Drilling Of Carbon Fiber Reinforced Plastics Research Articles

Multimodal 1D CNN for delamination prediction in CFRP drilling process with industrial robots

There is a growing demand for carbon fiber-reinforced plastics (CFRPs) in the aerospace and automotive industries. Consequently, the assembly and repair of CFRP components has garnered considerable attention. However, at industrial sites, there are potential difficulties in the CFRP drilling process. These challenges arise from the anisotropic properties of CFRP and the limitations of using an optical microscope to assess the quality of millions of drilled holes. Therefore, this study introduced an advanced indirect prediction method for the CFRP hole quality based on multisensor data. During the drilling process, data including force, torque, acceleration, voltage, current, sound, and images of the hole exits were acquired via a robotic machining system. The delamination factors, Fd and Fa, which quantify the quality of the hole, can be calculated from the hole images. Preprocessing was employed to segment the sensor data into discrete drilling trials and extract spectral features from the data. This paper proposed a multimodal one-dimensional convolutional neural network (1D CNN) that predicts delamination factors from time series multi-sensor data. A case study, using a test set of 100 trials, validated the proposed model. The performance of the proposed model was evaluated by the mean squared error (MSE) and inference time, yielding 8.42 ± 0.167 × 10−2 and 3.48 ± 0.192 s for Fd, and 6.1 ± 0.729 × 10−2 and 3.13 ± 0.098 s for Fa, respectively, across the entire test set with 100 trials. This result exceeds those of previous studies in terms of both the MSE value and inference time for multimodality, emphasizing the predictive accuracy and real-time operational capabilities of the proposed model in industrial settings. Furthermore, this approach provides practicality and flexibility, facilitating the easy integration or removal of sensors through data-driven preprocessing and a multimodal learning scheme.

Investigation on carbon fiber-reinforced polymer combined with graphene nanoparticles subjected to drilling operation using response surface methodology and non-dominated sorting genetic algorithm-II

In this article, drilling of carbon fiber-reinforced plastics combined with graphene nanoparticles is investigated. These nanocomposites have the potential to be used widely in different industrial applications such as electrical, biomedical and aerospace engineering due to their superior mechanical and thermal specifications. Nonetheless, to be assembled on different sets, drilling nanocomposites is required especially for rivets and joints. In drilling carbon fiber-reinforced polymers (CFRPs), delamination is one of the main challenges that should be minimized in order to enhance the produced hole quality. Besides, machining force is a chief factor to control the drilling-induced damages, especially delamination. This article evaluates the effects of machining parameters on machining force and delamination using response surface methodology experimental design and non-dominated sorting genetic algorithm-II (NSGA-II) multiobjective optimization methodology. Examining delamination is conducted in two parts including peel-up and push-down delamination which are the principal drawbacks in drilling of fiber-reinforced composites. Analysis of variance is also carried out in order to examine the effects of the machining parameters. In addition, predictive quadratic correlations are established by regression analysis. Eventually, multiobjective optimization was implemented by NSGA-II and the optimal values were obtained from pareto-optimal solution set aimed at enhancing the drilling process.

Machinability of CFRP/Ti6Al4V stacks with low-frequency-vibration assisted drilling under different cooling strategies

Carbon fiber reinforced plastic (CFRP)/Ti6Al4V stacks are widely used in the aircraft industry, and drilling these stacks is essential during the assembly process. To solve the problem of high drilling temperatures in CFRP/Ti6Al4V stacks, which lead to poor tool life and hole quality, the effects of three cooling strategies compose minimum quantity lubrication (MQL), water-based coolant, and internal air cooling, were investigated in this study. Tensile/compressive strength and fatigue-life tests were conducted to evaluate the applicability of the cooling medium before drilling. Then, low-frequency vibration-assisted drilling of CFRP/Ti6Al4V stacks was performed to investigate and analyze their machinability under the three cooling strategies by analyzing the drilling temperature, thrust force, tool wear, chip removal capacity, and hole quality. The results show that the selected cooling media, including Rhenus XT46 and Accu-Lube LB2000, are applicable in CFRP drilling, whereas the adopted media, compared with water, have little influence on the tensile/compressive strength and fatigue life of the CFRP. Compared with internal air cooling and MQL, water-based coolant can more effectively improve the machinability of CFRP/Ti6Al4V stacks, decreasing the CFRP drilling temperature by 41.6 % and 40.1 %, respectively, while the reductions in the Ti6Al4V drilling temperature are 76.7 % and 57.4 %, respectively. Meanwhile, under water-based coolants, the thrust force reductions in the drilling of CFRP are 13.1 % and 11.7 %, whereas those in the drilling of Ti6Al4V are 11.0 % and 7.8 %, respectively, compared with the internal air and MQL. In addition, under the water-based coolant condition, the tool wear rate is the slowest and the hole quality is the best among the three cooling strategies, whereas a high injection pressure further decreases the VBmax value. Furthermore, under the water-based coolant conditions, the Ti6Al4V exit burr height and CFRP exit delamination are the lowest. These findings provide useful insights into improving the machinability of CFRP/Ti6Al4V stacks in the aerospace industry, particularly for drilling that requires high-quality holes and a long tool life.

The effects of support plate thickness on the drilling machinability of CFRP

When carbon fiber reinforced plastics (CFRP) are drilled, delamination damage occurs at the hole entry and exit. An important method to reduce delamination at the hole exit is using a support plate. Therefore, sustainable drilling of CFRP to reduce the delamination damage is promising for modern industries. In this study, the effect of drilling CFRP composite plates using support plates of different thicknesses on thrust force, delamination, and borehole surface quality was experimentally investigated. The results showed that the thrust force increased as the support plate thickness increased at low spindle speed, but the support plate thickness did not significantly affect the thrust force at high spindle speed. While severe delamination damage occurred at the hole exit in the tests without the use of support, delamination damage was significantly reduced in the case of using a support plate. On the other hand, the severity of the damages decreased as the support plate thickness increased, especially unless very high feed rates were chosen. Consequently, the thickness of the support plate considerably influences the damage formation and severeness of the damages is significantly reduced when a support plate with sufficient thickness is used.

Smart Tool Wear Monitoring of CFRP/CFRP Stack Drilling Using Autoencoders and Memory-Based Neural Networks

The drilling of carbon fiber-reinforced plastic (CFRP) materials is a key process in the aerospace industry, where ensuring high product quality is a critical issue. Low-quality of final products may be caused by the occurrence of drilling-induced defects such as delamination, which can be highly affected by the tool conditions. The abrasive carbon fibers generally produce very fast tool wear with negative effects on the hole quality. This suggests the need to develop a method able to accurately monitor the tool wear development during the drilling process in order to set up optimal tool management strategies. Nowadays, different types of sensors can be employed to acquire relevant signals associated with process variables which are useful to monitor tool wear during drilling. Moreover, the increasing computational capacity of modern computers allows the successful development of procedures based on Artificial Intelligence (AI) techniques for signal processing and decision making aimed at online tool condition monitoring. In this work, an advanced tool condition monitoring method based on the employment of autoencoders and gated recurrent unit (GRU) recurrent neural networks (RNN) is developed and implemented to estimate tool wear in the drilling of CFRP/CFRP stacks. This method exploits the automatic feature extraction capability of autoencoders to obtain relevant features from the sensor signals acquired by a multiple sensor system during the drilling process and the memory abilities of GRU to estimate tool wear based on the extracted sensor signal features. The results obtained with the proposed method are compared with other neural network approaches, such as traditional feedforward neural networks, and considerations are made on the influence that memory-based hyperparameters have on tool wear estimation performance.

Analysis of the Influents of Cutting Parameters in Drilling GFRP Composites Using Taguchi Method

Carbon Fiber Reinforced Plastic (CFRP) is widely employed today, mainly in industries, due to its required properties of high corrosion resistance, high strength, and lightweight, this work studies the influence of the cutting parameters on the surface roughness by drilling two types of carbon-fiber-reinforced polymer composite material (CFRP) Composites 0° angle and 90° angle, the investigated of the drilling of CFRP by using an experimental design based on the Taguchi L18 orthogonal array. Spindle speed, feed rate, and tool diameter were the input parameters, and surface roughness was the output. The cutting settings (410, 806, and 1003) rpm and two different HSS tools were employed in the drilling operation of the CFRP composite. The feed rates used were (0.1, 0.2, and 0.3) mm/rev (at 10 and 12 mm in diameter). The Taguchi approach, the cutting speed, feed rate, and tool diameter were optimized to be 1003 rpm spindle speed, 0.1 mm/rev feed rate, and 10 mm, respectively, at a 0° angle, the surface roughness was 2.74 µm, while at a 90° angle, 4.12 µm, surface roughness was created by the Taguchi optimization of the surface for the cutting variables. According to the ANOVA analysis of the surface roughness (Ra) for CFRP/0-angles, The P-value of the factor feed rate was 0.044 less than 0.05, while the p-values of the tool diameter and spindle speed were greater than 0.05. At the CFRP/90-angle, the p-values of the factors feed rate and spindle speed were both less than 0.05, while the p-value of the tool diameter was 0.208.

Bi-directional drilling of CFRPs: From principle to delamination suppression

Carbon Fiber Reinforced Plastics (CFRPs) are widely used in aerospace, automotive and other transportation industries because of their excellent material and mechanical properties. Nevertheless, up to now, drilling is still regarded as the most important process in the machining of CFRPs, and the delamination is one of the most challenging damage in drilling process. In this concern, we propose and implement a bi-directional drilling method for CFRPs hole-making. In this paper, the exit delamination formation mechanism was firstly analyzed to clarify the effect of bi-directional drilling on delamination suppression. The critical thrust force was calculated by considering both conventional and bi-directional drilling conditions. Based on the model, it can find that bi-directional drilling process itself can provide support without employing any extra facility. Finally, experimental validation indicates that the calculated critical thrust force showed a reasonable agreement with the experimental results based on conventional and bi-directional drilling. The hole exit delamination damage under the bi-directional drilling reaches the desired suppression effect with a reduction of 11.3%–27.9% compared to conventional drilling based on experiment results. Through an in-depth understanding of critical thrust force, the findings of this paper not only provide a new processing technology for drilling CFRPs, but also open a new avenue to improve the quality of drilling CFRPs by reducing delamination.

Prediction model of chisel edge thrust force and material damage mechanism for interlaminar-direction drilling of UD-CFRP composite laminates

Interlaminar-direction drilling of carbon fiber reinforced plastic (CFRP) is a new machining mode different from the conventional drilling. The thrust force on chisel edge of interlaminar-direction drilling is a key factor for the machining quality of CFRP. Therefore, it is necessary to accurately predict the thrust force on chisel edge, and reveal the material damage mechanism for the study of CFRP interlaminar-direction drilling. In this work, the chisel edge of the conventional twist drill is divided into two parts: the cutting edge and the rake face. By respectively establishing the thrust force models of the cutting edge and the rake face, the prediction model of the thrust force of chisel edge for interlaminar-direction drilling of unidirectional CFRP (UD-CFRP) is established. The reliability of the prediction model is verified by the designed experiments. Moreover, the response law of the thrust force of chisel edge to the machining parameters is discussed in detail, and the material damage mechanisms under the action of chisel edge and main cutting edge are revealed by micro characterization of materials. This study is expected to enrich the theory of interlaminar-direction drilling of CFRP, and provide a theoretical basis for guiding the strategy about interlaminar-direction drilling of CFRP.

Experimental investigation on machining performance during orbital drilling of CFRP

As the most promising carbon fiber reinforced plastic (CFRP) hole making method, orbital drilling is widely concerned. This paper aims to understand the influence of the cutting parameters, tool diameters and ratio between milling and drilling (\({R}_{m\&d}\)) on machinability in CFRP orbital drilling. The effects of cutting parameters on thrust force and cutting temperature were studied by orthogonal experiments, and experiments were performed to investigate the variations of tool diameters, ratio between drilling and milling on thrust force, cutting temperature, tool wear and machining quality. The experimental results show that the spindle speed and axial feed rate have apparent effects on thrust force, and the tangential feed rate appreciably impacts on the cutting temperature. The selection of tool diameter and the \({R}_{m\&d}\) has specific influence on tool wear, machining quality and cutting temperature. The result is helpful for selecting cutting parameters and tool diameters for high quality hole machining in CFRP orbital drilling.

Modeling Evolution of Cutting Force in Ultrasonically Assisted Drilling of Carbon Fiber Reinforced Plastics.

In this study, the effects of process parameters (feed rate, spindle speed, and ultrasonic power level) on the cutting force and delamination in the ultrasonic vibration-assisted drilling of carbon fiber-reinforced plastics (CFRPs) have been investigated. A series of drilling tests under various conditions defined by the design of experiment technique were conducted. The evolution of the cutting force during drilling cycles was measured and analyzed. Experimental analysis results based on the Taguchi method and analysis of variance show that the spindle speed is an influential factor affecting the cutting force with a contribution of 75.36%, and the feed rate significantly affects the delamination damage with a contribution of 46.57%. In addition, the cutting force was found to increase with drilling cycles at different rates, which depends on the process parameters used in drilling. The evolution behavior of cutting force was well fitted based on the process parameters by proposed regression models. Experimental validation indicates that the predicted forces show reasonable agreement with measured values under different conditions and reveal good prediction performances, with a root mean square error of 5.6 and a mean absolute percentage error of 5.8%. In drilling tests with variable cutting conditions, the evolution of the cutting forces predicted based on the selected parameters was successfully verified when compared with the measured results, with RMSE and MAPE values of 7.55 and 5.61%, respectively. As a conclusion, this predictive model provides an effective basis for selecting appropriate drilling parameters to suppress the cutting force on CFRP composites.

Study on exit damage characteristics of ultrasonic vibration assisted drilling of CFRP

In order to solve the disadvantage of tearing and burr damage in axial drilling of carbon fiber reinforced plastics (CFRP), the stiffness at the exit is increased by applying different drilling speed in ultrasonic vibration assisted drilling (UVAD) Firstly, compared with conventional drilling (CD), ultrasonic assisted vibration drilling can realize the separation of axial tool and tool/chip; Secondly, the cutting speed characteristics of ultrasonic assisted drilling at different speeds are analyzed, and the change of cutting speed characteristics of ultrasonic assisted drilling at low speed is obvious; Finally, the change trend of contact rate at different speeds is analyzed. The experimental results show that the stiffness of ultrasonic assisted vibration drilling is significant. Taking the speed of n = 100 r/min as an example, the stiffness of ultrasonic assisted drilling is about twice as high as that of rotary speed n = 2400 r/min, which is about 8% higher than that of ordinary drilling when n = 100 r/min; Hole exit quality of low-speed drilling: compared with CD, the tearing factor of ultrasonic assisted vibration drilling is lower. Therefore, this method provides a way to improve the hole quality of CFRP.

Effect of workpiece preheating on tool wear and delamination at the hole exit in high feed drilling of carbon fiber reinforced plastics with diamond-coated tools

High feed drilling of carbon fiber reinforced plastics (CFRP) poses a risk of serious tool wear and delamination caused by high drilling thrust force despite improving productivity. However, by taking advantage of the proper thermal softening of the epoxy matrix in CFRP, a decrease in forces related to tool wear and delamination is achievable under high feed. Through this study, thermal softening of epoxy matrix by preheating was effective in reducing thrust force and tool wear in the drilling of CFRP with diamond-coated tools. Hole exit delamination factors decreased by adjusting workpiece temperature to the proper value using a developed preheating system under high feed (0.2 mm/rev).

Control of Fine Cutting Chips to Improve the Processing Environment in CFRP Drilling

Carbon fiber reinforced plastic (CFRP) is increasingly used in aerospace, automobile, and other industries. With the improvement of carbon fiber reinforced thermoplastic molding technology using thermoplastic resin, it is expected that the applications of CFRP will be expand further. Because of the following issues, CFRP is known as a difficult-to-cut material. i) Machining CFRP is difficult. ii) Its finished surface deteriorates due to delamination and uncut fiber. iii) It has a shortened tool life due to severe tool wear. In addition to these issues, we has been problem presentation of fine cutting chips generated by machining. Because these fine cutting chips may scatter in the atmosphere and adversely affect the human body and machine tools, we have established a chip disposal technology that suppresses these issues to improve the processing environment. A previous study reported that shape of the tool edge is responsible in suppressing the generation of fine cutting chips. Here, we experimentally investigated the effects of tool edge shapes on the chip collection rate and tool life. An attempt was made to determine whether the same effect can be obtained by using the outside dust-collection method which is known that the dust collection efficiency is low. We revealed that the chip collection rate increases if a tool that suppresses the generation of fine cutting chips is used instead of a conventional tool; furthermore, the tool life is insensitive to coating. In contrast, a comparison of our results with previous findings indicates that the tool with a sharpened cutting edge has a longer tool life than the conventional twist drill with honing. A high cutting chip collection rate was obtained, even with the outside dust-collection method, which led to an improvement in the working environment.

Effects of heat accumulation on the characteristics of hole wall temperature and damages in drilling of UD CFRP

Application of carbon fiber reinforced plastic (CFRP) in aircraft load-carrying structure makes the component become thicker and damage tolerance get stricter. The heat accumulation highly increases the hole wall temperature along feeding direction during thicker CFRP component drilling due to the low thermal conductivity, which highly deteriorates the hole quality. Therefore, this paper proposed a hole wall temperature measurement experiment at various fiber cutting angles with different measuring distances to investigate the effects of heat accumulation on the cutting temperature and damages. Results show hole wall temperature in the vicinity of hole-exit increases by almost 20⁓40 °C and 30⁓65 °C separately for S=3000 rpm and S=5000 rpm. The fiber shearing and bending when against fiber cutting seriously increases temperature near the hole wall by increasing the fiber-rich regions and contact time between workpiece and cutting lip. Moreover, the maximum temperature distribution maps along feeding direction and radial direction were separately drawn for the first time to analyze the heat accumulation and overheating areas. The hole wall along the hole edge and feeding direction were detected, and severe matrix cracking, fiber bending, and fiber-matrix debonding occurred at the position where maximum temperature was located. In the future, the findings of borehole temperature characteristics can be used to refine the existing temperature model of CFRP drilling.

High-frequency vibration effects on the hole integrity in rotary ultrasonic drilling of carbon fiber-reinforced plastic composites

This investigation represented a fundamental research on the potential effects of the high-frequency vibration on the hole integrity involved in rotary ultrasonic drilling (RUD) of carbon fiber-reinforced plastic (CFRP) composites. It was found the increased thickness of the CFRP plate shrunk the flowing velocity of the coolant, which brought about the residual chippings gradually accumulated at the radial clearance between the tool and the material. Furthermore, the chipping accumulation at the clearance seriously increased the friction effects and the resultant thermal load, thus leading to the chipping adhesions on the tool surface and machined cylinder jamming at the central hole of the tool. The mutual constrain between two vertical bundles brought the delamination around the holes generated in conventional drilling (CD) process to a termination at the bundle interface. The ultrasonic superimposition reduced the thrust force of the diamond tool which provided inadequate energy for the delaminated fibers reaching the bundle interface. Moreover, hole position on the two-dimensional orthogonal fabrics significantly influenced the propagation of the delaminated fibers, which weakened the effects of the drilling parameters on the delamination dimensions. Additionally, superimposing an ultrasonic vibration prolonged the abrasive trajectories and increased their overlapping probability, and the induced smoothing effects resulted in the obvious reduction of the surface roughness. The tensile stress exerted on the margin of the machined surface was responsible for the initiation of the CD delamination. After the delaminated fibers reached the bundle interface, the further extrusion of tool brought about the margin suffered from the shear stress, thus leading to the collapse of the machined cylinder. Considering the thrust force of the diamond tool and the undrilled thickness of the machined surface, the critical conditions of the delamination initiation were developed, which revealing that the decreasing of the thrust force caused the reduction of the critical undrilled thickness.

Deformation Resistance Performance of Carbon Fiber-Reinforced Plastic Machined by Controlling Drilling Area Temperature below the Glass Transition Temperature.

Drilling of carbon fiber-reinforced plastics (CFRPs) is a challenging task in aviation and aerospace field. Damages, which can reduce the strength of the structure, often occur during secondary machining operations due to the applied cutting force and generated heat. The main objective of this study was to investigate the drilling performance and the deformation resistance of CFRPs subjected to cryogenic treatment based on glass transition temperature (Tg). Therefore, a cryogenic machining approach was adopted by fixing the workpiece inside a cryogenic box to drill CFRPs. The machining performance was briefly evaluated. Moreover, a through-hole drilling method was promoted to analyze the mechanism of different deformation mechanical properties. The results showed that the cryogenic machining approach improved the machining performance of CFRPs. Nevertheless, the residual intensity of cryo-treated specimen decreased (about 7.14%) due to the Tg-based viscoelasticity. These results demonstrate the great potential of this approach in advanced industrial applications and further pave the way for efficient secondary machining operation of CFRP components.

A novel method for predicting delamination of carbon fiber reinforced plastic (CFRP) based on multi-sensor data

Carbon fiber reinforced plastic (CFRP) has been widely used in many fields such as in the aerospace and automotive industries. Drilling of CFRP is a key process in the manufacture of CFRP components. The existing quality control and tool change decision methods are mainly based on delamination damage. However, estimating delamination damage in situ is still a challenge in the process of continuous drilling. To solve this problem, a comprehensive delamination prediction method based on multi-sensor data is proposed in this paper. In process of the drilling, the force, torque, temperature, vibration and hole exit images were collected, and the delamination was quantified by a proposed statistical delamination factor Fs. Singular spectrum analysis (SSA) is used to smooth the Fs sequence to reduce randomness. Then, a XGBoost-ARIMA model is constructed for rolling prediction of Fs. Finally, drilling experiments were carried out to verify the effectiveness of the proposed method. The experimental results showed that compared with traditional delamination evaluation factors, Fs reduced the mean square error (MSE) of prediction by more than 50%. Compared with that of traditional machine learning models such as an SVM and ANN, the MSE of the model’s regression part is decreased by more than 39%. The proposed method can provide a solution for real-time and in situ prediction of delamination damage in the continuous drilling process of CFRP components.

Investigation on a novel variant-dimension vibration-assisted drilling system for CFRP: locus model, control strategy, and machining experiments

Ultrasonic vibration-assisted drilling, which can obtain the minimization of geometrical defects, provides a solution for the drilling of carbon fiber-reinforced plastic (CFRP) by adding a displacement of a micro-scale amplitude with a frequency to the tool tip. However, single vibration mode in drilling of CFRP cannot satisfy the different requirements of various drilling stages in CFRP and limits the applications of current ultrasonic vibration-assisted drilling of CFRP. To overcome the limitation and improve the performance of vibration-assisted drilling process in CFRP components, a novel variant-dimension vibration-assisted drilling system (VD-VADS) is proposed. The VD-VADS is specially designed to be capable of delivering variant-dimension vibrations at the tool tip for drilling holes in CFRP by producing one-dimension longitude vibration, two-dimension elliptic vibration, and three-dimension composite vibration, which can be transferred to adapt to various drilling stages in CFRP. An analytical model of the VD-VADS’s locus will be formulated to facilitate the prediction of the loci of the tooltip and design and realization of the prototype device. The control strategy of variant-dimension vibration mode of the proposed VD-VADS is established and realized for various drilling stages in CFRP. To validate the machining performance of the VD-VADS, five groups of drilling experiments under the conventional drilling and various vibration-assisted drilling processes were performed. The performance tests and comparison results of the obtained holes between the conventional drilling and various vibration-assisted drilling processes indicate that the proposed VD-VADS is capable of generating holes with better overall quality than the current single vibration-assisted drilling processes.

Influence of hole quality on fatigue life of drilled CFRP with the different ply orientation angle

In this study, the effect of drilling quality on fatigue life of UD, 0/90, and ± 45 fiber angle carbon fiber reinforced plastics (CFRP) was investigated. CFRPs were drilled using WC, HSS, and Brad Spur tool types that have different geometries and materials at different feed rates of 0.05, 0.10, and 0.15 mm/rev, and at the different spindle speeds of 1000, 3000 and 5000 rev/min. Thrust forces were measured during the drilling of CFRPs, and surface roughnesses, deformation factors, and maximum tensile forces were measured after drilling operations. Thrust force, surface roughness, and deformation factor were evaluated in terms of drilling quality. The drilling parameters that cause the best, average, and worst drilling quality were determined. Then, fatigue behaviors of CFRPs drilled in these drilling parameters were investigated. Fatigue tests were carried out at %75, %80, %85, and %90 load ratios based on the lowest tensile force of the drilled samples. As a result of the study, it was determined that the thrust force, the deformation factor, and the surface roughness increased as the feed rate increased. However, the thrust force, the deformation factor, and the surface roughness decreased as the spindle speed increased. Besides, the best drilling quality was obtained from the drilling operation performed using WC tool type, at a spindle speed of 5000 rev/min and a feed rate of 0.05 mm/rev. The worst drilling quality was obtained from the drilling operation performed using Brad Spur tool type, at a spindle speed of 1000 rev/min and a feed rate of 0.15 mm/rev. With the decreasing drilling quality, a significant decrease occurred in the tensile force and fatigue life of CFRPs. The tensile load and fatigue life of CFRPs drilled in optimum drilling parameters were obtained higher. In the case of selecting the correct drilling parameters, it was observed that the reduction in fatigue life of CFRPs could be prevented ratios of %22–49.

Drilling process improvement by Taguchi method

This paper focuses on the optimization of drilling input variables using the Taguchi method to reduced drilling defect-delamination on carbon fiber reinforced plastic (CFRP). CNC vertical machine used to conduct experimental work. The experimental work was performed on CFRP material using twist drill with different helix angle under dry cutting conditions. The spindle speed, feed rate and helix angle were considered as input variables for reduced delamination- defect. The optimum spindle speed 800 rpm, feed rate 0.2 mm/rev and helix angle 35 gave minimum delamination defect 1.1311. Analysis of variance (ANOVA) show feed rate is most influencing variable in CFRP drilling process. The Confirmation results show that Taguchi method was notably successful in the optimization of drilling parameters for reduce delamination (drilling defect).