Hybrid carbon and glass fiber-reinforced composites have attracted significant research interest for primary load-bearing structural components in the field of aviation manufacturing owing to their low weight and high strength to weight ratio. However, the anisotropic and heterogenic nature of carbon and/or glass fiber-reinforced composite prevents high machining quality due to the directionality effect of fibers in the polymer matrix. As such, this study investigates the effect of drilling process for hybrid fiber-reinforced composite and reports optimal drilling parameters to improve the drill quality. Experimental studies indicate that an increased point angle (i.e., from 80° to 120°) resulted in low delamination upon entry due to reduced thrust force, which in turn produces better surface finish with minimal tool wear. The optimal feed rate (0.2 mm/min) ensures lower delamination at entry, since higher feed rates can increase the thrust force due to elevation in the shear area or raise the self-generated feed angle, which in turn reduces the effective clearance angle. To this end, drilling parameters were optimized using Dandelion optimizer (DO)—a cutting-edge metaheuristic search algorithm (MSA). We report the excellent consistency of DO to solve the proposed drilling optimization problem while achieving promising results as ascertained by the small standard deviation values.

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The research objective of this work is to reuse graphite rods recovered from used batteries and utilize them as an additive in SAE20W40 oil to improve the engine parts’ lubrication ability and wear resistance. The graphite rods are grated to obtain ultra-fine particles and then chemically exfoliated using an Improved Hummer's process that results in graphene oxide. Then, it is thermally reduced at 350 °C to yield reduced graphene oxide. Different ratios (0.25, 0.50, 0.75, and 1.00 wt.%) of as-grated graphite particles and reduced graphene oxide were dispersed in the above oil to form a colloidal solution and then used for tribological studies. The graphite particles and synthesized reduced graphene oxide were characterized using X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. X-ray diffraction data confirms the presence of graphite, graphene oxide, and reduced graphene oxide in the prepared powders and matches with the standard files. High-resolution transmission electron microscopy images reveal the presence of multilayer sheets with an interplanar distance of 0.34 nm having wrinkles, folds, and gas holes. The G and D band positions of Raman spectra prove the formation of oxygenated functional groups, and the ID/ IG ratio confirms the defects in graphene oxide and reduced graphene oxide. The viscosity of prepared lubricant increases by 35% and 21% for graphite and reduced graphene oxide, respectively. The results of tribological studies with 0.25 wt.% graphite and 0.5 wt.% reduced graphene oxide lubricants showed improvement in coefficient of friction by 32% and 36%, respectively. At these optimal concentrations, the specific wear rate dropped by 51% for reduced graphene oxide. Scanning electron microscopy/energy dispersive spectroscopy, images show that the nanolubricant's mending effect over the worn surface improves reduced graphene oxide added SAE20W40 oil tribological characteristics. From the results, reduced graphene oxide synthesized from as-grated graphite rods proves to be a low-cost, sustainable, and effective friction modifier for engine oils.

The present study intends to evaluate the tribological characteristics of Copper (Cu) and Copper oxide (CuO) based nanolubricant for its use in machine tool slideways. Different sizes of copper and copper oxide particles were chosen and physical characterisation were carried out using scanning electron microscope (SEM) and transmission electron microscope (TEM). The nanolubricants were prepared by adding various proportions (0.1%, 0.25%, 0.4% wt) of the particles in Polyalphaolefin (PAO) base oil with lecithin and oleic acid surfactants. Friction and stick-slip characteristics of the nanolubricants were assessed using pin-on-block reciprocating friction monitor simulating the actual loading conditions prevailing in machine tool slideways. Studies were also conducted under elevated temperatures to ascertain the performance of particles at higher temperatures. Extreme pressure properties of the lubricants were studied using Four Ball Tester. The results of the experiments were compared with ISO VG 32 oil, a conventional mineral lubricant meant for machine tool slideways and it was found that the tribological properties nanolubricants using both the nanoparticles were considerably better. The coefficient of friction found to be decreased by 2.5% and 17.5% for copper particles with 0.1% weight composition in ambient temperature and elevated temperature respectively. Whereas for copper oxide particles with 0.1% weight composition a reduction of 14.25% and 10% were obtained.