Multi-directional hybrid laminates-studying the effect of fragmentation and dispersed delamination on stress-strain curves of unnotched laminates using analytical modelling.

Hybridisation is one of the approaches to introduce pseudo-ductility to brittle composite materials. In this approach, two or more different types of fibre are combined and if the configuration and material constituents are well selected, the tensile response shows a gradual failure and pseudo-ductile strain. Different types of hybrid composites with continuous layers have been studied to produce pseudoductile tensile behaviour. However, most hybrid material studies to date have been focused on Uni- Directional (UD) laminates which are not usually applied in industry due to poor transverse mechanical properties.

In this study, the behaviour of multi-directional hybrid laminates made with UD hybrid sub-laminates is studied. The final goal is to introduce pseudo-ductility to layups with wider industrial applications. The effect of layup as well as the UD building-block stress-strain curve on the final stress-strain curve of the laminate is also studied.

A new analytical approach based on Classical Laminate Theory is introduced in which the effect of different damage modes in UD hybrid laminates (fragmentation and dispersed delamination) is taken into account. The output of this method is the non-linear stress-strain curve of a multi-directional laminate with UD hybrid sub-laminates. This method is then used to study the effect of different parameters such as the mechanical properties of the constituents (low and high strain materials) and layup on the pseudo-ductility.