Performance evaluation of foxtail millet husk biosilica-dispersed epoxy composites reinforced with hybrid fibers: green material for sustainable development
摘要
The growing demand for sustainable and high-performance composite materials has driven the development of hybrid biobased reinforcement systems. In this context, hybrid fiber composites were fabricated using (10 vol% hemp fiber and 30 vol% lyocell fiber) along with foxtail millet husk-derived biosilica treated with silane coupling agents. The crystallinity characteristics of the extracted biosilica were analyzed using X-ray diffraction (XRD). The composites were evaluated according to ASTM standards for mechanical properties including tensile, flexural, impact strength, and hardness, along with interlaminar shear strength (ILSS), thermal conductivity, and water absorption behavior. The incorporation of silane-treated biosilica significantly enhanced the mechanical and shear properties due to improved interfacial bonding and dispersion. Among the fabricated composites, ES3 (3 vol% biosilica) exhibited the best overall performance, achieving a tensile strength of 61.9 MPa, flexural strength of 104.8 MPa, impact energy of 4.9 J, Shore D hardness of 79.6, and ILSS of 38.79 MPa. Scanning electron microscopy (SEM) revealed improved interfacial adhesion and reduced fiber pullout, confirming the effectiveness of silane treatment. In contrast, the composite with the highest filler loading (ES5) demonstrated the maximum thermal conductivity (0.61 W m–1 K–1) and water absorption (2.20%), which is attributed to enhanced heat conduction pathways and increased porosity at higher biosilica content.