Effect of tapered natural fiber on elastic properties of sisal fiber-reinforced composite: An experimental and micromechanics approach

Abstract

In the characterization of natural fiber-reinforced composites, it is crucial to consider the nonuniform cross-section of fibers extracted from plants or leaves, which results from the inherent variation in fiber diameter. This variation is a key aspect of the actual reinforcement behavior, and disregarding it by assuming a uniform cross-section can violate the physical understanding of the composite’s mechanics. This study focuses on characterizing the elastic properties of a natural tapered sisal fiber-reinforced epoxy composite, taking into account the variation in fiber diameter along its length. To achieve this, both experimental, analytical, and micromechanics methods are employed. The experimental approach involves conducting tests to measure the mechanical properties of the composite, while the micromechanics analysis provides a framework to understand the reinforcement behavior and predict the composite’s mechanical response. The study aims to identify and present various elastic properties of the composite, including the longitudinal modulus, transverse modulus, in-plane and out-of-plane shear modulus, and major and minor Poisson’s ratios. The fiber taper angle has a significant effect on longitudinal and transverse modulus and interfacial stresses. The longitudinal modulus experiences a reduction of 25.9% when increasing the taper angle from [Formula: see text] to [Formula: see text] at a higher fiber volume fraction (40%). However, at a lower volume fraction of the same fiber (10%), the reduction in modulus is limited to 5.74%. Similarly, the transverse modulus is also affected by the taper angle. At the higher fiber volume fraction, there is a decrease of 24.52%, whereas at the lower volume fraction and higher taper angle of the fiber, the decrement is 4.94%.