Effect of Glass Fiber Length on Mechanical and Thermal Behavior of Light Weight Sandwich Composite Made from Expanded Perlite/Glass Fiber/Epoxy Core and Formica as Skin.

Abstract

In this study, we developed a novel, lightweight, and eco-friendly sandwich composite using an expanded perlite core reinforced with glass fiber/epoxy at varying fiber lengths (5 mm, 10 mm, 15 mm, 20 mm, and 25 mm by weight of expanded perlite), and Formica sheets as the outer skins. The objective was to investigate the effect of glass fiber length on the mechanical and thermal properties of the fabricated composites. Specifically, we evaluated flexural and compressive strength, modulus, and toughness, as well as thermal conductivity, to assess the potential of these sandwich structures for sustainable applications.The results show that flexural strength increases from approximately 12 MPa at 5 mm fiber length to a peak of around 16 MPa at 10 mm, followed by a gradual decline and stabilization around 12–13 MPa for fiber lengths between 15 mm and 25 mm. This indicates that a 10 mm fiber length provides optimal flexural strength, while longer fibers offer diminishing returns. Similarly, the flexural modulus rises from about 1500 MPa at 5 mm to a maximum of approximately 1800 MPa at 10 mm. Beyond this, it declines slightly and stabilizes between 1400–1500 MPa for lengths of 15–25 mm, suggesting that 10 mm also yields the best stiffness characteristics.The flexural toughness follows a comparable trend, increasing from 0.18 at 5 mm to a peak of around 0.3 at 10 mm, then gradually decreasing to 0.2 at 15 mm, and further to 0.15 at 20 mm and 25 mm. This demonstrates that 10 mm fiber length provides the highest energy absorption capability, while longer fibers reduce performance, possibly due to fiber agglomeration or poor dispersion. Overall, the findings suggest that a 10 mm glass fiber length is optimal for maximizing the mechanical performance of these sandwich composites, while also maintaining favorable thermal properties for sustainable engineering applications.