Toughness Evaluation of Sedge Fiber-Reinforced Epoxy Composites Under Dynamic and Quasi-Static Loadings

Composite materials, particularly those with fiber-reinforced polymer matrices, align well with current demands for combining low density with high mechanical strength. This has motivated extensive research into natural lignocellulosic fiber-reinforced polymeric matrices. In this context, the present study evaluates the toughness of untreated and alkali-treated 30 vol.% sedge fiber (Cyperus malaccensis)-reinforced epoxy matrix composites. This study provides a comprehensive assessment of dynamic and quasi-static mechanical properties. The dynamic toughness performance was evaluated through Izod and Charpy impact, whereas quasi-static toughness was evaluated using tensile, flexural, and compressive tests. To allow for a proper comparison, toughness units were all considered in joules (J) by taking into account the specimen dimensions. The fracture surfaces were examined to evaluate the influence of fiber treatment on failure mechanisms. Scanning electron micrographs depicted a substantial reduction in interfacial delamination of composites reinforced with treated fibers, suggesting improved fiber–matrix adhesion. The results revealed a significant difference attributable to the alkali treatment. Specifically, the treated-fiber composite group showed the highest impact energies, achieving values of 7.84 J for Izod and 15.5 J for Charpy. The alkali-treated fiber composites exhibited quasi-static energy absorption values of 2.78 J, 4.32 J, and 11.06 J under tensile, flexural, and compressive loading, respectively.