that is created by projectile impact. This stress distribution is measured before and after a typical resin injection repair procedure and the results indicate a significant reduction in the residual shear stress. Concurrent thermographic measurements of the impact region during the repair procedure also suggest that the quality of the repair is dependent on the temperature profile at the time of repair. Preliminary computational modelling of a representative windscreen defect illustrates the predisposition of ‘star-shaped’ chips to crack-off to a windscreen edge under typical vehicle usage.