Experimental and optimization of interlaminar shear strength and flexural modulus of laminated composite materials under flexural loading

Abstract

Laminated composites have garnered considerable attention in various engineering disciplines due to their impressive strength-to-weight ratios, high stiffness, and exceptional resistance to corrosion, surpassing conventional materials like steel and aluminium. However, when subjected to external loads, laminated composites become susceptible to internal damage, including matrix cracking, delamination, and fibre breakage. These damages can significantly reduce the composites' stiffness and strength. The Interlaminar Shear Strength (ILSS) and Flexural Modulus (FM) are pivotal factors in the flexural failure of composite laminates. This research seeks to explore the ILSS and FM of laminates by investigating variations in laminate thickness, layer sequence, and resin type. Utilizing the hand lay-up technique, laminates of types (0/30/60/90)S, (60/60/30/0)S, and (60/30/60/30)S were fabricated. Analytical assessments of ILSS and FM were conducted based on classical laminate theory. Employing the Taguchi method, an optimization study was executed to identify the key parameters affecting the flexural modulus and interlaminar shear strength of laminated composite materials. The parameters under investigation included layer sequence, resin type, and laminate thickness. Statistical analysis revealed that the layer sequence of the laminate had a more substantial impact compared to the other two parameters. From this investigation, the optimal process parameters for ILSS and FM were determined to be epoxy resin (A), 4 mm thickness (B), and layer sequence of [(30/60/0/90)]s (C). The corresponding values obtained were 34.27 MPa for ILSS and 14.695 GPa for the Flexural Modulus. It was observed that resin (A), thickness (B), and layer sequence (C) contributed to ILSS by 31.92002 %, 0.061646 %, and 68.01833 %, respectively, while for flexural modulus, their contributions were 6.706937 %, 0.084569 %, and 93.20849 %, respectively. To validate the statistical tests against experimental results, a confirmation test was conducted, involving a comparison of the experimental values with the analytical results obtained from the statistical analysis, demonstrating a high level of agreement.