Micromechanics stiffness upscaling of plant fiber-reinforced composites

Fiber-reinforced green composites made from natural plant fibers are an increasingly popular sustainable alternative to conventional high-performance composite materials. Given the variety of natural fibers themselves, and the even larger variety of possible composites with specific fiber dosage, fiber orientation distribution, fiber length distribution, and fiber–matrix bond characteristics, micromechanics-based modeling is essential for characterizing the macroscopic response of these composites. Herein, an analytical multiscale micromechanics model for elastic homogenization is developed, capable of capturing the variety. The model features (i) a nanoscopic representation of the natural fibers to predict the fiber stiffness from the universal stiffness of the fiber constituents, mainly cellulose, (ii) a spring-interface model to quantify the compliance of the fiber–matrix bond, and (iii) the ability to model any (and any combination of) orientation distribution and aspect ratio distribution. Validation is performed by comparing the predicted stiffness to experimental results for as many as 73 composites available in the literature. Extensive sensitivity analyses quantify the composite stiffening upon increasing fiber volume fraction, fiber alignment, fiber length, and fiber–matrix interface stiffness, respectively.