Silane-Grafted Bamboo Fiber and SiC Dispersion-Strengthened Epoxy Composites: Mechanical Performance and Hygrothermal Durability

Abstract

Recently, Biocomposites are gaining rapid industrial application due to their unlimited structural integrity and environmental sustainability. In this study, the mechanical and hygrothermal performance of epoxy matrix biocomposites reinforced with chemically modified bamboo fibers and dispersion-strengthened with silicon carbide (SiC) particulate fillers is investigated. Bamboo fibers were subjected to sequential surface treatments comprising alkaline mercerization with 0.1 N NaOH and silane coupling using the Gelest hydrolysis method, yielding four composite typologies: untreated bamboo–epoxy (UBE), NaOH-treated bamboo–epoxy (NBE), NaOH–silane-treated bamboo epoxy (NSBE), and SiC-filled NaOH–silane-treated bamboo–epoxy (NSBES). Composite laminates were fabricated by hand lay-up with compression consolidation and post-cured at 80°C. Tensile, flexural, and moisture absorption tests were conducted in accordance with ASTM D3039, ASTM D790, and ASTM D570 standards, respectively. Under dry conditions, alkali treatment (NBE) raised peak tensile strength by 23.97% over untreated composites at an optimal 15 vol% fiber loading, while combined NaOH–silane treatment (NSBE) further improved it by 39.96% to 64.8 MPa. The addition of 10 vol% SiC to the NSBE system (NSBES) yielded a peak tensile strength of 89.6 MPa, representing a 38.27% gain attributable to dispersion-strengthening mechanisms that impede matrix crack propagation. Flexural strength similarly peaked in the NSBES system, with SiC raising it by 67.32% at 10 vol% bamboo fiber loading compared to unreinforced composites. Under moisture-saturated conditions, NSBES retained the best hygrothermal stability, recording a wet tensile strength of 74.3 MPa surpassing even the dry UBE baseline of 46.3 MPa and the lowest saturation moisture content (W% = 0.92%). Moisture absorption kinetics followed a dual Fickian/non-Fickian diffusion regime, with the diffusion coefficient decreasing systematically across the treatment hierarchy. These results demonstrate that the synergistic combination of silane grafting and SiC dispersion strengthening yields high-performance, moisture-resistant natural fiber composites well-suited to structural, automotive, marine, and construction applications where both mechanical integrity and environmental durability are required.