Machining of Composite Materials: Mechanics, Quality and Coolant Strategies

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Composite materials have received considerable research and development due to wide spread demands in different industry.  Metal Matrix Composites ( MMC) have been widely utilized in many applications including automotive and aerospace since the early trials by Toyota in the early 1980s. MMCs offer several advantages including higher specific strength and stiffness, weight reduction, better resistance to wear and impact damage, a lower thermal coefficient of expansion, tailorable thermal conductivity, and better vibration damping.  In comparison to conventional metal alloys, MMCs offers lower life-cycle costs and replace some critical or strategic materials. MMCs are intended to substitute monolithic materials including aluminium alloys, ferrous alloys, titanium alloys and polymer based composites in several applications. In order to have a wide spread MMCs substitution for monolithic materials in engineering system, efforts have been made to produce MMCs by casting, or hot forging. However, the generated near net-shape products still have to be machined into the designed shape and dimension. Intensive research to investigate the machinability of the MMCs was conducted earlier, including the research performed by the applicant during the past few years. A previous work of the applicant and a review of the published literature indicate that the conventional cutting of these materials leads to excessive tool wear and possible subsurface damage, thereby resulting in increased cutting cost and production time. Subsurface damage assessment is critical for machined components subjected to fatigue, especially in critical application such as aerospace. In view of the growing applications of these materials, detailed study of their machined surface integrity and improving of their cutting process efficiency is required. In addition, detailed information about the reinforcement's interaction during the metal removal and how it affects the machined surface integrity is required. In view these needs, this study will focus on challenges associated with machining MMCs including surface integrity issues. Also, the use of new nano-fluid with Minimum Quantity Lubrication (MQL) will be explored and developed.  The role of nano-additives in improving lubrication and heat characteristics will be studied.  The nano-fluid based MQL is a new technology which was recently explored by the applicant for machining aerospace alloys including titanium and  inconel .  The successful use of this technology during machining MMCs will with no doubt facilitate the wide spread applications of MMCs and present the nano-fluid based lubricant not only as effective lubricant but also as a sustainable environmentally friendly technique when it is utilized with MQL.