Mechanical behavior of sisal glass-reinforced polymer composites under tensile loading and geometric irregularities

The study aims to evaluate the tensile behavior of sisal glass-reinforced polymer composites with varying geometric irregularities. Composite laminates were fabricated using a hand layup technique, incorporating sisal fiber woven reinforcement and ortho-phthalic unsaturated polyester resin. The laminates, configured with 7 and 9 layers, were subjected to tensile testing with and without 6 mm and 12 mm diameter central holes and double holes spaced at 6.2 mm, 12 mm, and 48 mm intervals. The tensile tests were conducted using an electromechanical test system, and the results were analyzed to determine the ultimate tensile strength, modulus of elasticity, and failure strain for each specimen type. The findings revealed significant differences in tensile strength depending on the presence and size of the holes. Specimens with central holes exhibited a reduction in tensile strength, with the extent of strength reduction dependent on the hole diameter. Larger holes resulted in more severe stress concentrations, leading to greater strength degradation. Double-hole specimens showed similar strength reduction patterns, with closer spacing exacerbating the stress concentration effects. The residual strength ratio (RSR) for different configurations conformed to expected values for fiber-reinforced composites with circular hole-type defects. The study underscores the critical impact of geometric irregularities on the mechanical performance of sisal glass-reinforced polymer composites. These findings can guide the development of design strategies to mitigate the adverse effects of stress concentrators, thereby enhancing the reliability and durability of these materials in practical applications.