Time-to-failure of randomly reinforced glass strand/urethane matrix composites: data, statistical analysis and theoretical prediction

This article concerns the time-to-failure ("static fatigue") response of randomly reinforced composites. The composites under consideration consist of swirl-mat and chopped glass fiber strands embedded in a urethane matrix, which are candidate materials for application in the automotive industry. The paper proposes a mechanics-based predictive model to relate time-to-failure to the magnitude of applied static loads. The model is based upon concepts of viscoelastic crack growth and utilizes detailed short-time, i.e. less than one day, failure data. Independently of the above model, this article presents a statistical analysis of long-term failure and survival data for the swirl-mat composite under static loads. These data were collected independently for durations of up to one year. Both approaches yield similar results for the relation between stress and failure time. The model is subsequently utilized to predict failure time for the chopped fiber composite material, for which no long-term data are available. (C) 2001 Published by Elsevier Science Ltd.