Interface and micromechanical characterization of tensile strength of biobased composites from polypropylene and henequen strands

The contribution of a reinforcement to the tensile strength of a composite can be evaluated by different micromechanics models. Nonetheless, one of the main difficulties is the evaluation of the intrinsic properties of the reinforcements. The literature shows experimental and model-based methodologies to estimate such intrinsic properties, and few are based on single fiber tensile test in combination with a Weibull analysis. This paper proposes using henequen strand to prepare polypropylene-based composites. Henequen fibers show a high cellulose content that allows obtaining strong interfaces when a coupling agent is added to the composite formulation. The novelty of this work is based on a simplified methodology to evaluate the intrinsic tensile strength of the reinforcements and its contribution to the tensile strength of the composite. A percentage of coupling agent that returns the highest tensile strength is identified with a strong interface. Then, typical values for a coupling factor and interfacial shear strength are used with a modified rule of mixtures and a modified Kelly and Tyson models to obtain the orientation factors. The prediction of composite behavior from fiber properties is necessary to anticipate the correlation between experimental and the back-calculated parameters.