Experiments and computational modelling combined to shed light on the reinforcement mechanism in reactive extruded pulp fibres/starch biocomposites

Biodegradable and renewable biocomposites have gained interest as solutions to reduce the environmental impact of composites. In this work, pulp fibres/thermoplastic starch biocomposites were fabricated with a single-step water-assisted reactive extrusion and characterised by thermomechanical analysis. This specific manufacturing process led to a reinforcement mechanism that, through both the upper-bonding theory and traditional simulation methods, cannot be properly captured. We investigated the relevance of the interface in such phenomena through micromechanical simulations performed via full-field representative elementary volume finite elements. The deviation between the experimental and simulated results led to a deepening of the investigation of the reinforcement mechanism at the matrix/fibres interface, where the modelling hypotheses failed to describe the system. This work pioneers a joint effort between modelling and experimentation in the overarching need for theoretical descriptions of outstanding reinforced short fibre polymer composites when the interactions between polymer matrix and reinforcement exceed the ‘perfect’ adhesion of the classical micromechanics.