Tensile Strength Characterization of Alkaline-Treated and Untreated Banana Fibres Using Weibull Statistics

Banana fibres (BFs), derived from the pseudo-stems of Musa acuminata, represent a widely available agricultural residue with strong potential as an eco-friendly reinforcement in composite materials-particularly in bio-based epoxy or thermoplastic systems used in automotive interiors, packaging, and lightweight construction. However, their inherent variability presents challenges for consistent and reliable mechanical characterisation. This study investigates the effect of wood ash treatment, an eco-friendly alternative to conventional alkaline processing, on the tensile strength of single BFs. Fibres were treated in aqueous wood ash solutions at two pH levels (12.4 and 13.5) and soaking durations of 3 h and 24 h, and then tested according to ASTM C1557. At least 50 valid tensile tests per series were performed, and the results were analysed using a two-parameter Weibull distribution to quantify characteristic strength and variability, complemented by reliability analysis to assess survival probability. Untreated fibres exhibited low characteristic strength (396.6 MPa) and a Weibull modulus of 1.79, confirming significant scatter. Treated fibres showed marked improvements: the highest characteristic strength was achieved at pH 13.5 for 3 h (552.8 MPa, m = 3.17), while the greatest uniformity was observed at pH 13.5 for 24 h (m = 4.62). Reliability curves confirmed superior performance of treated fibres, with 75% survival strengths up to 373 MPa compared to 198 MPa for untreated. These findings demonstrate that wood ash treatment enhances both the strength and reliability of BFs for sustainable composite applications.