Formation of the quality of holes obtained by drilling in aviation structures made from polymer composite materials

Abstract

The subject of this study is the quality indicators (geometric accuracy, roughness, cylindricity and taperness) of holes obtained by drilling in aircraft structures (AS) made of polymeric composite materials (PCM). The quality indicators of holes in AS made from PCM were studied by using kinematic schemes across and along the direction of drilling. A kinematic scheme of formation of the predicted surface roughness of the hole in AS made from PCM has been built. The calculation of the predicted roughness of PCM holes taking into account the geometry of the drill and drilling modes has been proposed. Experimental studies have been implemented to establish the parameters of predicted roughness, geometric accuracy, taperness, as well as deviations from cylindricity. The methods used were the method of expert assessments and experimental studies of quality indicators of PCM openings. The following results were obtained: the roughness in full-scale experiments turned out to be lower than the theoretical calculated values with a difference of not more than 10...15 %. It was found that roughness, taperness, deviations from geometric precision and cylindricity differ in characteristic rotation zones of the drill from 0° to 360° and depend on the drilling parameters and PCM properties. It was found that the deviation from the hole cylindricity is affected by the shrinkage of the material. The appearance of ovality in the holes of prototypes was established. The results of experimental studies of measurements of hole diameters to establish deviations from cylindricity, geometric accuracy, and taperness met the production requirements for the accuracy of their manufacture. For geometric precision and deviation from cylindricity, the results ranged from 7 to 12 IT grades, and for taperness, from 0.083 to 0.28 % per a hole in AS made from PCM and 9–10 IT grades