Optimization for drilling process of metal-composite aeronautical structures

Abstract

Metal-composite laminates and joints are applied in aircraft manufacturing and maintenance (repairing) using aluminum alloys (AA) and glass fiber-reinforced polymer (GFRP). In these applications, drilling has a prominent place due to its vast application in aeronautical structures’ mechanical joints. Thus, this study presents the influence of uncoated carbide drills (85C, 86C, H10N), cutting speeds (v c = 20, 40, and 60 m min−1), and feed rates (f = 0.05, 0.15, and 0.25 mm rev−1) on delamination factor, thrust force ( F t {F}_{\text{t}} ), and burr formation in dry drilling metal-composite laminates and joints (AA2024/GFRP/AA2024). Experiments were performed, analyzed, and optimized using the Box–Behnken statistical design. Microscopic digital images for delamination evaluation, piezoelectric dynamometer for thrust force acquisition, and burr analysis were considered. The major finding was that the thrust force during drilling depends significantly on the feed rate. Another significant factor was the influence of the drill type (combined or not with feed rate). In fact, it was verified that the feed rate and the drill type were the most significant parameters on the delamination factor, while the feed rate was the most relevant on thrust force. The cutting speed did not affect significantly thrust force and delamination factor at exit ( F da S ) \hspace{.25em}({F}_{{\text{da}}_{\text{S}}}) . However, the combination f × v c was significant in delamination factor at entrance ( F da E ) \text{ }({F}_{{\text{da}}_{\text{E}}}) . Based on the optimized input parameters, they presented lower values for delamination factors ( F da E = 1.18 {F}_{{\text{da}}_{\text{E}}}=1.18 and F da S = 1.33 {F}_{{\text{da}}_{\text{S}}}=\hspace{.25em}1.33 ) and thrust force ( F t = 67.3 N {F}_{\text{t}}=67.3\hspace{.5em}\text{N} ). These values were obtained by drilling the metal-composite laminates with 85C-tool, 0.05 mm rev−1 feed rate, and 20 m min−1 cutting speed. However, the burrs at the hole output of AA2024 were considered unsatisfactory for this specific condition, which implies additional investigation.

Optimization of Cutting Parameters for Finish end Milling CFRP Under Vortex-Cooled Compressed Air

“…Initial studies approached the drilling of metal-composite stack 31 and CFRP 44 . While Devitte et al 31 studied the optimization of the drilling process, Hoffmann et al 44 evaluated the influence of VCCA on the quality of drilled holes. A study of the temperature in the drilling process was performed by Devitte et al 39 , which reported temperatures well below the degradation temperature for the tested conditions, with an analysis of SEM images indicating the absence of fiber deformation and matrix degradation.…”

“…Similar results were presented by Voss et al 18 , who also observed that larger clearance and rake tool angles improve the surface quality and reduce tool wear. Devitte et al 31 evaluated the influence of the cutting parameters and tool geometry in the delamination in Al-GFRP-Al hybrid stack drilling. The best results were achieved using lower v c , f, and a drill with a lower point angle, lower chisel edge, and higher rake angle.…”

Optimization of machining parameters in drilling of aluminium matrix composite (Al7050-12wt.% ZrO2) using Taguchi technique

“…The HSS drill bits used in this experiment was diameter of 6 mm, helix and point angle of 30 o and 118 o , respectively. The various factors, like 'v', 'f', and 'd', were taken into consideration as the input cutting variables based on the prior investigation [24,25], and their levels are shown in Table 1. According to the selection of parameters, L16 orthogonal array was most suitable design to conduct the drilling experiments and are depicted in Table 2.…”

A Review on Drilling of Multilayer Fiber-Reinforced Polymer Composites and Aluminum Stacks: Optimization of Strategies for Improving the Drilling Performance of Aerospace Assemblies

“…Both high localized temperature and thrust force are directly involved in this plastic deformation [91]. As depicted in Figure 4, two types of burrs, namely, uniform and crown, can be identified at the exit of a drilled aluminum plate, depending on workpiece material properties, drilling parameters and cutting forces [109,112]. As explained by Costa et al [113], entrance hole burrs are formed by the plastic flow of the material, while exit hole burrs are caused by the conformation of the material induced by high compression rates in the center of the hole.…”