Structural, chemical, and multi-scale mechanical characterization of waste windmill palm fiber (Trachycarpus fortunei)

This study investigated the structural, chemical, and multi-scale mechanical properties of windmill palm (Trachycarpus fortunei) leaf sheath fiber, which were frequently wasted. Significant variation was observed in fiber diameter and cross-sectional morphology among different layers in a single leaf sheath, whereas the chemical composition, relative crystallinity index, and the microfibrillar angle (MFA) of palm fibers were almost the same among different layers. Windmill palm fibers had low cellulose contents (34.70-35.5%), low relative crystallinity index (45.7-49.2%), and high MFA (38.8 degrees-29.4 degrees), resulting in low strength and modulus, but high failure strain under tensile load. The tensile fracture surface of windmill palm fibers was assessed through SEM studies and its ductile fracture was confirmed, which can potentially enhance the toughness of composites when used as reinforcement material. Nanoindentation was carried out among different leaf sheath layers, and the results showed the modulus and hardness values of windmill palm fibers are in the same range as other plant fibers. The experimental results may help guide selection of suitable reinforcing fibers for use in composites in different applications.