Hole size influence on the open hole tensile and flexural characteristics of aramid-basalt/epoxy composites

The open hole tensile and flexural test of composites holds immense importance in aerospace and structural engineering. These tests provide critical insights into how composites perform under real-world conditions, allowing for the development of materials that meet rigorous standards, thereby ensuring the safety and durability of aircraft and other applications. This study investigates the influence of hole size on the open hole tensile (OHT) and flexural properties (OHF) of plain weave aramid/epoxy (AFRP), basalt/epoxy (BFRP), and aramid-basalt/epoxy (ABFRP) inter-ply hybrid laminates. Laminates were fabricated using hand layup followed by the compression molding method. The specimens were cut according to ASTM D5766 and ASTM D7264 to analyze OHT and OHF performance for three different hole sizes viz., 4, 6, and 8 mm. Results indicated that the ABFRP inter-ply layup composite significantly enhanced the mechanical performance of when compared to AFRP laminates. However, the decline in mechanical properties was observed in all the composites with the increase in hole size. BFRP laminates showed higher hole sensitivity under tensile loading due to its brittle fracture mechanism while AFRP exhibited higher hole sensitivity under flexural loading which can be attributed to its the poor compressive strength. The effect of hole size on the damage mechanism has also been highlighted through scanning electron microscope (SEM). The fibre fracture was observed to be dominant failure mechanism in large hole specimens while matrix cracking and delamination were found to be dominant failure mechanism in small holes.