Advancing mechanical properties of thermoplastic biocomposites through tannic and gallic acids surface treatment of natural fiber reinforcements: A simulation and experimental study

This research explores the mechanical enhancement of thermoplastic biocomposites by altering the surface of natural fiber reinforcements using biodegradable acids, with a particular focus on flax and jute fibers treated with 2% potassium hydroxide (KOH) and various percentages (0%, 1.2%, 1.8% and 2.4%) of bio-based acids (tannic acid and gallic acid). These processed fibers were incorporated into a methyl methacrylate (MMA)-based thermoplastic matrix using hand layup followed by the compression molding to fabricate a composite to achieve 1.97 mm thickness. Surface characterisation using FTIR and TGA demonstrated successful modification of fiber surfaces, improving fiber-matrix bonding. A series of mechanical tests evaluating tensile, flexural, impact, and abrasion behavior demonstrated significant property improvements in the composites. The most consistent and favorable outcomes were achieved with a 1.8% acid treatment, which enhanced critical metrics including tensile strength (60.57 MPa), flexural modulus (5.91 GPa), and impact resistance (8.34 kJ/m 2 ). Finite element analysis (FEA) provided a corroboration for these experimental findings with simulations and the errors obtained when comparing results of maximum stress are approximately 1-3%. Collectively, this evidence positions biodegradable acid treatments as a viable and sustainable method for advancing the performance of natural fiber-reinforced composites toward practical use.