Issue 78

R. Shivashankar et alii, Fracture and Structural Integrity, 78 (2026) 454-473; DOI: 10.3221/IGF-ESIS.78.26 • The mechanical response determined the ideal Si 3 N ₄ concentration. Fracture toughness was best in S2 (1 wt. %), while flexural strength, flexural modulus, and ILSS were highest in S3 (1.5 wt. %). These patterns could be connected to variations in interfacial reinforcement and nanoparticle dispersion. • Fiber pull-out, interfacial debonding, matrix cracking, and fiber fracture were among the failure characteristics of untreated and treated/nanoparticle-filled composites that differed according to SEM fractography. These findings align with the mechanical and fractured responses that have been assessed. • Nanoparticle agglomeration, higher void content, and localized stress concentrations, which might lower the effectiveness of stress transmission and crack-arrest processes, may be linked to the minor decrease in mechanical performance at 2 wt. % Si ₃ N ₄ . Overall, the ILSS, flexural characteristics, fracture toughness, and SEM results validate the cooperative involvement of optimally dispersed Si 3 N ₄ nanoparticles and surface-treated hemp/basalt fibers in creating structurally sound and damage tolerant epoxy composites. The optimized nanocomposites exhibit promise for advanced engineering, aeronautical, and lightweight automobile applications. Future work should focus on evaluating the long-term durability of the optimized hybrid nanocomposites, including their moisture absorption, thermal stability (TGA and DMA), fatigue behaviour, and resistance to environmental ageing, in order to establish their reliability and performance under service conditions. [1] Faruk, O., Bledzki, A. K., Fink, H. P., Sain, M. (2012). Biocomposites reinforced with natural fibers: 2000–2010, Progress in Polymer Science, 37(11), pp. 1552–1596. DOI: https://doi.org/10.1016/j.progpolymsci.2012.04.003. [2] Dittenber, D. B., Ganga Rao, H. V. S. (2012). Critical review of recent publications on use of natural composites in infrastructure, Composites Part A, 43(8), pp. 1419–1429. DOI: https://doi.org/10.1016/j.compositesa.2011.11.019. [3] Alao, P. F., Press, R., Kallakas, H., Ruponen, J., Poltimäe, T., Kers, J. (2022). Investigation of efficient alkali treatment and the effect of flame retardant on the mechanical and fire performance of frost-retted hemp fiber reinforced PLA, Polymers, 14(11), 2280. DOI: https://doi.org/10.3390/polym14112280. [4] Thomas, L., Ali, M., AjuKumar, V. N., Zainuddin, S., Jeelani, S. (2023). Investigations of thermo-mechanical properties of cryogenic and dual alkali-anhydrous treated hemp fiber and its composites Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications, 237(23). DOI: https://doi.org/10.1177/09544062231164544. [5] Jawaid, M., Abdul Khalil, H. P. S. (2011). 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