In recent years, the development and use of composite materials are gaining importance in the field of aerospace, automobile, marine and other industrial applications because of their potential properties such as higher specific strength and better corrosion and fatigue properties than most metals. The ever-increasing temperatures on earth surface and the use of non-biodegradable materials for industrial applications lead to increase in global warming which forced the researchers to work on green composites that suite the properties and reliability of the metals, alloys, composites. The increase in use of polymers which are not biodegradable increases air and water pollution. Development of green composites helps to maintain ecological balance. The review of this article focuses on discussing the green matrix material and modifications needed for fibers to improve the properties of green composites.

WC–Co composite material is highly demanded in manufacturing industries, because of its unique properties such as excellent hardness with toughness, higher mechanical strength, and good dimensional stability. The present investigation is aimed at studying the impact of different experimental conditions (by varying cobalt content, thickness of work piece, tool profile, tool material, abrasive grit size, and power rating) on responses of interest (material removal rate and tool wear rate) in ultrasonic drilling of WC–Co composite material. The experiments have been planned by using Taguchi's L-36 orthogonal array and grey relation analysis has been applied for optimization of multiple responses. Analysis of variance is also employed to find the significant factors. Significant effects are observed for process variables such as cobalt content, abrasive grain size, and power level. Tools with higher hardness delivered better machining performance.

This study has focused on the evaluation of the influence of different input variables (cobalt content, thickness of workpiece, tool profile, tool material, size of abrasive grains, and power rating) on the hole quality (dimensional and form accuracy) obtained in ultrasonic machining of WC-Co composite material. Taguchi's approach has been employed for planning the experiments and optimization of the experimental results. Three measures of hole quality (hole oversize, out of roundness, and conicity) have been investigated under controlled experimental conditions. The experimental results showed that abrasive grit size and power rating were most influential for the hole quality. Hole quality has been found to be improved at higher cobalt content, whereas it is found to be degraded with the use of coarse grit size.

This article addresses the application of grey based fuzzy logic coupled with Taguchi's approach for optimization of multi performance characteristics in ultrasonic machining of WC-Co composite material. The Taguchi's L-36 array has been employed to conduct the experimentation and also to observe the influence of different process variables (power rating, cobalt content, tool geometry, thickness of work piece, tool material, abrasive grit size) on machining characteristics. Grey relational fuzzy grade has been computed by converting the multiple responses, i.e., material removal rate and tool wear rate obtained from Taguchi's approach into a single performance characteristic using grey based fuzzy logic. In addition, analysis of variance (ANOVA) has also been attempted in a view to identify the significant parameters. Results revealed grit size and power rating as leading parameters for optimization of multi performance characteristics. From the microstructure analysis, the mode of material deformation has been observed and the critical parameters (i.e., work material properties, grit size, and power rating) for the deformation mode have been established.