THERMAL AND IMPACT-INDUCED STRESS FAILURE IN PAINTED TPO - THE ROLE OF SURFACE-MORPHOLOGY

With the introduction of new plastic substrates such as thermoplastic olefins, there is a need to establish a reliable baseline knowledge on stone impact response characteristics under a variety of impact condi tions, coating types, coating application conditions, substrate proces sing, and surface pretreatment conditions. Dynamic mechanical properti es of engineering plastics and polymeric coatings are strong functions of the temperature and strain rate which affect impact response. In i njection molded plastics, morphology, crystallinity, composition, and in-plane stresses at the surface can significantly differ from those o bserved in the bulk. In injection molded TPO layered surfaces, structu res exist which consist of varying crystallinities of cohesively weak polypropylene and rubber. Based on the morphological complexity of the TPO substrate, stone impact response of a painted TPO surface is a co mplex phenomenon. This work is to present an approach, via numerical s imulation based on a physical model developed in our laboratories, to predict the locus of failure within TPO due to stone impact.