Research On Boring Carbon Fiber Reinforced Composites

The carbon fiber reinforced plastics (CFRP) are made by the soft resin matrix with strong carbon fiber reinforcement. They have much good characteristics, such as high specific strength, high specific modulus, good fatigue performance and high heat resistance and so on, which have been widely used in aeronautics, astronautics and automotive etc. However, because there is a big difference between matrix and reinforcement of the physical characteristics, mechanical properties of CFRP is anisotropic and interlaminar strength is low, it is easy to produce defects such as delamination and tear when machining. CFRP is typical of difficult materials. In view of this, some studies are conducted in this paper:(1) Proceed from the cutting model of unidirectional carbon fiber composite, the chip formation process in the different fiber angle θ and the impact of fiber angle on the surface roughness were analyzed. When0is between0°and90°, the surface processing quality is good; while0is between90°and180°, the surface processing quality is poor.(2) Experiments were carried out by using PCD tool to bore CFRP and the influence of cutting parameters on cutting force and hole exit tear factor (the ratio of tear size and hole diameter) was studied.Besides, this essay also compared the PCD tool with cemented carbide tool(YG6X) on processing quality. The results showed that cutting forces increase along with the increasing of the cutting parameter; tear factor has almost independent on cutting depth, but there is a linear positive correlation between the factor and feed rate; when increasing the cutting speed the value of tear factor showed a tendency to decrease and then keep essentially constant; improving the cutting speed can properly reduce the degree of hole export tear; compared with carbide YG6X tool, using PCD tool can get a better processing quality when machining CFRP.(3) The geometry parameters of PCD tool were optimized by orthogonal test and the reasonable parameters are as follows:rake angle yo is15°， main deflection angle Kr is between40°and45°, assistant deflection angle Kr’is8°, relief angle α0is between5°and7°. and the tool nose radius rε is between0.2mm and0.4mm. (4) Through X-R analysis, the main impact factors on hole exit tear factor are tool nose radius, followed by relief angle, finally the main deflection angle and assistant deflection angle; the main impact factors on surface roughness are main deflection angle, followed by relief angle and assistant deflection angle, finally tool nose radius.(5) Through the tests of PCD tool boring CFRP, this processing technology proved to be able to achieve the level of traditional drilling and grinding basically. When the larger diameter hole is needed and the precision is not very high, we can consider using PCD tool to bore CFRP, which not only guarantees the processing quality, but also improves efficiency.