INCREASING THE QUALITY OF DRILLING HOLES IN FIBER REINFORCEMENT COMPOSITE MATERIALS

Abstract

Problems. Fiber reinforcement polymer composite materials (FRP) are used in many areas of modern machine building, mostly in aircraft and aerospace industries. Millions of high-quality holes in FRP details are necessary for production of a modern passenger aircraft, to provide reliable bolt and rivet connections. Drilling is a key-machining operation for the production of holes in FRP.Comparing metal-containing materials drilling, FRP drilling is accompanied by the appearance of specific defects, such as delamination, uncut fibers, the damages of FRP’s matrix from the holes surface and thermal destruction. The listed defects adversely affect the reliability of bolt and rivet joints between parts of FRP, which determines the relevance of this study.The aim of the study. Determination of the influence of the support cutting edges of the developed drill with superhard materials on the holes surfaces quality of carbon fiber reinforcement plastics (CFRP) samples.Research methodology. The goals were achieved by experimental investigations on drilling CFRP samples by the designed drill bits and drill bit from SECO (Sweden) with similar cutting conditions. The drilling process was accompanied by the registration the axial force of cutting, torque and the acoustic emission signal. The analysis of the registered signals allowed to study the features of support cutting edges of the developed drill. The quality of the drilled holes surfaces was analyzed by determining the roughness using Alicona Infinite Focus (Austria) optical microscope. Conclusions were made according to the results of experimental studies.Conclusions. Analyzed data are shown, that the developed drill provides twice the lower roughness of the holes surfaces than the drill SECO, according to the same level of the wear of the main cutting edges. These results are mainly due to the work of the support cutting edges of the developed drill on a reversing feed.