| Carbon-Titanium Laminate (abbreviation:CTIL) is refers to the carbon fiber composite sheet and titanium alloy sheet laid alternately. In the process of which the materials were widely used in aerospace industry, they need a lot of holes of riveting and assembly, and the quality requirements for the holes are very high. Because the processing quality of the hole have a significant relationship with the mechanical properties of material in the position of hole of riveting and bolt connection. Besides, as a result of that the material properties is special, such as poor heat transfer performance, high hardness, bad machining performance, making tool wear rapidly. According to the above problems, quantity of theoretical analysis and experimental research method were used to study the chip morphology, cutting temperature, thrust force, the quality of the hole and tool wear of CFRP/Ti interlaminar hybrid composite materials drilling, the conclusions gained as following.1.Because of the fiber angle is different, there are three forms of chip formation during the process of drilling single CFRP, they are the separation between the layers, interlayer sliding and bending shear respectively. The chip of the separation between the layers and bending shear are massive, the chip of interlayer sliding is fibrous. Mechanism of chip formation of titanium alloy can be mainly divided into two parts:the extruding of the chisel edge and the cutting of the main cutting edge. The shape of chip is commonly long and spiral. The cutting parameters (cutting speed, feed rate, cooling temperature, the shape of the drill, drilling direction) has a certain influence on chip morphology, The faster cutting speed and the slower feed rate, the thinner the thickness of the chip, the more easy to occur the phenomenon of tangles tool, meanwhile, as a result of the time of the friction of tool between materials growing, making the cutting heat increasing, temperature rising, and easy to achieve the ignition point of titanium alloy600℃, making the phenomenon of chip combustion to occur. The impact of cooling temperature chip morphology, on the one hand, the higher the cooling temperature, the less drilling heat would be taking away, the temperature of drilling area would be higher, chip was easy to oxidation, and cockle appeared on the surface of the chip; on the other hand the higher cooling temperature, the greater the cold air emission, the chip is easy to broken. The impact of drilling sequence order on chip morphology is that when the drilling sequence order is Ti-CFRP, the chip of Ti is long and spiral. And when the drilling sequence order is CFRP-Ti, as a result of the effect of the friction between chip and hole wall, clearance groove of tool, making the chip to be twisted together and easily to broke.2.Thrust force:the higher the cutting speed, the slower feed rate, the lower the cooling temperature, the smaller the thrust force. When the drilling sequence order is Ti-CFRP, the thrust force of each stage is minimal with the drill b, second drill c, maximum with drill a. The influence of drilling sequence on the thrust force of each stage is small. The primary and secondary relations about the impact of various factors on thrust force through orthogonal experiment analyzing is that the shape of the drill, cooling temperature> cutting speed> feed rate, through the orthogonal experiment analysis of variance, it gained that during the process of drilling Ti, the shape of the drill, cooling temperature and cutting speed had a significant influence on thrust force, and during the process of drilling carbon fiber composite material, only the cooling temperature had a significant influence on thrust force.3.The aspect of drilling temperature:(1) observing the process of drilling with infrared thermal imager, received that no matter how the drilling sequence, the highest temperature concentrated the part of the drill at the entrance of hole;(2) with the cutting speed increasing, drilling temperature ascended significantly;(3) the feed rate has little effect on drilling temperature, with the feed rate increasing, cutting temperature changed very gentlemanly, but the general trend was decreasing;(4) when cooling temperature is lower, the drilling temperature will be lower, especially just after adding the cold wind (cooling temperature is11℃), drilling temperature changed more obviously, had fallen nearly100℃, then the trend of drilling temperature changing slowing.4.The situation of the quality of the hole when the material of drilling out and drilling in is CFRP and Ti respectively. CFRP as the material of drilling out, the defects of exit are generally burrs, avulsion, delamination; as the drilling in materials, the quality will be improved, but also had the phenomenon of small burrs and cleavage to occur. Titanium alloy materials as the dilling out material, the most common defect is flanging; as the dilling in material, in the condition of tool wear or unreasonable making hole way, burr had the possible to appear. In addition, the results showed that carbon fiber composite material as the drilling out material, the higher the cutting speed, the lower feed rate, even the lower the cooling temperature, could effectively improve the exit quality of the hole, reduce the size of the burr, reduce the phenomenon of avulsion and cleavage to occur. Variable parameters, moreover, the cutting speed was improving during drilling CFRP, drilling and reaming had a repairing effect on initial defects, making the exit quality was better; Spiral milling hole, although the exit quality was good, but the drilling in material was titanium alloy, it’s easy to have a burr.5.Tool wear:(1) the forms of tool wear had chip adhesion, peeling of major flank, tipping;(2) through the experiment, gained that with the number of drilling holes increasing, the quantity of tool wear increased, when the number of the holes was40for the drill a, the quantity of tool wear had reached to0.133mm,when the number of the holes was reached45, serious collapse phenomenon of drill had occurred, so in order to improve the quality of subsequent hole processing, should be timely replacement of the new tool. |
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