MACHINING OF FIBER-REINFORCED COMPOSITES

Abstract

Since the introduction of glass fiber-reinforced polymer composites in the early 1940s, composite materials development was driven by the needs of space, defense, and aircraft industries where performance rather than cost was the prime consideration. At the beginning, conventional machining techniques were adopted to machine glass fiber-reinforced composites for convenience as well as to keep the capital costs down. This was followed by significant advancements in tool materials and tooling design. With the development of new and more challenging metal-matrix and ceramic-matrix composites, conventional manufacturing processes proved to be inadequate or even inappropriate to process them. Need and opportunity, therefore, exists for alternate nontraditional machining operations, such as laser machining, water jet (WJ) and abrasive water jet (AWJ) cutting, electrical discharge machining, ultrasonic-assisted machining, and electrochemical spark machining. When composites become more popular and are used in large volume in the civilian sector, such as auto and other consumer industries, material and processing costs will be the driving factors. A high degree of automation for the mass manufacturing of composite parts will be required to bring the costs down and compete with other materials. Advancements in the nontraditional machining processes offer an opportunity to process these materials economically, thus realizing the full potential of the composite materials. This paper gives a broad overview on the various issues involved in machining (conventional and nonconventional) of fiber-reinforced composites. The field of composites, in general, and machining of composites, in particular, are so broad that it would not be possible to do justice by discussing each aspect of composite material machining without ending up with a voluminous document. This review, therefore has to be limited to a few aspects of composite materials and their machining techniques. It may also be pointed out that in this review certain areas are dealt more in-depth than others. Personal preferences and availability of material in the open literature are some of the reasons for this nonuniformity in coverage. Also, some areas are more actively pursued than others. An attempt is made to highlight some of the issues and opportunities in the area of machining of composites.