Issue 78

R. Shivashankar et alii, Fracture and Structural Integrity, 78 (2026) 454-473; DOI: 10.3221/IGF-ESIS.78.26

transfer, and increased resistance to debonding and delamination. Previous studies have shown good surface functionalization of basalt fibers with a concentration of 1 wt.% silane without compromising their intrinsic mechanical properties [18] and this concentration was therefore used. Fabrication of hybrid fiber-reinforced epoxy nanocomposites The procedure used to produce Si ₃ N ₄ -filled hemp/basalt fiber-reinforced epoxy (H/B F-Ep) hybrid nanocomposites is shown in Fig. 3. The composite system was composed of an epoxy resin–hardener system as the matrix, plain-weave hemp and basalt textiles as the reinforcing phase, and Si ₃ N ₄ nanoparticles as the nanoscale reinforcement. To achieve the best possible balance between mechanical performance, sustainability, and lightweight qualities, hemp and basalt fibers were hybridized.

Figure 3: Fabrication process of Si 3 N 4 -filled H/B F-Ep nanocomposites. To reduce nanoparticle agglomeration and guarantee uniform dispersion throughout the matrix, Si ₃ N ₄ nanoparticles were mechanically stirred into the epoxy resin prior to composite manufacture, followed by ultrasonication (20–40 kHz) for 30– 60 min. During ultrasonication, intermittent cooling was used to avoid excessive heat accumulation and early epoxy resin curing. The hemp fabrics were treated with 5 wt. % NaOH to improve surface roughness and eliminate surface contaminants, while the basalt fabrics were treated with 1 wt. % silane coupling agent to encourage chemical bonding with the epoxy matrix. Within the multiscale hybrid composite, these surface alterations enhanced fiber–matrix adhesion and facilitated effective stress transfer. The treated hemp and basalt fabrics were piled in the desired hybrid sequence (B/3H/B/3H/B) before the Si 3 N 4 -filled epoxy resin was manually impregnated through the fiber layers using the hand lay-up technique. The laminates were vacuum bagged and subjected to a vacuum pressure of 0.8–0.9 bar for 20–30 min to eliminate trapped air, reduce void formation, and improve resin infiltration. The produced laminates were oven-cured for two hours at 75 °C, post-cured for two hours at 100 °C, and cured for twenty-four hours at room temperature under compression to complete epoxy crosslinking. Waterjet cutting was used to prepare all specimens in order to minimize edge damage and ensure dimensional accuracy. ASTM D2344M, ASTM D790, and ASTM D5045 were followed in the preparation of the specimens for the interlaminar shear, flexural, and fracture toughness tests. Fig. 4 displays representative specimens. Tab. 1 lists the compositions (both wt. % and vol. %) and designations of the hemp/basalt epoxy composites that are untreated, treated, and filled with Si 3 N ₄ .

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