Mechanical Properties of Hand Layup Manufactured Lightweight Sandwich Composites Consisting of Multilayer Carbon Fiber Skin-Reinforced Microballoon Core

Sandwich composites (SC) consist of an outer skin layer surrounded by a porous core. Amphibious aircraft can overcome obstacles in the air and on the water thanks to specially made floaters. They often have retractable landing gear for usage in water and seawater-resistant fuselages. Microballoon (MB) was used to create lightweight material, while carbon fiber was employed in this study to make the SC more rigid and strong. This study aims to characterize the mechanical properties including tensile tests, bending tests, impact Charpy tests, and the density of different SC. The composites were developed using the hand layup method and consisted of an epoxy resin matrix, MB core, and SC2, SC4, or SC6 of carbon fiber skin. The results of mechanical properties of the SC with SC6 demonstrated the best performance on tensile, flexural, and impact compared to SC2 and SC4, especially in longitudinal fiber directions. Tensile strength and modulus, flexural strength, and impact strength as high as 321.0 MPa and 9.3 GPa, 356.6 MPa, and 144.4 kJ/m², respectively, were achieved. The density of SC, i.e., 1.1–1.2 g/cm³, lay between the density of core and epoxy resin. When temperatures are between 200 to 600 °C, epoxy resin deteriorates. Finally, this research reveals the potential of SC with an MB core and multiple layers of carbon fiber skin in applications that require lightweight, high strength, and toughness.