مقاله انگلیسی رایگان در مورد قابلیت ماشینکاری فیبرهای پلیمری تقویت شده – الزویر 2018

The demand for carbon fiber-reinforced plastic (CFRP) is increasing in the aerospace industry, due to its light weight and high specific strength and elastic modulus. With annual growth in the aerospace and defense market projected to be around 14%, the demand for CFRP is expected to total 23,000 tons by 2020 [1]. CFRP products usually must be machined during the trimming process. Abrasive water jet and milling are the trimming methods currently used, but these have disadvantages regarding cost and efficiency. Abrasive water jet (AWJ) machining is suitable for CFRP cutting because it inflicts low thermal damage and imposes little mechanical stress on the workpiece. On the other hand, the disadvantages of AWJ machining include high equipment cost and the necessity of elaborate microfiltration before disposal of water. Moreover, conventional machining techniques do not work on composites like metals do, due to the composite structure, which consists of very strong fibers interwoven into a softer matrix [2]. Therefore, the effect of the AWJ process parameters on cut quality remains a target of study in engineering [3][4]. Milling is also commonly used for the trimming process, but is associated with a high cutting-tool wear rate and the potential for fiber delamination. Hanasaki et al. [5] studied the tool wear mechanism in CFRP machining. Although tool-wear characteristics are different for CFRP and GFRP due to the difference in fiber elastic modulus, the fundamental tool-wear mechanism is similar. In the case of cutting graphite or epoxy composite, the elastic energy of the deformed fibers is released after the fibers are severed, imparting a thrust force on the tool flank and providing a potent source of tool wear [6][7]. Moreover, Kaneeda et al. studied chip formation and reported that CFRP cutting results in three types of chip formation: delamination, fiber buckling, and fiber cutting type. They are determined by the fiber angles and tool-rake angles [8]. In terms of delamination as a defect of the machined surface, increased feed per tooth increases its likelihood [9]. On the other hand, laser cutting and electrical discharge machining (EDM) are studied as substitutes of these conventional machining processes. As both of the laser cutting and EDM are the thermal process, machining force doesn’t act and then the delamination can be avoided and there is no tool wear. However, several problems are caused by the difference in thermal properties and light absorption characteristics between carbon fiber and matrix resin. For example, the matrix resin is excessively removed and a large heat affected zone (HAZ) is generated [10][11][12]. To solve these problems, Takahashi et.al.[13] reported that UV laser, which has higher absorption rate to the epoxy resin, can achieve high quality cutting. Wolynski etl.al. [14] similarly reported on HAZ using a high power picosecond pulsed laser system with varying laser wavelength. There is a trade-off relationship between machining efficiency and accuracy on laser cutting. As for the EDM, the delamination can be avoided because machining force doesn’t act, but the machining efficiency for CFRP is much lower than that of milling and AWJ machining.