OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Fig. 6. Untreated fibers (500×) Fig. 7. Treated fibers Fig. 8. Untreated fibers (1,000×) Fig. 9. Treated fibers Fractured tensile specimens were selected to study the failure mechanisms and interactions between the matrix and fibers in the composites. SEM analysis was performed at ×500 and ×1,000 magnification, with four specimens being examined in detail at these two magnification levels. Figures 6–9 show a comparison of the SEM images of the tensile-tested composites with and without Sida cordifolia fibers, both untreated and treated. At ×1,000 magnification, it was observed that the hemicellulose layer was preserved on the surface of the untreated Sida cordifolia fibers, which was absent on the fibers subjected to benzoylation treatment. The removal of the hemicellulose layer increases the wettability of the fibers, contributing to the increase in the tensile strength of the benzoylation-treated composites. Notably, the fiber elongation was more pronounced in specimens 3 and 4 containing Sida cordifolia fibers treated with benzoylation compared to the untreated variants. This observation highlights the increased tensile strength of the composites with the treated fibers, which is attributed to the stronger fiber-matrix bonding. The increased fiber elongation reflects its increased load-bearing capacity due to its higher wettability after treatment. Conclusion A study involving the use of four different compositions of a 7-layer polymer composite demonstrated significant improvements in mechanical properties while maintaining a constant amount of fiber material. Tensile, flexural tests and scanning electron microscopy (SEM) investigation showed optimum values reflecting the effectiveness of the developed composite.
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