Semnan University Press Progress in Physics of Applied Materials 2783-4794 7 2 2027 07 01 Mechanical Strengthening Enhancement in PMMA/MWCNT/Co₃O₄ Hybrid Nanocomposites: A Comprehensive Study of Compression, Hardness, and Microstructural Properties 17 30 10983 10.22075/ppam.2026.41215.1228 EN Noor H. Majeed College of Science, Department of Physics, Wasit University, Wasit, Iraq 0009-0005-1670-9342 Ali K. Hattab College of Science, Department of Physics, Wasit University, Wasit, Iraq 0000-0002-9869-8659 Ahmad A. Thamer College of Science, Department of Physics, Wasit University, Wasit, Iraq 0000-0003-4243-1100 Reem Hussein Abdullah College of Science, Department of Physics, Wasit University, Wasit, Iraq 0009-0002-1715-1916 Journal Article 2026 05 15 Hybrid nanocomposites of poly(methyl methacrylate) (PMMA) and multi-walled carbon nanotubes (MWCNTs) with cobalt oxide (Co₃O₄) nanoparticles were synthesized and systematically characterized in terms of their mechanical and microstructural properties. The nanocomposites were fabricated by a hand lay-up molding route with equal weight fractions (total loading ranging from 0.5 to 3.0 wt%) of the two nanofillers. Comprehensive characterization was carried out using compression testing (ASTM D695-15), Shore D hardness testing (ASTM D2240), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS/EDX). One-way analysis of variance (ANOVA) was applied to evaluate the statistical significance of the variations in the measured properties. The mechanical properties gradually improved with increasing filler concentration up to 2.0 wt% (1.0 wt% MWCNT + 1.0 wt% Co₃O₄); a further increase in filler concentration led to a deterioration in mechanical properties due to nanoparticle agglomeration. At the optimum composition, the compressive strength increased by 31.3% (from 85.6 ± 2.8 to 112.4 ± 3.2 MPa), the compressive modulus by 29.1% (from 2.85 ± 0.12 to 3.68 ± 0.15 GPa), and the Shore D hardness by 11.3% (from 82.5 ± 1.2 to 91.8 ± 1.0). All of these improvements were statistically significant (p < 0.05). The incorporation of cobalt and the reasonably uniform elemental distribution at lower loadings and increasing heterogeneity at higher filler content has been confirmed by the EDX point analysis and elemental mapping. The improvement is said to be due to the efficient load transfer along the MWCNTs, and to the Co₃O₄ nanoparticles, which are thought to inhibit re-agglomeration of the nanotubes, but since samples with one filler only were not prepared, the inferred synergistic effect is presented as a hypothesis. The results show that PMMA/MWCNT/Co₃O₄ hybrid nanocomposites are an interesting material for structural and protective-coating applications where high mechanical properties are required. https://ppam.semnan.ac.ir/article_10983_76b605730bd2606bbcb290f1244dac9a.pdf