Research On Precision Hole Making Process For Laminated Materials Of Aircraft Panel

To meet the dual demands of an aircraft's lightweight and structural performance, composite materials and laminates composed of metal materials(aluminum and titanium) have been widely used in aircraft wings and tail components, etc. The quality of connecting holes has direct relation with the strength, stiffness and safety of the connection. This paper focuses on the development needs of aircraft automated assembly, and takes the breakthrough of the technology bottleneck of automatic drilling aviation laminates as the goal, with the defects and its forming mechanism of drilling laminated materials as the penetration point and the laminates of CFRP/Al as well as Al/Al as the research object. The inner connection between hole quality, burr height and cutting force is revealed by the theoretical modeling and experiments.The main research contents in this paper are as follows:(1)The forming mechanism of composites delamination was analyzed, and the primary reason for delamination is that the thrust force loading on uncut material is beyond the interlayer shearing strength of the composites. The order of the laminate stacks influence on thrust force was analyzed using the concept of critical thrust force, then different distribution models of thrust force was established, and finally the critical thrust force model was obtained based on the delamination, which was verified by experiments. The fitting formula of thrust force was established based on the cutting parameter, which could provide a good basis for choosing processing parameters.(2)The research of interlayer burr between metal laminates in this paper focused on the mechanism, and the gap model between laminates was established using the plate theory and superposition principle, and the relation between the gap and the interlayer burr height was verified. The influence of plate size, position, processing parameters and pressing force on the gap between laminates was summarized, based on which pressure foot was used to restrain the burr between gaps, and recommended clamp force could be given based on different conditions.(3)The qualitative or quantitative analysis was carried out for aperture, roundness, roughness of hole surface, interlayer burr and thrust force in CFRP/Al laminate drilling. The influence of tool structures and process parameters on the accuracy of holes drilling was discussed using experiments, and the hole quality and efficiency was improved by optimizing process parameters and paths. Finally, the influence of diamond coated drill's wear morphology and mechanism on the cutting progress was analyzed to predict the tool life.In this paper, key problems in the automatic precision drilling were analyzed, and related modified strategies were proposed. The research results will provide useful supplement for theoretical system of holes drilling, which has important scientific significance and engineering applicable value.