Some Researches On Drilling Carbon Fiber Reinforced Composites

Carbon fiber reinforced plastics (CFRP) are characterized by low weight, superior strength-to-weight and stiffness-to-weigh ratios, low expansion coefficient, high fatigue strength, good thermal shock, high heat resistance and well vibration absorption. They have been used widely in airplanes, spaceships and automobile etc. But the dynamics characteristics of CFRP in each direction are different and the condition of machining is hard, the strength between the layers is low, it's easy to produce delamination and avulsion under the force of cutting while machining, and it even will be worse when drilling. CFRP is a typical difficult-to-machine composite, and the quality of machining is difficult to guarantee.By focusing on the characteristic of difficult-to-machine of CFRP, this paper is mainly conducted to study several things as followings:1) Introduced a drilling model which is built based on the analyze on various disfigurements of CFRP when drilling; set binary cutting of CFRP for a example, based on the analyze that CFRP made the deformation and formation of the chips when machining process, by focusing on one kind of deformation reached a theoretical derivation on cutting force of binary cutting, and made a theoretical derivation on axial force which came from the process of diamond tools drilling, deduced the equation of the cutting force in the process of drilling and indicated the relationship between the axial force and the drill parameters; according to the feature of CFRP disfigurements, two kinds of new methods for evaluating the limitation of burr and avulsion were brought out: length ratio and area ratio; and also some suitable suggestions were shown for high quality drilling.2) By focusing on the problems of having more disfigurements when drilling CFRP in traditional way, new process study of "grinding instead of drilling" was carried out, and developed super-hard electroplated abrasive drill; introduced a drilling model which indicates why there are no disfigurements when drilling CFRP by super-hard electroplated abrasive drill, and compared with the traditional ways, more higher quality machining effects were gained; investigated the abrasion rule of the super-hard electroplated abrasive drill, a useful conclusion that super-hard electroplated abrasive drills have longer life-span, and be more efficiency and economical was reached depending on the comparison experiment between sintered-carbide drill and super-hard electroplated abrasive drill.