The solid-state friction stirring processes are often recommended for the joining of thermoplastic polymers. This work addresses different tool pin profiles on lap-weld characteristics for semi-crystalline nylon-6 in friction stir welding. The objective was to achieve uniform weld profile over the weld line for improved joint strength and ductility. Various sensor signals like tool thrust, stirring torque, thermal cycles and input electrical power were acquired during welding. The longitudinal weld profile was monitored using time-domain integrated thrust-torque-power signatures, while joint mechanical behaviour was assessed through peak temperature and cooling rate. The hidden time-frequency information in power signal was processed through wavelet packet analysis to characterize process stability. The higher swept-ratio square pin provided the highest strength efficiency (>= 68%) with smoother torque-power at high tool speed (2400 rpm) while cylindrical pin improved joint ductility despite fluctuated stirring torque. Minimal deviation in peak temperature in advancing to retreating side indicated uniform heat balance with square and cylindrical pin. Power loss was significantly reduced (<= 7%) at higher rotational speeds using square pin. The low frequency band (1-125 Hz) power wavelet was predominant in dictating process stability. The results confirm that wavelet analysis of power is highly effective for weld quality monitoring.

This study investigates the small-hole drilling behaviour of additively manufactured hybrid Kevlar fiber reinforced polymer (KFRP) laminates, addressing the critical challenge of drilling-induced damage in advanced composite structures, and introduces an integrated experimental-MCDM framework for robust optimization of drilling parameters. KFRPs are gaining importance in aerospace and automotive sectors due to their exceptional toughness, impact resistance, and low weight. However, drilling these composites remains challenging because of excessive thrust, torque variation, fiber pullout, and delamination, which compromise hole integrity. The experiments were conducted on 3D-printed laminates fabricated using Fused deposition modelling (FDM), considering drill diameter (1.0-1.6 mm), spindle speed (2000-3000 rpm), and feed rate (0.01-0.03 mm/rev). Results revealed that thrust force increased notably with drill diameter (17.02-49.96 N), while torque peaked at 1.3 mm due to complex fiber-tool interactions. Delamination emerged as the predominant damage, intensifying with higher feed rates. To achieve optimal drilling conditions, Multi-Criteria Decision-Making (MCDM) techniques TOPSIS, COCOSO, and MOORA were employed. All methods converged on the 1.3 mm drill, 3000 rpm spindle speed, and 0.01 mm/rev feed rate as the optimal parameters, minimizing thrust (13.303 N), torque (0.09 Nm), and delamination (Fd = 1.154). Sensitivity analysis validated the robustness of these results, highlighting delamination weighted scenarios favouring the 1.6 mm drill. The study uniquely integrates experimental analysis with MCDM optimization, establishing a systematic framework for precision drilling of additively manufactured KFRPs. The proposed framework provides a practical decision-support tool for selecting drilling parameters in hybrid composite machining, with direct relevance to precision manufacturing applications.

The present work addresses the feasibility of friction stir spot welding (FSSW) of metallic aluminum alloy (Al6061) to thermoplastic polycarbonate (PC) sheets using a tapered pin tool incorporating real-time process monitoring with thrust-torque signals. Sensitivity analysis identified axial tool thrust during dwelling as the most superior indicator for joint integrity (>= 40.1%) due to its role in enhancing interfacial mixing and bonding. The tool revolving speed primarily governs the process stability (>= 30.9%) and thus predominantly enhances the weld strength (36.5 MPa) through controlled materials stirring. In contrast, dwell time governs the joint ductility (35.5%) by promoting adequate consolidation, while plunge depth dictates the weld hardness (43%) through prolonged deformation along dissimilar interface. An integrated multi-criteria decision-making (MCDM) analysis using ARAS, TOPSIS, and GRA provided consistent optimization trends with a strong rank correlation coefficient (> 0.9), confirming methodological reliability. The findings establish a quantitative framework for optimizing FSSW of dissimilar Al-PC, offering a validated approach for achieving improved mechanical behaviour through balanced process stability.

The airplane structure is often made up using carbon fiber reinforced plastic (CFRP) stacking with a metallic sheet to improve excessive load carrying and shock-absorbing capability with reduced fuel economy. It is a challenging task to drill dissimilar CFRP-Al metallic stack because the hot continuous metallic chip mutilates the hole surface in addition to drilling-induced delamination. The present work addresses the parametric effect on delamination, roughness, and circularity error of the drilled hole along with chip morphology using different drill geometry on the fabricated CFRP [0 degrees/-45 degrees/90 degrees/45 degrees](2s) stack over an aluminum 7075 sheet. A drill tool dynamometer was used to capture axial thrust with associated torque variations during drilling which were further used in process monitoring. The most critical unlike interface drilling has been scrutinized using instantaneous force-torque slopes along with scanning electron micrographs. The machining time loss during CFRP -> Al interface drilling has also been processed. Finally, a comparative assessment has been made on the predictability of hole quality features among various sensor-based strategies using response surface methodology. The drilled-hole surface quality was significantly improved at high spindle speed (2250 rpm), and low feed rate (0.025 mm/rev) using a low drill point angle (110 degrees). The thrust force was found to be a prime indicator of drilled hole integrity than torque whereas peak torque and its slope in the initial stages of the drilling cycle strongly correlated with surface delamination. The top surface delamination was somewhat severe (>= 1.6) at high drill thrust (>= 40 N) with high torque (>= 0.45 Nm).

Carbon fiber-reinforced plastics (CFRP) have excelled in mechanical performance, replacing metals in structural design. However, their challenging machinability especially in drilling for assembly necessitates careful optimization of process parameters for mass production efficiency and waste reduction. This study explores the optimization of the drilling process for carbon fiber-reinforced composite laminates with a stacking sequence of [0/–45/90/45]2s. Using the tungsten carbide twist drills, experiments were conducted on quasi-isotropic CFRP laminates with a thickness of 10 mm. The drilling process parameters, including spindle speed and feed rate, were systematically varied to investigate their influence on drilled hole defects. A three-axis CNC milling center equipped with a piezoelectric dynamometer captured thrust force and drilling torque signals, forming the basis of the experimental methodology. The research employs multi-criteria decision-making techniques, such as MOORA, TOPSIS, and VIKOR, to identify the optimal combination of parameters for minimizing defects and enhancing drilling efficiency. In this study, the synergy of these multi-criteria decision-making techniques establishes a novel framework, demonstrating their efficacy in addressing the challenges associated with CFRP laminate drilling. Quantitatively, the optimized drilling parameters, combination of high speed, low feed rate, and low point angle tool resulted in a remarkable 20

The drilling of carbon fiber reinforced plastics (CFRP) composite laminates is quite different from those of traditional metal owing to the anisotropic nature of the composite laminates. The high stiff fibers were alternatively placed with a malleable matrix making things worse when the drill tool encounters these materials having different mechanical and thermal properties. Although having exceptional properties like a high strength-to-weight ratio, high stiffness ratio, corrosion resistance, etc., it has been kept in the hard-to-machine material category. Therefore, while drilling these materials an optimized parameter setting is essential for ensuring high standard damage-free holes for structural building purposes. A Multi-criteria decision-making (MCDM) method has been used to deal with the difficulty faced while selecting the process parameter settings from a large number of potentially viable alternatives. Therefore, in this particular research paper, a decision-making model using the Additive ratio assessment (ARAS) method was used for finding the best possible alternative for drilling CFRP laminates. It was confirmed that this method can be utilized in solving the real-time problem of selecting the best parameter setting while drilling CFRP composite materials. Based on this method alternative with a low drill point angle (110°), high spindle speed (3200 rpm), and low feed rate (0.025 mm/rev) was found to be the best setting for drilling holes.

Carbon fiber-reinforced polymers are one of the lightweight materials used in structural design due to their exceptional mechanical performances. The drilling operation is indispensable as it facilitates the assembling of various manufactured components. However, drilling of fibrous laminates is deemed difficult in comparison to the traditional metals because of the anisotropic and non-homogeneous nature. The present work addresses the parametric effect on the drilled hole delamination and further reduces it with an optimal combination of parameters for multi-objectives using different multi-criterion decision-making techniques. Initially, the response surface-based regression model of delamination as a function of three static inputs has been developed, further revised with induced thrust as well as mean torque for the improvisation of the prediction capability. Finally, for the overall improvement, a decision-making model has been used that includes grey relation analysis, technique for order performance by similarity to ideal solution, and VIsekriterijumsko Kompromisno Rangiranje method. The delamination was found to be minimum at a low drill point angle (100 degrees), high spindle rotation (2150 min(-1) ), and low feed rate (0.025 mm/rev) due to reduced thrust force. The mean absolute prediction error was significantly improved considering root mean square torque rather than axial thrust with process variables.

Carbon fiber reinforced plastic laminates have been kept under the category of hard-to-machine materials despite having some unmatchable properties like high strength, stiffness, corrosion resistance, etc. The heterogeneous nature of the material makes the essential secondary machining process a challenging task to perform. Drilling is always considered the effective way to drill holes necessary for the assembling purpose in structure building. Though, drilling the CFRP laminates critically affected by the abrasiveness of the reinforcing fibers eventually produces various defects. In this particular experimental analysis, a decision-making model associated with the Multi-objective optimization of ratio analysis (MOORA) method has been used in selecting the best possible parameter setting for minimizing defects. The results suggested that this method is found to be effective in solving the real-world problem of selecting the optimized parameter setting in drilling CFRPs. The best possible combination of low point angle, high speed, and low feed rate produces the least drilled hole defects.

The use of carbon fiber-reinforced plastics (CFRP) in aerospace and automobile industries gains momentum in the last two decades, which indicates the necessity of machining these materials for large-scale production. However, the tool is prone to relatively more wear during the drilling of heterogeneous material like CFRP, unlike metal machining. This study investigates the tool wear progression with an increase in the number of drilled holes using three different tools, namely uncoated, TiAlN-, and TiN-coated carbide drills keeping the drilling parameters and tool geometry constant for woven CFRP composites. The effect of drill wear on the hole quality features like delamination damage, roughness, and circularity error was investigated. Thereafter, the time–frequency wavelet analysis of the thrust force with associated torque signals has also been examined by decomposing them up to the third level to completely characterize the process. The flank wear was increased with an increase in the number of holes irrespective of tools types though the TiN-coated tool was found to be advisable to use in industrial practices. The worn-out tool produces moderately enhanced thrust directly responsible for severe delamination damage. The wear-out tool changes the material removal mechanism from cutting to tearing which leads to a rise in temperature causing thermal degradation of the matrix that in turn amplified the roughness and circularity error. The low-frequency band force wavelet was a better indicator of tool wear, whereas the low-frequency band torque wavelet was found to be better for the prediction of hole quality features.

In the modern world, lightweight fibrous composites materials with high mechanical properties are the first choice for structural design purpose. Excellent mechanical properties and easy to make and shape quality make it the prime substance for aeronautics as well as automobile manufacturing units. However, drilling of these non-homogenous fibrous polymers is quite tricky in compare to the other traditional metal. In this paper, eighteen different sets of the parametric combination were derived, using Taguchi’s L18 orthogonal array. Grey relational analysis (GRA) has been used to find the optimal drilling parameter setting by optimizing the three performance characteristics, like thrust force, torque, and delamination factor. The axial thrust force was found to be the most influential feature in predicting delamination factor. However, the thrust force was maximum at high feed and low spindle speed and higher tool point angle. Analysis of variance is also used for predicting the most contributing parameter and it was found out that, feed rate has the maximum impact in drilling carbon fiber reinforced plastics (CFRP).

Drilling of fibrous composites like carbon fiber reinforced plastics (CFRPs) is always considered a grim job to perform owing to its abrasiveness and inhomogeneous properties. Compared to the available studies, the present work addresses the parametric investigation on drilling capability of TiAlN- and TiN-coated drills over the uncoated one. The delamination factor, surface roughness, and circularity error in CFRP were considered as the quality features. The acquired thrust and torque were analyzed in the time domain as well as the time–frequency wavelet field, followed by a sensitivity analysis between decomposed original force–torque signals in different phases. Finally, an attempt was made to improve the predictability of drilled hole quality using decomposed wavelets of force and torque extended to hybrid force–torque wavelets of the best features to the developed regression models. The feed rate was more predominant than spindle speed on delamination evidenced by higher axial thrust particularly using coated tools. However, the coated drills generated more uniform torque than the uncoated drills and improved the drilled hole quality as well. The torque wavelet was a better indicator of hole surface integrity than force wavelets in which intermediate frequency band torque and low-/high-frequency band force wavelets were found to be more significant.

Carbon fiber reinforced polymers (CFRPs) laminates are one of the lightweight materials that have been around for a while in the manufacturing sector for its superior properties. However, the aviation industries are considered as the prime shopper of these fibrous composites in building structural parts of airplanes. Despite having some delectable properties like high strength, high fatigue resistant, high stiffness, high resistant to a corrosive environment, etc. it has been kept in the difficult-to-cut category. The machining of the CFRPs is quite tricky due to the anisotropic, heterogeneous, and abrasive nature. Drilling is considered as the final machining operation in the assembly line in most of the cases as holes are the absolute need in assembling purpose. However, the wedge-shaped drill, while cutting high strength fibers, produces various types of damages like delamination, surface roughness, fiber pullout, matrix breakage, etc. Among these, delamination is considered as the most vital and can influence the joint quality for which it needs a more significant concern. In this particular experiment, the drilling experiments have been designed by using Taguchi’s L18 orthogonal array. The drilled persuaded damage like delamination factor and two sensory output parameters such as thrust force and torque has been acquired using data acquisition system and further analyzed and effort has been made to relate with the hole quality. Finally, a multi-objective optimization of the responses was made by utilizing the response surface methodology (RSM) approach. The delamination damages found to be less with a parameteric setting in case of lower feed rate (0.025 mm/rev), small point angle tool (108°), and at a higher spindle speed (3125 rpm).

Carbon fiber reinforced plastics (CFRP) along with metallic stacks highly used in avionics and other industries. However, assembling of such ancillaries needs holes for which primarily drilling is necessary. Drilling of such dissimilar material combinations having different mechanical properties results numerous defects. The reduction of such defects with acceptable hole quality needs a study on the effect of variations of the cutting parameters. This paper presents an experimental study on the interaction effect of different cutting parameters, like spindle speed and feed rate on delamination, circularity, and surface roughness, which was considered as hole quality characteristics. Aluminum alloy (7075) was used as the stacking metal with fabricated CFRP at fiber orientation of 0 degrees/90 degrees and 45 degrees/-45 degrees. Drilling is carried out using Tungsten-Carbide Twist Drill of point angle 1100 degrees, 1180 degrees, and 1250 degrees. Drilling defects were found to be minimum for the least point angle, higher spindle speed, and lower feed rate.

Fiber-reinforced plastic is one of the top priorities lightweight materials with excellent mechanical properties for the aerospace industries in recent years. However, it is difficult to machine despite having unique properties due to its non-homogeneous and abrasive nature in alternate fiber and matrix layers. Thus, it is found to be a challenging task to drill hole on such hard-to-machine materials, which is highly essential for the development of most of the engineering structural components. The present work addresses various drilling-induced defects such as delamination, circularity error, and roughness variations in the hole surface during drilling of quasi-isotropic cross-fiber oriented bi-directional woven-type carbon fiber reinforced plastic laminate using a full factorial design of experiments for different drill geometry. The response surface methodology was considered for the regression model development, which was found to be highly significant. The machining forces with associated torque have also been acquired during drilling, which was divided and further analyzed in time domain to correlate with drilling flaws. The drilling-induced delamination was found to be higher at a high feed rate using a higher drill point angle due to substantial thrust force generation at the initial stages in the drilling cycle. However, the internal surface finish with associated circularity error was reduced for higher spindle speed with less feed rate using a low drill point angle because of low torque fluctuation at the final drilling phases. The axial thrust force was found to be a prime indicator of drilled hole surface delamination, whereas drilling torque precisely indicated internal surface roughness as well as circularity error. The global root mean square, along with a local peak of thrust and torque, both were highly essential to completely characterize the drilled hole quality.

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 is evaluated by considering cutting speed (600, 800, 1000 and 1200 rpm), feed rate (0.05, 0.1, 0.2 and 0.25 mm/rev) and point angle (110°,118° and 125°) as affecting process parameters. In this work experiments are conducted to analyze the delamination using image processing technique, circularity using CMM and surface roughness using surface roughness tester. Experimental results showed that the thrust force and torque, hole roundness decreases with increase in cutting speed and increases with increase in feed rate. The delamination factor decreases with increase in both spindle speed and feed rate. It has been observed that the WC tool with point angle 110° showed the best result compared to all other tools for drilling CFRP composite. It can be concluded that at high cutting speed, low feed rate and small drill point angle is best for drilling of CFRP composites.