Constitutive model to predict the viscoplastic behaviour of natural fibres based composites

The mechanical behaviour of traditional composites is usually assumed as linear-elastic up to failure. However, composites based on natural fibres are characterized by non-linear elasticity, viscous effects and plastic strains before failure. This study presents a rheological model to predict the viscoplastic behaviour of natural fibres based composites. The model was calibrated using a stress-strain curve and two relaxation tests for three different composites reinforced with flax, jute and cotton fibres. The model predicted successfully the behaviour of biocomposites loaded at different strain rates.