Analyzing the influences of fabrication methods on the mechanical properties of Sumberejo kenaf/epoxy sandwich composites with polyurethane foam core

Natural fiber composite sandwich structures have developed significantly to create building materials that are strong and lightweight. The purpose of this study is to compare the cold press and vacuum assisted resin infusion (VARI) methods to investigate the mechanical properties of sandwich composites made of Sumberejo kenaf fiber (KF) reinforced epoxy (EP) as the skin and polyurethane (PU) foam as the core. The kenaf fibers were alkalized by NaOH solution. The results show that manufacturing KF/EP-PU foam sandwich composites using cold press has flatwise tensile strengths that are around (0.220 ± 0.031) MPa higher than VARI, which is only about (0.170 ± 0.057) MPa. This implies that cold press creates an enhanced composite structure. The core shear strength of cold press sample was 17% higher than VARI, with a value of (0.603 ± 0.052) MPa and (0.499 ± 0.016) MPa, respectively. Also, the skin bending stress of cold press sample was (6.106 ± 1.203) MPa while VARI sample had a value of (5.405 ± 0.687) MPa. However, the VARI method exhibited higher flatwise compressive strength with a value (0.393 ± 0.004) MPa and cold press method was (0.331 ± 0.032) MPa. In conclusion, the manufacturing method substantially impacts the mechanical properties of KF/EP-PU foam sandwich composites in this study. This study is a valuable reference for natural fiber sandwich composites as a building material.