Study of the Behaviour of Non-Crimp Fabric Laminates by 3D Finite Element Model

Abstract

The aerospace industry is committed to improving the performance of aircraft whilst reducing emissions and weight. Part of this goal can be achieved with the use of new types of composite materials, such as non-crimp fabric composites.

These new composites, still under development, are made from dry fabrics and combine in theory the excellent in-plane behaviour of the unidirectional pre-impregnated tape composites with better out-of-plane behaviour and lower cost of the woven fabric composites. In practice, however, due to several parameters associated with the different stages of manufacturing of the non-crimp fabric laminates, some in-plane and out-of-plane waviness at the mesoscopic scale is introduced. This waviness (typically called crimp) is responsible for lowering the in-plane behaviour and causing specific failure models.

A new method to efficiently model the fibre crimp of the tows in mesoscopic scale 3D finite element models of non-crimp fabric laminates is presented in this study. This method consists of modelling the fibre crimp using straight meshes and “rotating” the mechanical properties according to the actual direction of the fibres. In order to ensure the validity of this method, it has been compared with previously developed methods in which the mesh is curved along the fibres direction.

The new method allowed the creation of complex parametric 3D FE models which in turn have been used to predict the apparent in-plane stiffness properties and to study the compressive behaviour and the in-plane shear behaviour of a non-crimp fabric laminate.