This study explores the development of innovative lightweight composites by optimizing stir casting conditions and evaluating the hardness properties of aluminium alloy reinforced with graphene and rice husk ash (RHA). A fixed graphene nanoparticle reinforcement of 0.4 wt.% was used, while the RHA content varied at 0.8 %, 1.2 %, and 1.6 % by weight, with particle sizes of 150 µm, 300 µm, and 600 µm respectively. To guarantee even distribution of reinforcements, the stir casting procedure was carried out at a speed of 140 rpm and a duration of 2 minutes. A statistical method called Response Surface Methodology (RSM) was employed to plan the experiments and enhance the process parameters concerning the hardness of the composite. The resulting cast was machined into a suitable coupon for hardness tests in accordance with ASTM standards. In order to build linear regression equations for the attributes of composites produced under these conditions, the obtained data were subjected to an ANOVA at a 5% level of significance. The influence of RHA weight fraction and particle size on the hardness of the hybrid composite was critically analysed. Results indicated that the incorporation of graphene nanoparticles significantly enhance the hardness of the composite due to their superior mechanical properties and effective load transfer at the matrix-reinforcement interface. Additionally, RHA content and particle size had a substantial impact on the composite’s hardness, with finer particle at optimal weight fraction contributing to better dispersion and interfacial bonding. The developed RSM model showed a strong correlation between experiment and predicted values, validating its effectiveness in optimizing composite fabrication parameters. This study provides valuable insights into sustainable and cost-effective reinforcement of recycled aluminium cans with graphene and rice husk ash for high-performance aluminium-based composites.

Keywords: Aluminum Matrix Composites, Automotive Application, Hardness, Graphene, Particle Size, Response Surface Methodology, Rice Husk Ash, Stir Casting, Weight Fraction, Optimization.

[1] Sujit, K.J. (2014). Optimization of process parameters for optimal MRR during turning steel bar using Taguchi method and ANOVA. International Journal of Mechanical Engineering and Robotics Research, 3(3): 231–24.

[2] Velmurugan, K.V., Dwivedi, Y.D., Kumar, R.A., Madhavarao, S., & Vijayan, V. (2025). Experimental investigation and optimization of stir casting parameters for magnesium hybrid metal matrix composites reinforced with silicon carbide and rice husk ash. AIP Conference Proceedings, 3270: 020202. https://doi.org/10.1063/5. 0211832.

[3] Pandiaraj, V., Ramesh, T., & Muthukumaran, S. (2025). Effect of rice husk ash Si₃N₄ addition on the mechanical, wear, tensile fatigue and creep behaviour of a novel AA7475–TiB₂ metal matrix composite. Discover Materials, 5: 113. https://doi.org/10.1007/s43939-025-00302.

[4] Abdullahi, U., Ohinoyi, G.J., Deyemi, B.K., Anike, K.F., Dan-Asabe, B., Ohotu, S.M., Dambatta, M.S., & Salihi, A. (2025). Investigation and optimization of hardness and tribological behaviour of rice husk ash reinforced aluminium matrix composite using powder metallurgy route. International Journal of Engineering Materials and Manufacture, 10(2): 44–53.

[5] Seshappa, A., Praj, K., Subbaratnam, B., Pranavi, U., Srihithagunapriya, N., & Chhabra, S. (2024). Manufacturing investigations of Al7075/RHA/Al₂O₃ composite by squeeze casting approach. MATEC Web of Conferences, 392: 01027. https://doi.org/10.1051/matecconf/202439201027.

[6] Vishnoi, M., Rai, S., & Verma, N., Maurya, M. (2023). Stir cast AA6351/graphene/TiB₂/rice husk ash composite: Fabrication and assessment of mechanical properties. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 238(10): 4575–4586. https://doi.org/10.1177/09 544062231213182.

[7] Ibrahim, T.K., Yawas, D.S., Dan-Asabe, B., & Adebisi, A.A. (2023). Taguchi optimization and modelling of stir casting process parameters on the percentage elongation of aluminium, pumice and carbonated coal composite. Scientific Reports, 13: 2915. https://doi.org/10.1038/s41598-023-29839-8.

[8] Adesina, O.S., Akinwande, A.A., Balogun, O.A., Adediran, A.A., Sanyaolu, O.O., & Romanovski, V. (2023). Statistical analysis and optimization of the experimental results on performance of green aluminum-7075 hybrid composites. Journal of Composites Science, 7(3): 115. https://doi.org/10.3390/jcs7030115.

[9] Adediran, A.A., Akinwande, A.A., Adesina, O.S., Agbaso, V., Balogun, O.A., & Kumar, B.R. (2023). Modeling and optimization of green-Al 6061 prepared from environmentally sourced materials. Heliyon, 9(8): e18474. https://doi.org/10.1016/j.heliyon.2023.e18474.

[10] Durowoju, M.O., Agunsoye, J.O., Mudashiru, L.O., Yekinni, A.A., Bello, S.K., & Rabiu, T.O. (2017). Optimization of stir casting process parameters to improve the hardness property of Al/RHA matrix composites. European Journal of Engineering Research and Science, 2(11): 5–12. 

[11] Yekinni, A.A., Rabiu, T.O., Adigun, I.A., Sogunro, O.D., & Saheed, R.O. (2018). Tensile properties of recycled aluminium cans reinforced with rice husk ash: Optimization of process parameters. International Journal of Modern Engineering Research, 8(10): 15–22.

[12] Lakhvir, S., Balyyinder, R., & Amandeep, S. (2013). Optimization of process parameters for stir casted aluminium metal matrix composite using Taguchi method. International Journal of Research in Engineering and Technology, 2(8): 375–383.

[13] Sadi, V.M., Widan, M.W., & Suyitno (2015). Optimization of stir casting process parameters to minimize the specific wear of Al/SiC composites by Taguchi method. International Journal of Engineering and Technology, 7(1): 17–26.

[14] Kumar, A.P., Naik, B.J., Rao, C.V., & Rao, S.R. (2013). Optimization of casting parameters for casting of Al/RHA/RM hybrid composite using Taguchi method. International Journal of Engineering Trends and Technology, 4(8): 3284–3288.

[15] Saravanan, S.D., & Kumar, M.S. (2014). Optimization of casting parameters on Al/RHA–Garg composite using Taguchi method. Advanced Materials, 984–985: 291–296.

[16] Yekinni, A.A., Durowoju, M.O., Agunsoye, J.O., & Mudashiru, L.O. (2020). Effect of particle size of rice husk ash on aluminium/graphene composites. IOP Conference Series: Materials Science and Engineering, 805: 012012. https://doi.org/10.1088/1757-899x/805/1/012012.

[17] Yekinni, A.A., Durowoju, M.O., Agunsoye, J.O., & Mudashiru, L.O. (2018). Effects of rice husk ash and graphene on morphological and mechanical properties of recycled aluminium cans hybrid composites. Science Focus: An International Journal of Biological and Physical Sciences, 23(2): 140–155.

[18] Gupta, P., Kumar, D., & Parkash, O. (2016). Structural and mechanical properties of graphene reinforced aluminium matrix composites. Journal of Materials and Environmental Science, 7(5): 1461–1473.

[19] Saravanan, S.D., & Kumar, M.S. (2013). Effect of mechanical properties of rice husk ash reinforced aluminium alloy (AlSi10Mg) metal matrix composites. Procedia Engineering, 64: 1505–1513.

[20] Yekinni, A., Rabiu, T., Adigun, I., Sogunro, D., Saheed, R., & Ademolu, O. (2019). Recycled aluminum cans/rice husk ash: Evaluation of physico-mechanical properties. World Journal of Engineering Research and Technology, 5(1): 18–32.

[21] Dhadsanadhep, C., Luangvaranun, T., Umeda, J., & Kondoh, K. (2008). Fabrication of Al/Al₂O₃ composite by powder metallurgy method from aluminum and rice husk ash. Journal of Metals, Materials and Minerals, 18(2): 99–102.

[22] Luangvaranunt, T., Dhadsanadhep, C., Umeda, J., Nisaratanaporn, E., & Kondoh, K. (2010). Aluminum–4 mass% copper/alumina composites produced from aluminum–copper and rice husk ash silica powders by powder forging. Materials Transactions, 51(4): 756–761.

[23] Prasad, D.S., & Krishna, A.R. (2010). Fabrication and characterization of A356.2–rice husk ash composite using stir casting technique. International Journal of Engineering Science and Technology, 2(12): 7603–7608.

[24] Yolshina, I.A., Muradymov, R.V., Vichuzhanin, D.I., & Smirnova, E.O. (2016). Enhancement of the mechanical properties of aluminum–graphene composites. AIP Conference Proceedings, 1785: 040093. https://doi. org/10.1063/1.4967082.

[25] Bartolucci, S.F., Paras, J., Rafiee, M.A., Rafiee, J., Lee, S., Kapoor, D., & Koratkar, N. (2011). Graphene–aluminum nanocomposites. Materials Science and Engineering A, 528: 7933–7937. 

[26] Sanni, D., Amit, A., & Amar, P. (2020). Material selection for automotive piston component using entropy–VIKOR method. Silicon, 12: 155–169. https://doi.org/10.1007/s12633-019-00129-6.

[27] European Aluminium Association (2011). The aluminium automotive manual. http://www.european-alumi nium.eu.

Source of Funding:

This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Competing Interests Statement:

The authors declare that they have no competing interests related to this work.

Consent for publication:

The authors declare that they consented to the publication of this study.

Authors' contributions:

All the authors made an equal contribution in the Conception and design of the work, Data collection, Drafting the article, and Critical revision of the article. All the authors have read and approved the final copy of the manuscript.

Institutional Review Board Statement:

Not applicable for this study.