Study of Tool Condition Monitoring during Drilling of CFRP\Ti Stacks under dry and wet Conditions (original) (raw)
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Applied Sciences
Composite material parts are typically laid out in near-net-shape, i.e., very close to the finished product configuration. However, further machining processes are often required to meet dimensional and tolerance requirements. Drilling, edge trimming and slotting are the main cutting processes employed for carbon fiber-reinforced plastic (CFRP) composite materials. In particular, drilling stands out as the most widespread machining process of CFRP composite parts, chiefly in the aerospace industrial sector, due to the extensive use of mechanical joints, such as rivets, rather than welded or bonded joints. However, CFRP drilling is markedly challenging: due to CFRP abrasiveness, inhomogeneity and anisotropic properties, tool wear rates are inherently high leading to superior cutting forces and detrimental effects on workpiece surface quality and material integrity. Damage such as delamination, cracks or matrix thermal degradation is often observed as the result of uncontrolled tool w...
Journal of Manufacturing and Materials Processing, 2019
The use of lightweight material such as CFRP/Ti6Al4V in stacked structures in the aerospace industry is associated with improved physical and mechanical characteristics. The drilling process of nonuniform structures plays a significant role prior to the assembly operation. However, this drilling process is typically associated with unacceptable CFRP delamination, hole accuracy, and high tool wear. These machining difficulties are attributed to high thermal load and poor chip evacuation mechanism. Low-frequency vibration-assisted drilling (LF-VAD) is an advanced manufacturing technique where the dynamic change of the uncut chip thickness is used to manipulate the cutting energy. An efficient chip evacuation mechanism was achieved through axial tool oscillation. This study investigates the effect of vibration-assisted drilling machining parameters on tool wear mechanisms. The paper also presents the effect of tool wear progression on drilled hole quality. Hole quality is described by ...
Parametric Study and Process Monitoring on Drilling of CFRP Composites
2017
Carbon fiber reinforced plastic (CFRP) composite materials are finding huge applications in many industries due to their excellent properties i.e., high strength to weight ratio and corrosion resistance. Drilling of CFRP composites is required for assembly of these composites structures in aerospace industry. The present work focuses on investigation of the feasibility of drilling CFRP composite using drill bit made of tungsten carbide (WC) of diameter 10 mm and varying point angle under dry cutting conditions. The CFRP composite was fabricated using woven carbon fiber by hand lay-up technique having quasi-isotropic configuration i.e. fiber orientation of [0/90/45/45]. This study involves online monitoring of thrust force and torque using dynamometer and providing a deep understanding of the relationship between hole quality and process parameters. The damage caused at the entrance of the drilled hole is characterized by delamination factor, circularity and surface roughness, which ...
Vibration assisted drilling of CFRP/metal stacks at low frequencies and high amplitudes
Production Engineering
In many applications of automotive and aircraft industries the use of material combinations such as compound materials made from carbon fiber reinforced plastics (CFRP) and metal materials like steel, titanium or aluminum alloys is significantly increasing. For these industries, the lightweight and mechanical properties of the reinforced plastic materials gain more and more importance. When machining material combinations, a number of distinctive material related effects occur and hamper the straightforward implementation of machining processes. These effects mainly derive from the distinctive chipping behavior of the material combination caused by the different material characteristics. Thus, the drilling process of CFRP/metal stacks is to be regarded as a challenging task due to the requirements of machining efficiency and quality aspects. In this regard, vibration assisted drilling at low frequencies but high amplitudes opens up significant opportunities for improvements of the machining processes. The feed rate is superimposed by a controlled harmonic motion in order to create an intermittent cutting state. The potential of vibration assisted drilling lies in the reduction of cutting forces and tool wear.
Procedia Engineering, 2013
Composites are used in conjunction with another material to form a multi-material stack-up, which results in greater strength to weight ratios. In a wide range of aerospace applications dissimilar material stack-ups of composites and aluminium and/or titanium are used. Drilling is probably the most common machining operation applied to composites since components made out of composite materials are usually near net shaped and require only holes for assembly integration. In this investigation, experiments were conducted by varying the drilling parameters and determining the optimum cutting conditions for drilling of CFRP/Ti stacks using Genetic Algorithm (GA) optimization technique. Tool wear study was performed by drilling 100 holes each with 118° and 130° point angle drills. Less progressive tool wear and better chip evacuation was achievable in 130° point angle drills when compared with 118°point angle drills.
2017
Drilling through Carbon Fibre Reinforced Polymer (CFRP) / Titanium (Ti) stacks is important for mechanical assembly of aircraft, however, there are concerns over rapid tool failure and part damage, which lead to reduced productivity and hole quality. Limited research has shown that Ultrasonic Assisted Drilling (UAD) has potential to improve hole quality when drilling CFRP and Ti individually. This has attracted the attention of aircraft manufacturers to evaluate the performance of UAD for CFRP/Ti stacks applications. This thesis presents three main studies of experimental work, which investigate tool wear mechanisms that govern tool life and hole quality when drilling CFRP/Ti stacks in a single continuous operation (one-shot) using carbide (WC-Co) drills. Study 1 involved conventional drilling of CFRP/Ti stacks as opposed to drilling CFRP and Ti individually using constant cutting parameters (cutting speed = 50 m/min; feed rate = 0.05 mm/rev). Study 2 and 3 investigate the effect of...
Drilling of titanium/CFRP/aluminium stacks
2010
Following a review on the machinability of CFRP composites and multilayer stacks typically comprising metallic and composite material elements, the paper details experimental results when drilling 30 mm thick titanium/CFRP/aluminium workpiece stacks. Testing utilised a modified fractional factorial design based on an L18 Taguchi orthogonal array. This comprised four factors, three of which were at three levels and one at two levels and involved tool coating, cutting speed, feed rate and machining environment. Tools evaluated involved hardmetal and diamond coated carbide in addition to uncoated tungsten carbide drills. Response variables were principally tool wear and cutting force/torque with an end of test criteria of 300µm flank wear. Peeling of the CVD diamond coating occurred within the first several holes drilled however this was not a limiting factor in terms of tool life. Principal damage occurred when drilling through the titanium (Ti-6Al-4V) rather than the aluminium (Al 7050) or CFRP (unidirectional "UD" laminates) sections. Best tool life/performance (310 drilled holes) was obtained with the more conventional uncoated carbide drills at lower cutting speed and feed rate. Typically thrust forces increased from 300 N for the first hole to ~2200 N for last hole drilled while torque values were generally below 600 N.cm for worn tools.
Quality monitoring and control for drilling of CFRP laminates
Journal of Manufacturing Processes, 2019
Widespread uptake of Carbon Fiber Reinforced Plastics (CFRP) in the aerospace and automotive industries over the past two decades has highlighted the importance of machining composites in large production environments. The abrasive nature of carbon fibers and inherently heterogeneous structure of CFRP laminates create tool wear conditions that are unlike those typical of metal machining. The present work quantifies thrust force, tool flank wear and push-out delamination (POD) for drilling of 8 mm thick CFRP laminates with 8 mm high-speed steel drill bits. Thrust force, directly responsible for delamination effects, is found to increase with feed rate and cutting speed, while flank wear increases at lower feed rate and higher cutting speed. POD is found to increase with feed rate and tool wear, with excessive values of the latter found to change the material removal mechanism from cutting to tearing of fibers resulting in increases in local workpiece temperature and matrix degradation. A quality monitoring and control strategy for drilling of CFRP laminates is then proposed based on these observations by exploiting a fuzzy logic algorithm to predict POD based on thrust force and flank wear measurements. Feed rate, in turn, is controlled based on the POD to ensure acceptable machining quality over the entire lifespan of the tool. The developed approach offers an effective and simple way of maximizing throughput and tool duration while guaranteeing part quality.
The International Journal of Advanced Manufacturing Technology, 2013
This paper aims to establish the wear mechanisms of coated and uncoated tungsten carbide drills when drilling carbon fibre reinforced plastics (CFRP)/aluminium alloy (Al) stacks. During the drilling experiments, thrust forces were measured. A scanning electron microscope (SEM) and a numerical microscope, provided with a scanning device, were periodically used to analyse tool wear mechanisms and to measure wear progression of the tool cutting edges. For both coated and uncoated drills, abrasion was the dominant tool wear mechanism, affecting the entire cutting edges. Higher wear was observed on uncoated tools which caused a significant increase in thrust force during drilling both Al and CFRP materials. The influence of these phenomena on the quality of the holes and on the generated roughness was also discussed.
2021
In this paper, the tool wear mechanism in low-frequency vibration-assisted drilling (LF-VAD) of carbon fiber reinforced polymer (CFRP)/Ti6Al4V stacks has been proposed using variably machining parameters. Based on the kinematics analysis, the effect of vibration amplitude on the chip formation, uncut chip thickness, chip radian, and axial velocity was presented. Subsequently, the effect of LF-VAD on the cutting temperature, tool wear, delamination, and geometrical accuracy was presented for different vibration amplitude. The LF-VAD with the utilization of minimum quantity lubricant (MQL) resulted in a successful drilling process of 50 holes, with a 63 % reduction of the cutting temperature. For the rake face, LF-VAD reduced the adhered height of Ti6Al4V by 80 % at low cutting speed and reduced the crater depth by 33 % at the high cutting speed. On the other hand, LF-VAD reduced the flank wear land by 53 %. Furthermore, LF-VAD showed a significant enhancement on the CFRP delamination...