Drilling Of CFRP Research Articles

Machining-induced damages in the drilling of CFRP under dry and cryogenic environments

Machining-induced damages in the drilling of CFRP under dry and cryogenic environments

Experimental study on step drill geometry and pecking drilling with variable parameters processing method as drilling of CFRP and Ti stacks

Integrated drilling of CFRP and Ti stacks is a challenging task due to the disparate machining property. Choosing proper tool structure and processing method are effective ways to obtain high-quality holes. In this paper, drilling experiments are carried out to research the performance of step drills and variable processing method in drilling of CFRP/Ti stacks. The effect of ratio of primary cutting edge diameter, point angle of primary cutting edge and secondary cutting edge and the location of variable processing on the burr of Ti layer, delamination and thermal damage are analyzed. Decrease the primary cutting edge can restrain the thermal damage and delamination. The point angle of secondary cutting edge has the influence on the final holes directly, and as drilling from Ti to CFRP, the point angle of secondary cutting edge is 110°, by contrast, as drilling from CFRP to Ti, the point angle of secondary cutting edge is 130°. Pecking drilling with variable parameter can reduce the drilling damage. As the pecking drilling feed rate increase from 2f to continuously drilling, thermal damage increases by 176.4 %. Variable parameter processing method can reduce the thermal damage as drilling of Ti layer with low spindle speed.

Influence of Machining Condition and Nano-Graphene Incorporation on Drilling Load and Hole Quality in Both Conventional Drilling and Ultrasonic-Assisted Drilling of CFRP

Influence of Machining Condition and Nano-Graphene Incorporation on Drilling Load and Hole Quality in Both Conventional Drilling and Ultrasonic-Assisted Drilling of CFRP

A study on the ultrasonic vibration on the cutting performance during ultrasonic-assisted drilling of CFRP with twist and dagger drill bits

During the drilling process of carbon fiber reinforced polymer (CFRP), defects such as exit delamination, tearing, and burrs are prone to occur, among which excessive axial force during drilling is the main reason for the generation of exit delamination defects. In this study, ultrasonic-assisted and conventional drilling with twist and dagger drills were investigated on 5 mm-thick multi-directional laminated fiber sheets made of T300-12k/AG80 carbon fiber composite with different orientations. The axial force evolutions in each case were monitored when drilling holes in CFRP plates, and the axial force of drilling and the appearance characteristics of hole outlet were compared. The experimental results showed that the ultrasonic assisted drilling reduced the axial drilling forces of twist and dagger drill by up to 20.6% and 30.7%, respectively, compared to conventional drills. In addition, as the feed rate increases, the axial force of drilling gradually increases, and the exit delamination factor shows an overall increasing trend. The ultrasonic vibrations reduced the exit delamination damage of both drills. A special structure of the dagger drill effectively avoided exit delamination during ultrasonic-assisted drilling, which makes the incision more neat to improve the processing quality.

Formation mechanism of outlet damage in interlaminar drilling of CFRP

Formation mechanism of outlet damage in interlaminar drilling of CFRP

Mechanical drilling force model for longitudinal ultrasonic vibration-assisted drilling of unidirectional CFRP

Mechanical drilling force model for longitudinal ultrasonic vibration-assisted drilling of unidirectional CFRP

Investigation of CFRP damages induced by the interface high temperature and mixed tool wear mechanism in drilling of thin-walled CFRP /Ti stacks

Due to the poor thermal conductivity and machinability of CFRP and Ti6Al4V, significant heat accumulation at the interface and rapid tool wear are considered the main factors restricting the hole quality. This study conducted a thin-walled CFRP/Ti stack drilling experiment to investigate the evolution of the thrust force, temperature and tool wear versus different drilled hole numbers and spindle speeds, affected by which the novel material removal behavior was revealed. Results showed that the thrust force and interface temperature increased with the hole number and spindle speed, causing a significant increase in the cutting edge rounding and flank face wear dominated by the many fiber bundles and metal debris. In turn, the various tool wear led radial interface temperature to alternately transfer between Φ = 45° and 135°. Under the cyclic thermo-mechanical function, the fibers underwent significant bending deformation as they lost the support of the degenerated matrix resin, forming severe subsurface damage when the interface temperature exceeded the matrix glass transition temperature (Tg = 110 °C). Combined with the comprehensive evaluation of exit damages, a relatively higher spindle speed was preferred for selecting the initial drilling of thin-walled CFRP/Ti stack and gradually reducing the spindle speed with increasing tool wear extent.

Experimental Investigation of drill tool types on delamination error in drilling of CFRP

Experimental Investigation of drill tool types on delamination error in drilling of CFRP

Experimental analysis of entrance and exit damage mechanism affected by the structural dynamic deformation characteristics during drilling of thin-walled CFRP

Due to lack of effective backup when drilling aircraft thin-walled CFRP structure, serious dynamic structural deformation including vertical and in-plane deformation usually occur, which extremely changes the cutting behavior and materials removed mechanism, causing severe entrance and exit damages. Therefore, this paper proposed a dynamic deformation measurement experiment in vertical and horizontal direction at various processing parameters to analyze their effects on cutting mechanism and damages distribution. Results show the vertical and in-plane deformation occurrence are highly dependent on the actual positions of tool-CFRP system. Namely elastic deformation, local deformation and drawback reflection appear many a time in different stages, causing obvious sudden change of thrust force and different initiation and propagation characteristics of damages. With the feed rate increasing and workpiece thickness decreasing, the maximum displacements of every stages all increase and some thinner workpiece displacement exceed several times the plate thickness. The larger in-plane deformation will nonuniformly distribute along borehole exit due to the different cutting mechanism and strength of different fiber cutting angles. The larger elastic deformation and drawback action in vertical direction will change the out-ply material remove mechanism into mainly puncture rather than only cutting. Under the joint action of deformation in two directions, the loose surface damages composed of delamination and uncut fiber will gather heavily at exit.

Mechanical model of thrust force and torque in longitudinal-torsional coupled ultrasonic-assisted drilling of CFRP

Mechanical model of thrust force and torque in longitudinal-torsional coupled ultrasonic-assisted drilling of CFRP

Tool breakage monitoring based on sequential hypothesis test in ultrasonic vibration-assisted drilling of CFRP

Tool breakage monitoring based on sequential hypothesis test in ultrasonic vibration-assisted drilling of CFRP

Novel tool for damage reduction in orbital drilling of CFRP composites

Owing to the requirement of structural connection in the aviation industry, the drilling of CFRP becomes the most common machining process. Damages caused by drilling often occur, which affects the load-bearing capacity, as well as the reliability of the components. Consequently, the enhancement of the CFRP components processing quality is of great significance. In this paper the advantages of orbital drilling and step drill are analyzed, and an orbital drilling and reaming tool (ODR) combining the advantages of two method is proposed, which can effectively reduce the damage of hole making in CFRP. The machining process with ODR tool is analyzed both theoretically and geometrically. An upward push-cut effect is found at the exit, the fibbers at the edge of exit can be cut off in upward direction completely, and the defect can be suppressed efficiently. The experiments to verify the superiority of ODR are carried out. The result shows that machining with ODR tool has less thrust force and less processing damage compares with end mill.

Evaluation of thrust force and delamination in drilling of CFRP by using active spring restoring backup force

Carbon fiber reinforced epoxy composites are typically difficult to machine due to their anisotropic properties which cause delamination and other damages. Introducing a backup plate beneath the workpiece during drilling has proven to be an efficient and cost-effective strategy to circumvent this problem. With a view to reduce the serious fiber pull-out and delamination problems that occur during conventional drilling of CFRP composites, a novel method of active spring restoring backup force is introduced at the bottom side of the workpiece. The thrust force and delamination are determined experimentally during the drilling of holes at various drilling parameters, with and without back-up force. This spring restoring active backup force technique aids in the continuous hole making process and is found to be a simple, inexpensive and versatile technique to adopt for reducing drilling damages. The applied active backup force contributes in the reduction of delamination even at higher thrust force. The optimal backup force is found to be 321.6 N which results in reduced delamination in drilling of composite laminate.

Drilling of CFRP with Reduced and Non-Directional Heat-Affected Zone by Using 3-kW CW Single-Mode Fiber Laser

Drilling of CFRP with Reduced and Non-Directional Heat-Affected Zone by Using 3-kW CW Single-Mode Fiber Laser

Comparative Assessment of Delamination control techniques in Conventional drilling of CFRP

Composite laminates are used in many applications, such as aerospace structures, pressure vessels and automobiles due to their extremely high strength to weight ratio and corrosion resistance properties. The assembly of these materials is accomplished via fastening for which precise holes are required. It may be noted that the composite laminates are difficult to machine materials, which results into low drilling efficiency and drilling-induced delamination. Hence, it is important to develop innovative drilling processes to overcome the difficulties related in machining of composite materials. This paper presents a comprehensive study involving experimental characterization to understand the effect of cutting parameters on the extent of delamination during conventional drilling of carbon fiber reinforced polymer. Some processing parameters, such as feed rate play a dominant role in delamination as compared to spindle speed. A comparative study of different techniques for controlling the delamination in conventional drilling process, such as back up plate, pre-drilled pilot hole and peck drilling has also been conducted. The analysis shows that the peck drilling yields lower delamination extent, thrust force, hole size variation and hole surface roughness.

Multi-objective optimization of CFRP drilling parameters with a hybrid method integrating the ANN, NSGA-II and fuzzy C-means

A full factorial experiment is performed for the conventional dry drilling of CFRP with spindle speed, feed rate and point angle as drilling parameters, response variables are thrust force and exit-delamination. Artificial neural network (ANN) is developed to express thrust force and delamination factor as a function of drilling parameters. Multi-objective optimization of drilling parameters is accomplished based on Non-dominated Sorting Genetic Algorithm (NSGA-II) with thrust force, delamination factor and material removal rate as optimization objectives, delamination factor also serves as a constraint. The Pareto front of drilling response variables determined by NSGA-II consists of a large number of non-dominated solutions. In order to facilitate the experimental verification of optimization results, fuzzy C-means clustering algorithm is used to narrow down the solutions on the front to several representative ones. Conformation tests are conducted and results show that the representative solutions can give satisfactory performance with achieving a trade-off among thrust force, exit-delamination and material removal rate.

Analysis of exit-ply temperature characteristics and their effects on occurrence of exit-ply damages during UD CFRP drilling

This paper focuses on the analysis of exit-ply temperature characteristics and the occurrence of exit-damages during drilling of UD CFRP. Different diameter drills are used to reveal their effects on temperature variation, cutting mechanism and damage modes. The results show that exit-ply temperature is strongly dependent on the interaction between tool-workpiece system. In particular, an significant factor to affect the peak temperature is the location of unruptured region when main cutting edges act on exit-plies, which will result in high temperature appearing along hole edge at θ ~ 0°. The two-dimensional maps of high temperature along borehole edge are drawn at a continuous change of fiber cutting angles, based on which the dependences of exit-damages on the cutting temperature variations are discussed for the first time. The effects of high temperature on the exit-ply hole wall damages are concluded by examining the micrographs. And the width of loose surface near the hole-exit is identified to represent the functioning range of the excessive temperature. Moreover, the effects of high temperature on the exit-delaminations are analyzed by the adjusted delamination factor (Fda) at various drilling parameters.

Defect suppression mechanism and experimental study on rotary ultrasonic-assisted drilling of CFRP

Defect suppression mechanism and experimental study on rotary ultrasonic-assisted drilling of CFRP

Optimization of Process Parameters in Drilling of CFRP Reinforced with Different Percentage of Si3N4 using Taguchi Method

Optimization of Process Parameters in Drilling of CFRP Reinforced with Different Percentage of Si3N4 using Taguchi Method

Finite Element Analysis of Drilling of CFRP Reinforced with Different Percentage of Si3N4

Finite Element Analysis of Drilling of CFRP Reinforced with Different Percentage of Si3N4