Samant Gaurish Mahabaleshwar
Mechanical Engineering Department, Goa College of Engineering, Goa University, Farmagudi, 403401, Ponda, Goa, India.

Rajesh S. Prabhu Gaonkar
Mechanical Engineering Department, Goa College of Engineering, Goa University, Farmagudi, 403401, Ponda, Goa, India.

DOI https://doi.org/10.33889/PMSL.2026.5.2.019

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Abstract

This study uses scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to develop an in depth understanding of the structural property of cashew nutshell liquid (CNSL) based composites reinforced with local natural fibres like Stocksii bamboo, areca nut leaf and coconut mid rib. Quantifiable SEM data were combined with elemental profiling across key microstructural regions to assess the effectiveness of chemical treatments, fibre matrix interfacial bonding, failure mechanisms, nano filler, and microstructural changes during manufacturing. Alkaline treatment reduced fibre diameter and increased surface roughness, consistent with the selective removal of hemicellulose and waxy layers as confirmed by EDS. Silane treatment produced polymerised interphase, reflected in an 18.6% reduction in silicon and a 79% rise in sulphur content, establishing complementary chemical and mechanical bonding mechanisms. It was observed that Interfacial quality has significantly improved, with contact length increasing from 67.3% in untreated natural fibres to 93.1% in the treated fibres, supported by maximum interfacial oxygen and sulphur accumulation. A significant change from brittle pullout failure in untreated composites to fracture dominated behaviour in treated systems was observed by fractography analysis, which clearly correlated with improved interfacial bonding. Incorporating nano filler which resulted in a distinctive triple phase fibre matrix nanofiller interface with higher oxygen of 44.27 wt%, silicon with 9.42 wt%, and calcium concentration of 6.5X, which resulted into improved fracture toughness. Manufacturing method comparison exhibited that compression moulding produced the most refined microstructure comparative to vacuum bagging and hand layup. It was observed that significant linear association between tensile strength and interfacial contact length, showing that mechanical parameters can be effectively estimated from microstructural observations. Overall, the SEM EDS analysis shows that CNSL based natural fibre composites could achieve interfacial bonding and microstructural integrity similar to synthetic polymers. These results show that CNSL based green composites are both economically and technologically viable as high performing, sustainable materials obtained from renewable resources.

Keywords- Cashew nutshell liquid, Alkali and silane treatment, Natural fibre, SEM and EDS analysis.

Citation

Mahabaleshwar, S. G., & Gaonkar, R. S. P. (2026). Microstructural Characterization of CNSL Based Natural Fibre Composites Using SEM and EDS Techniques. Prabha Materials Science Letters, (2), 338-361. https://doi.org/10.33889/PMSL.2026.5.2.019.