Natural fiber composites have attracted global attention due to their lightweight, low-carbon footprint characteristics as well as good mechanical properties. Due to these distinct advantages, the application spectrum of these composites has grown at an unprecedented rate. These composites are used for making a wide variety of sophisticated engineering products; therefore, certain degree of machining operations is necessary for assembly purposes. Drilling is an indispensable machining operation that is frequently performed for making of holes to facilitate assembly of several components into an intricate part. In the present research endeavor, the drilling behavior of unidirectional sisal-epoxy and sisal-polypropylene composite laminates has been experimentally investigated. Chip formation characteristics in the context of both thermoset and thermoplastic natural fiber composite laminates have been discussed. Further, the analysis of drilling force signals has been reported and the mapping of drilling forces has been proposed. Influence of drill geometry, feed, and spindle speed on drilling forces and a comparative analysis of damage characteristics of drilled hole have also been reported. From the current research work, it has been established that the tooling requirement for drilling of composite laminates under investigation is substantially different.

Natural fiber-reinforced composite materials are finding wide acceptability in various engineering applications. A substantial increase in the volume of production of these composites necessitates high-quality cost-effective manufacturing. Drilling of holes is an important machining operation required to ascertain the assembly operations of intricate composite products. In the present experimental investigation, natural fiber (sisal and Grewia optiva fiber)-reinforced polylactic acid-based green composite laminates were developed using hot compression through film stacking method. The drilling behavior of green composite laminates was evaluated in terms of drilling forces (thrust force and torque) and drilling-induced damage. The cutting speed, feed rate, and the drill geometry were taken as the input process parameters. It was concluded that all the three input process parameters affect the drilling behavior of green composite laminates. The drill geometry was established as an important input parameter that affects the drilling forces and subsequently the drilling-induced damage.

The use of polymer–matrix composites in structural applications necessitates certain degree of machining operations to meet the final product integrity. Drilling is an essential machining operation being used in composite industries for making of holes for bolted joints. The conventional drilling, which is frequently used for making holes in polymer–matrix composite parts, is not convenient anymore because of plethora of challenges encountered. The major drawback is the drilling-induced damage, which mainly occurs due to the direct interaction between the tool and composite laminate. Therefore, there exists a research opportunity to develop cost-effective high-quality machining methods for composite laminates. In the present research endeavor, rotary-mode ultrasonic drilling process has been conceptualized and developed for the drilling of fiber-reinforced polymer composites. The influence of various process parameters including power rating, slurry concentration, and abrasive size on material-removal rate, tool wear rate, and average surface roughness (R_a) has been experimentally investigated. It has been observed that the entry and exit delamination is prevented, and hole circumferential edge quality is improved when holes are produced through rotary-mode ultrasonic drilling as compared to the conventional drilling. It has also been found that with substantial modification in the conventional ultrasonic drilling process, the drilling performance in terms of material-removal rate of glass-epoxy laminates can be significantly improved. The major contribution of the present research endeavor is the development of a novel method of making clean-cut damage-free holes in fiber-reinforced composite laminates.

In the midst of a huge demand for high-precision miniaturized medical implants made up of potential biomaterials, the biomedical Ti-6Al-4V alloy meets the uncompromising standards for longevity, biocompatibility, and sterilizability required to interact with living cells in medical settings. This research tailored the existing capabilities of a traditional micro-electric discharge machining (µ-EDM) setup by adding 0, 2, 4, 6, 8, and 10 g/l bioactive zinc powder particle concentrations (PPCs) to the dielectric. A copper and brass micro-tool electrode (C-µ-TE and B-µ-TE) was employed in association with each PPC. Experiments were executed using the one-variable-at-a-time (OVAT) approach. Machining time and dimensional deviation were chosen as the response variables of Zn powder mixed-micro-EDM (Zn-PM-µ-EDM). According to the analytical findings, the combination of C-µ-TE and 6 g/l Zn PPC achieved 23.52%, 3.29%, and 17.96% lesser machining time, dimensional deviation, and recast layer thickness, respectively, compared to the B-µ-TE. The detailed study of this surface endorsed a significant modification in terms of improved recast layer thickness (26.44 µm), topography (Ra = 743.65 nm), and wettability (contact angle < 90 deg), suggesting its dental application. In addition, the observation of ZnO and TiO in X-ray diffraction and appealing in vitro cytocompatibility encourage the subsequent biological and therapeutic studies to validate the anticipated antiviral activity of the modified Ti-6Al-4V alloy surface against coronavirus (COVID-19).