Prediction of in-plane stiffness properties of non-crimp fabric laminates by means of 3D finite element analysis

Non-crimp fabric (NCF) composites are constituted by differently oriented layers of ideally unidirectional fibre tows. However, a slight waviness always appears in the tows. The applicability of the general laminate theory (GLT) to obtain the stiffness properties of NCF laminates is elucidated in this paper. For this purpose, a 3D finite element (FE) model of the representative unit cell (RUC) of a single NCF lamina has been carried out to obtain its apparent stiffness properties, which are employed, along with the GLT, to determine the stiffness properties of the laminate. These properties are compared with those obtained from the FE model of the RUC of the whole laminate for several configurations with different stacking sequences, fibre contents and crimp angles. Finally, predictions are compared with existing experimental results. The numerical results achieved validate the use of the GLT in NCF composites, once the lamina properties have been calculated taking into account the internal structure of these materials.