Experimental Studies of the Holes Quality Parameters in Polymer Composite Materials

The subjects of study in the article are quality parameters, namely: geometric accuracy, roughness and shrinkage of holes in polymer composite materials (PCM) obtained by drilling. The study of quality indicators was performed with the help of drilling holes kinematic schemes in PCM. The methods used are the analysis of the quality indicators of PCM openings, the method of expert evaluations. The article deals with the analysis of the movement kinematics for the cutting wedge of the drill in relation to the placement of the PCM filler fibers. Experimental research was carried out on carbon fiber samples with 5 mm holes. Drilling was performed with different types of drills: spiral standard drills P6M5K6 and carbide drills with undercut cutting edges BK8. Measurements of accuracy, roughness, fluffiness and shrinkage of holes were carried out on Faro Fusion Arm, Arbus MP-7 devices and a Zeis Tvoxyp-450 scanning electron microscope. The following results were obtained. According to the analysis and synthesis, the existence of cyclic zones of cutting change, which affect the quality parameters for the machined surface of the holes, was established. The fractographic features of PCM fiber destruction after the drilling process are shown. It was found that when PCM is processed with P6M5K5 drills, the roughness of the holes is lower than when processed with BK8 drills. BK8 drills with an undercut cutting edge have an advantage over P6M5K5 drills. It has been proven that BK8 drills allow to increase strength in point joints of PCM parts by up to 20%. The dependence of the shrinkage for the hole in PCM on the cutting modes was experimentally confirmed. The results of the research are intended for a wide range of users who specialize in the mechanical processing of PCM when using innovative structural and multi-functional materials.