Modelling and characterisation of dynamic behaviour of short-fibre-reinforced composites

This study proposes a constitutive model of viscous behaviour of short-fibre reinforced composites (SFRC) with complex distributions of fibre orientations and for a wide range of strain rates. The model is based on an additive decomposition of the state potential for the computation of composite macroscopic behaviour. Thus, the composite material is seen as the assembly of a matrix medium and several linear elastic fibre media. The division of short fibres into several families means that complex distributions of orientation or random orientation can be easily modelled. The matrix behaviour is strain-rate sensitive, i.e. viscoelastic and/or viscoplastic. Viscoelastic constitutive laws are based on a generalised linear Maxwell model and the modelling of the viscoplasticity is based on an overstress approach. The accuracy of the model is assessed for the case of polypropylene reinforced with short glass fibres. Matrix material parameters are identified from experimental tests carried out at several loading rates. Distributions of fibre orientation are characterised by micro-computed tomography. Comparisons between numerical and experimental responses in different loading directions and under different strain rates demonstrate the efficiency of the model.