Abstract
An experimental study on drilling of carbon fiber–reinforced plastic/titanium alloy was conducted using three kinds of drills to investigate the cutting process. This research was mainly focused on the drilling forces, drilling temperatures, chips, and delamination area with respect to the cutting parameters and tool geometries. One type of tungsten carbide twist drill and two types of chemical vapor deposition diamond-coated drills which were multi-facet drill and brad spur drill, respectively, were used in this research. The influence of drilling parameters and tool geometries was analyzed and the conclusions were drawn that the proper selection of drilling parameters and drill geometries could lead to better hole quality. Experimental results indicated that the drilling forces and hole quality have a strong connection with feed rate while the impact of cutting speed is small. Research results also showed that the use of multi-facet drill could reduce the delamination greatly and thus produced a better surface integrity. Besides, drilling temperature and titanium alloy chips were studied in this research.
Highlights
Carbon fiber–reinforced plastics (CFRPs) are widely used in aeronautic and aerospace engineering owing to their characteristics of light weight, high specific strength, high specific stiffness, good fatigue resistance and corrosion resistance, and designability.[1,2] Being the final link of aircraft structure assembly, drilling is the most frequently used process in composite materials machining
Many authors have proposed that the delamination in carbon/epoxy machining is closely related to thrust forces which mainly depend on cutting parameters and drill geometry.[8,9]
To evaluate the drilling force under same criteria and eliminate influence from CFRP/Ti boundary, all the values of drilling force were only taken from the stable interval in each drilling process, which was from bit wholly engaged till drill tip almost exiting, and the drilling force values were the average values of these stable intervals
Summary
Carbon fiber–reinforced plastics (CFRPs) are widely used in aeronautic and aerospace engineering owing to their characteristics of light weight, high specific strength, high specific stiffness, good fatigue resistance and corrosion resistance, and designability.[1,2] Being the final link of aircraft structure assembly, drilling is the most frequently used process in composite materials machining. Fiber pull-out and matrix degradation can be observed on the holes after drilling These defects in drilling fiberreinforced composites may lead to deterioration of the structure strength as well as poor assembly accuracy.[4] it is hard to control the machining quality in drilling process of CFRPs. Stacked composites of CFRP/CFRP, CFRP/Al, and CFRP/Ti are widely used in aircrafts such as Boeing 787 and Airbus A380.5 In the final assembly step of aircraft manufacturing, 60% CFRP components are scrapped for their drilling delamination.[6,7] Many authors have proposed that the delamination in carbon/epoxy machining is closely related to thrust forces which mainly depend on cutting parameters and drill geometry.[8,9] In drilling process, different cutting parameters, such as cutting speed and feed rate, lead to different thrust forces and torques, affecting the quality of drilling holes.[10,11,12] delamination can be avoided effectively if the cutting forces generated can be kept lower than the critical thrust force by optimizing tool geometry and processing techniques, which are essential for achieving highquality hole
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