Al2O3/ZnO nanoparticle-embedded bio-hybrid composites: A route to enhanced mechanical strength

The mechanical strengths of human hair, jute, and betel nut husk (BNH) fiber-reinforced polyester composite are enhanced by implanting inorganic nanoparticles. Two bio-hybrid polyester composites—one with ZnO and another with Al₂O₃ nanoparticles—are made up by hand lay-up method with 3–4 mm long 20 % (vol.) fiber loading, 1:1:1 individual fiber ratio, and 5 % (wt.) nanoparticles. Mechanical attributes of composites, such as tensile, flexural, and impact strengths, hardness, and void contents, are evaluated as per ASTM guidelines and compared with an identical composite without nanoparticles. The mechanical strengths of the composite increased remarkably by adding nanoparticles. The composite's tensile, flexural, and impact strengths and hardness are found to be 29.28 MPa, 136.35 MPa, and 0.124 J/mm, and 74.19 (Shore D), respectively, for adding ZnO nanoparticles, and 24.65 MPa, 38.65 MPa, and 0.116 J/mm, and 71.38 (Shore D), respectively, for adding Al₂O₃ nanoparticles. The tensile strength of composites is boosted by 32.78 % and 11.79 %, flexural strength by 278.75 % and 7.92 %, and impact strength by 6.3 and 6.2 times for embedding ZnO and Al₂O₃ nanoparticles, respectively, in contrast to the identical composite without nanoparticles. The hardness and void content are also found favorable for adding nanoparticles. The microcracks, voids, and interfacial bonding between matrix and fibers are investigated through SEM images, revealing that ZnO nanoparticles provide stronger bonding than Al₂O₃ nanoparticles. This study suggests a sustainable approach to enhancing the mechanical strengths of NFRP composites and widens their application. It will promote the implementation of NFRP composites over synthetic fiber-based composites.