Impact of fiber diameter on mechanical and water absorption properties of short bamboo fiber-reinforced polyester composites

This study aims to investigate the effect of fiber diameter on the mechanical and water absorption characteristics of short bamboo fiber-reinforced polyester composites. Three different fiber sizes (180–250 µm, 250–500 µm, and 700–1000 µm) were used to prepare composites with varying fiber loadings of 10 wt.%, 20 wt.%, and 30 wt.%. The fabricated composites were cut to standard dimensions, and tension tests, impact tests, and water absorption tests were performed. Reproducible results were obtained, revealing that using fibers of smaller diameter (180–250 µm) increased the tensile strength of the composite by 20 % compared to composites with larger diameter fibers (700–1000 µm), while the tensile modulus showed a 22 % enhancement with decreasing fiber diameter. Composites with larger diameter fibers exhibited more defects (voids and matrix detachment), as revealed by SEM analysis of fractured surfaces. The impact strength of composites with a diameter size of 700–1000 µm increased by 33 % compared to composites reinforced with the smallest fiber diameter. Water absorption of the composites was also studied by long-term immersion in water, showing that water intake was high initially, reaching a saturation point after a certain time interval. The absorbed water values indicated that composites with the smallest diameter (180–250 µm) showed maximum water intake due to the creation of more water intake sites (increased interfacial area), while composites with the largest diameter fibers (700–1000 µm) exhibited the least water absorption as the interaction region between fibers and matrix was reduced.