Effect of extension speed on the mechanical performance of sisal and coir fiber bundles

Quasi-static tensile tests are commonly used to determine the mechanical properties of fiber bundles. These tests are generally carried out at a low standard speed of 1 mm.min⁻¹, which is recommended for elementary fibers, although other moderate and high speeds are rarely used. In this study, tensile tests were carried out on coir and sisal fiber bundles from the coastal region of Cameroon using four different speeds: 1, 2, 5, and 10 mm.min⁻¹ to assess mechanical properties. Samples were prepared by attaching the two ends of each randomly selected fiber bundle to a paper frame to obtain a length of 30 mm. The results showed a significant effect of extension speed, indicating a decrease in tensile strength and Young’s modulus, and an increase in strain at break with increasing speed. These trends were correlated with the power functions. A strong dependence between fiber bundle diameter and tensile strength was also observed. Furthermore, statistical analysis based on the Weibull distribution highlighted the dispersion of mechanical properties, demonstrating a reduction in dispersion with increasing extension speed for coir fibers. These data can be used to develop specific standards for these natural fibers and contribute to the advancement of composites based on plant fibers.