Notched Strength of Thermoplastic Woven Fabric Composites

Abstract

Woven fabric composites with a thermoplastic matrix form a class of promising materials for industrial use, due to their balance of properties. They combine excellent mechanical performance with ease of processing. Failure behavior of notched woven fabric composites shows a number of peculiarities, the most notorious being the dependence of notched tensile strength on notch radius below a certain hole size. This dependence, which is observed for all fiber reinforced composites, has been modelled by other authors with the aid of semi-empirical continuum mechanics models. If at all based on physical principles, the modelled fracture process rarely coincides with experimentally observed failure phenomena. This study investigates failure of notched woven fabric (0-90)4, E-glass laminates with a PETP matrix. A model is proposed which is, unlike other previous modelling efforts, related to experimentally observed fracture phenomena. It introduces the ineffective length of a critical element in the notch root, obtained by a simple shear lag-type analysis. The notched strength is shown to depend on the ratio of notch radius to the critical element ineffective length. The model is able to predict changes in notched strength with composite parameters like fiber volume fraction, fiber bundle diameter and interfacial or matrix shear strength, and takes into account the composite microstructure.