Alkali Treatment Effects on the Tensile Characteristics of Vacuum-Infused Banana and Flax Woven Fiber Composites

This experimental research work investigates the alkali treatment of natural fiber-reinforced composites (NFRCs) prepared from banana and flax woven fibers for mechanical behavior. The fundamental purpose of this study is to explore the Banana and Flax woven fibers as reinforcement in polymer composites, regarding different concentrations of alkali solution (4%, 6%, and 8%) and their influence on the tensile properties of the two natural fibers. The density of each developed composite is also evaluated. The composites were made using a vacuum infusion process, providing good impregnation and uniform resin distribution. A tensile test was conducted using ASTM D3039 for tensile strength, modulus, and tensile strain behavior. For untreated samples of banana fiber composites, ductility was comparatively high at 34% strain, with a moderate tensile strength of 26.12 MPa. Application of a 6% alkali treatment elevated tensile strength to 42.83 MPa and tensile modulus to 772.82 MPa, albeit at a reduced ductility of 5.4%. These results suggest enhanced interfacial bonding but greater brittleness. Flax fiber composites had a different response, where untreated flax fiber-reinforced composites exhibited a tensile strength of 49.55 MPa, a tensile modulus of 391.33 MPa, and a ductility of 8.48%. In contrast, alkali treatment markedly enhanced ductility, peaking at 16.02% for the 4% treated composites. Each composite, regardless of being untreated or alkali-treated, exhibited distinct mechanical behavior when processed under varying concentrations, illustrating the optimization depth needed for each fiber type to achieve the desired strength, stiffness, and ductility. The study does illustrate the potential of tailored alkali treatments in the form of enhanced performance on composite materials made with banana and flax woven fibers, reinforcing the materials’ prospects for sustainable lightweight structural solutions.