<![CDATA[Natural fiber-reinforced hybrid composites have attracted considerable attention as environmentally friendly materials owing to their low density, renewability, and promising mechanical properties. However, studies investigating the combined effect of coconut coir fiber and ramie fiber volume fractions on the tensile strength, impact resistance, and fracture characteristics of epoxy-based hybrid composites remain limited. This study aims to evaluate the influence of different volume fraction combinations of coconut coir fiber and ramie fiber on the mechanical performance and fracture behavior of hybrid composites. Composite specimens were fabricated using the hand lay-up method with an epoxy matrix. Tensile and impact tests were conducted according to ASTM D3039 and ASTM D6110, respectively, followed by macro-fracture observation and scanning electron microscopy (SEM) analysis to identify dominant failure mechanisms. The results indicate that the hybrid composite containing 15% coconut coir fiber and 15% ramie fiber exhibited the highest tensile strength of 19.58 MPa and the highest impact strength of 16.9 kJ/m². This balanced fiber composition promoted more uniform stress distribution, improved fiber–matrix interfacial bonding, and reduced the occurrence of voids and fiber pull-out compared with other compositions. Fractographic analysis confirmed that enhanced interfacial adhesion contributed to improved mechanical performance. These findings demonstrate that optimizing the volume fraction of hybrid natural fibers is an effective approach for improving the tensile, impact, and fracture properties of epoxy-based hybrid composites]]>
