Predicting the Strength and Failure Envelops of High-Performance Discontinuous Composites

Abstract

Carbon–fibre tow–based discontinuous composites are novel materials combining the high–performance of carbon–fibres with the manufacturability of metals. These composites are reinforced by a network of discontinuous and randomly– oriented fibre–tows (each composed of thousands of aligned fibres), creating a multiscale and unstructured architecture. Consequently, they can be moulded into complex 3D shapes using fully automated and high–rate processes, which makes them suitable for mass–production applications. Moreover, tow–based discontinuous composites can achieve fibre contents up to 60% in volume, and a stiffness similar to that of quasi-isotropic continuous composites. While the complex and multiscale microstructure of tow–based discontinuous composites is key for their manufacturability and good mechanical performance, it also creates a challenge for predicting their properties. This work therefore proposes a multi-scale model to predict the strength and failure envelopes of tow– based discontinuous composites, using the mechanical properties of the tows and their geometry as inputs. The model predicts full failure envelopes for any tension–tension or tension– shear in-plane stress state in less than 5 min, making the model suitable for design of structural components under complex stress states. The model is also able to predict the effect of changing the properties and geometry of the tows on the overall response of the composite, and can therefore be used to design optimal material configurations with improved performance.