Exploring the high elongation at break of windmill palm fiber

The windmill palm tree, renowned for its exceptional wind resistance, boasts the highest tensile elongation among plant fibers. Despite this, the origin of its remarkable tensile properties remains uncertain due to the intricate microstructure of the fibers and the short length (less than 1 mm) for each single fiber. This study focuses on windmill palm materials, investigating their fiber bundles and single fibers to examine microstructure, chemical composition, mechanical properties, and thermal characteristics. Findings reveal that windmill palm fiber possess a multicellular structure, with spindle-shaped single fiber parallelly aligned to create the overall fiber. By eliminating lignin and hemicellulose, highly crystalline (76.5 %) single fibers can be isolated. By loading resin microspheres at both ends of the fibers, the mechanical properties of single fibers can be successfully tested. The windmill palm single fibers exhibited a tensile strength in the range of 263±127 MPa, demonstrating a robust resistance to breaking under tension. Additionally, these fibers showcased a tensile elongation of 25.1±10.2 %, indicating a notable capacity for deformation before failure. The large strain fracture of windmill palm fibers mainly originates from the high tensile elongation of single fibers for the low molecular chain orientation, followed by the stretching of the amorphous regions such as lignin and hemicellulose at the connections between single fibers.