Enhancing Mechanical and Impact Properties of Flax/Glass and Jute/Glass Hybrid Composites Through KOH Alkaline Treatment

This research investigates the influence of potassium hydroxide (KOH) treatment on the mechanical, flexural, and impact properties of flax/glass and jute/glass hybrid composites. Hybrid composite materials have been developed, incorporating natural fibers that are both treated and untreated by KOH, with glass fiber within an epoxy matrix. Natural fibers, such as flax and jute, were chemically treated using different KOH concentrations and immersion times specific to each fiber type. Following the treatment, both fibers were rinsed with distilled water and subsequently dried. The natural fiber's chemical interaction was analysed using FTIR. Hybrid composites were fabricated via the integration of intercalated layers of natural fibers and glass fiber using hand layup followed by compression molding. Mechanical properties, including impact resistance, flexural strength, elastic modulus, and tensile strength, were evaluated in accordance with ASTM guidelines. KOH-treated flax/glass composites (T-F2G2) demonstrated enhanced fiber-matrix bonding, indicated by elevated tensile strength (118.16 MPa) and flexural strength (168.94 MPa) relative to untreated samples. The impact strength of T-F2G2 composites increased to 39.33 KJ/m² due to the removal of impurities and exposure of hydroxyl groups, which interact with K⁺ ions in KOH, thereby improving their mechanical properties. SEM analysis of cracked surfaces confirmed enhanced bonding and reduced fiber pull-out, indicating improved interfacial compatibility. The findings demonstrate that KOH treatment effectively preserves cellulose integrity and enhances fiber-matrix interactions, positioning it as a viable alternative to NaOH for hybrid composites suitable for lightweight and environmentally sustainable industrial applications.