Machining Of Carbon Fiber Reinforced Polymer Research Articles

Experimental study on manufacturing of vacuum-brazed grinding tools with diamond grains

AbstractThis work provides an experimental study on manufacturing methods for vacuum-brazed diamond grinding for edge machining of carbon fiber-reinforced polymers (CFRP). Therefore, various methods for applying active brazing alloys and diamond grains were investigated. The application methods were evaluated regarding practicability and the possibility of automation. Additionally, the samples were examined after vacuum brazing and brazing results were compared concerning method, amount and type of brazing alloy, diamond grains and binding agent. It was found that the best results could be achieved by using fluidized bed coating for diamond application and a brazing alloy containing a 15% binding agent. The method and brazing alloy were then used to produce cylindrical mounted points for grinding tests. It was possible to show that vacuum-brazed tools performed as good as commercially available electroplated tools.

Partition five-axis surface machining of CFRP laminate structures considering fiber orientation

ABSTRACT Carbon Fiber Reinforced Polymer (CFRP) is commonly employed in advanced industries, acclaimed for their outstanding mechanical properties. The inherent anisotropy of CFRP necessitates careful consideration of the Fiber Cutting Angle (FCA) to achieve optimal surface quality during machining, a challenge that intensifies with curved surface components due to the continuous variability of FCA. In the machining of CFRP curved surfaces, the presence of local singularity precipitates abrupt changes in tool orientation, adversely affecting surface integrity and machining efficiency. To solve this problem, this study proposed a toolpath partitioning method specifically designed for the machining of CFRP curved surfaces, aiming to mitigate the effects of local singularity. Additionally, a novel tool positioning strategy accounting for dual fiber orientations in the machining of bidirectional CFRP curved surfaces was developed. The practical applicability of these methodologies was assessed through the manufacturing of an internal fixation plate via 5-axis machining of bidirectional CFRP laminates. Comparative microscopic observations and surface profile assessments demonstrate a marked improvement in surface quality relative to traditional 3-axis machining, alongside a 25% reduction in machining time compared to 5-axis machining processes absent the partitioning method.

Force model of ultrasonic empowered minimum quantity lubrication grinding CFRP

As a weight-reducing material in aerospace applications, carbon fiber reinforced polymer (CFRP) requires precision grinding to ensure the accuracy and assembly of mating positioning surfaces. However, achieving low-damage machining of CFRPs remains challenging. Flood cooling reduces the mechanical properties, while dry grinding deteriorates the surface integrity, making minimum quantity lubrication (MQL) a viable alternative. However, nanolubricants struggle to penetrate the grinding area due to gas barrier obstruction. Consequently, a new CFRP grinding approach using multiangle 2D ultrasonic vibration-empowered nanolubricant MQL was proposed. An analytical force model is crucial for optimizing machining strategies and adjusting parameters. The aim is to reveal grinding mechanics and develop a force model under different ultrasonic and lubrication-cooling conditions. First, a uniform random fiber distribution model and a grinding wheel model were established, and the mechanical properties of the interface were predicted. Then, the intermittent grinding behavior and dynamic stiffnesses of the multiangle 2D ultrasonic vibration-assisted grinding (UVAG) system were investigated based on the geometric kinematics of the grains' trajectory. Furthermore, based on the deformation deflection curve, bending fracture force models for 45°, 90°, and 135° fibers were established with different contact and boundary conditions. The material removal mechanisms of shear and tension-compression buckling in 0° CFRP grinding were revealed, and an elliptical contact normal force model was established. The interlayer shear in 45° CFRPs was analyzed. The longitudinal compressive matrix cracking and fiber shear fracture in the 90° CFRPs were elucidated. Fiber microbuckling and fiber bundle removal of 135° CFRPs were investigated. Finally, grinding force models with different fiber orientation angles (FOAs) were interconnected and experimentally assessed. Experimental assessments demonstrated that the grinding force model has acceptable estimation error and effectively captures the mechanics of CFRPs with different FOAs.

A unified geometrical modeling and analysis method for evaluating CFRP machining performance: Cutting geometry space

Carbon Fiber Reinforced Polymer (CFRP) is extensively utilized in the cutting-edge industries, attributed to its superior mechanical performances. The machining performance of CFRP, however, is significantly influenced by its pronounced anisotropy, particularly the fiber orientation. Consequently, Fiber Cutting Angle (FCA) is widely employed to assess the relationships between cutting geometry and machining performance, yet the coupling of cutting orientation and fiber orientation, along with the absence of feeding angle, limits the further exploration into the underlying mechanisms. This article introduced a novel geometrical framework termed “Cutting Geometry Space” (CGS), for modeling CFRP machining process. Incorporating feeding orientation, cutting orientation and fiber orientation, CGS is applied in milling process for an enhanced comprehension of cutting geometry. Additionally, a pragmatic milling experiment is designed, efficiently evaluating the performances of 1092 combinations of CGS parameters in 13 T700-12K/epoxy CFRP specimens. Microscopical observations and morphological analyses reveals four predominant fracture mechanisms in CFRP machining, with fiber-matrix debonding and bending-induced fracture identified as the key contributors to macroscopic cavity formation. A designated "Damage Zone" within the CGS, encompassing a cutting angle range of 90°–270° and a fiber tilt angle of 15°–60°, is identified as a high-risk area for machining-induced surface cavities. Additionally, the impact of feeding orientation on the surface integrity is confirmed and explained by the influence on the equivalent FCA. Furthermore, the study elucidates chatter marks as a phenomenon induced by a confluence of factors, including generalized down milling, high FCA, and a significant effective cutting fiber count. The observed shift in chatter mark with varying feeding angles provides deep insights into the complex dynamics of machining parameters.

Effects of Failure Criteria on Quantitatively Determining the Machining Mechanics for CFRP with Different Tool Rake Angles

Abstract The machining mechanics of carbon fiber reinforced polymer (CFRP) materials is influenced by the coupled effects of the workpiece anisotropy, tool edge geometry, and cutting parameters. Predicting the chip formation mechanism is crucial for optimizing cutting parameters, reducing tool wear, and improving efficiency and surface quality. This study quantitatively evaluates the effect of main CFRP failure criteria on the chip formation mechanism in modeling the machining mechanics of CFRP. The results show that the Hashin-Puck and Davila criteria excel at capturing chip formation across all fiber orientations because of the incorporation of ‘internal friction’ concept, while others only achieve accurate predictions in specific fiber orientation ranges due to improper shear strength consideration. The sources of the prediction similarities, differences, and limitations of failure criteria are experimentally validated. Sensitivity analyses quantitatively determine the effect of the tool rake angle on the machining energy consumption and cutting forces across the fiber orientation range. This research can be used to select the optimal failure criteria, design proper cutting tool geometry, and inform the cutting parameter choices for CFRP machining operations.

Sustainable shape formation of multifunctional carbon fiber-reinforced polymer composites: A study on recent advancements

Shaping multifunctional carbon fiber-reinforced polymer (CFRP) composites has gained significant attention in recent times. This study investigates the progress made in developing environmentally friendly techniques for shaping CFRP composites. The focus is on achieving sustainable manufacturing processes while maintaining the desirable properties of CFRP composites. Therefore, this review article examines the impact of machining, tools, monitoring, and cooling techniques on CFRP composites. Delamination factors are also considered from a materials engineering standpoint. The objective is to meet diverse application needs and enhance CFRP machining processes, highlighting the importance of sustainable practices in shaping the future of composite materials.

A comparative experimental study of unidirectional CFRP high-speed milling in up and down milling with varied angles

Precision machining of Carbon Fiber Reinforced Polymer (CFRP) is challenging due to its high strength and anisotropic microstructure. This study proposes a specially designed cutting experiment method to understand the influence mechanism of cutting force and surface quality in CFRP high-speed cutting process. The study examines the influence of fiber cutting angle, up/down milling, and machining parameters on the side milling of regular 12-corner unidirectional CFRP samples. Cutting force and surface quality are evaluated to analyze the machining process. The results show that the cutting angle is a key factor influencing milling force and surface quality. For cutting along the fiber, force follows 60° > 30° > 90° > 0°, and against the fiber, it follows 90° > 180° > 150° > 120°. The 90° cutting angle provides optimal surface quality, and cutting against the fiber facilitates material removal. Up-milling can reduce cutting force by 15 %–20 % and surface roughness Sa by up to 25 % compared to down-milling, while improving tool durability. High-speed cutting can reduce surface roughness by at least 35 %. These findings can optimize CFRP machining processes and improve quality results.

Surface roughness prediction model in high-speed dry milling CFRP considering carbon fiber distribution

The surface roughness of carbon fiber-reinforced polymer (CFRP) components is extremely important because of the increasing demand for higher performance, reliability, and longer lifetime in aerospace and other manufacturing industries. However, the cutting mechanisms of CFRP are still unclear, which limits its formation mechanism prediction for surface roughness. Thus far, this study presents three action mechanisms in the CFRP machining process: accumulation bouncing on the matrix, impact effect on carbon fibers, and workpiece self-action. The workpiece self-action was reflected and calculated using the light rope model, which is new in CFRP machining. Furthermore, the formation mechanisms of surface roughness were first elucidated in the high-speed dry (HSD) milling of CFRP. An accurate surface roughness prediction model was theoretically formulated considering the kinematics, dynamics, and carbon fiber distribution. Surface roughness was expressed as the three-dimensional arithmetic mean height. The surface roughness prediction model was established and confirmed to have a high prediction accuracy of 90.05%, demonstrating that the distribution of carbon fibers was the main influencing factor of the surface roughness. Moreover, nonlinear regression analysis was used to clarify the effects of cutting parameters on the surface roughness, impact effect, and relationship between the surface roughness and impact effect. The study verified the feasibility of HSD milling CFRP, and it also provided guidance for breaking the low-speed machining limits by improving the machining process.

Study of the surface integrity during CFRP trimming: Tool material and geometry, fiber orientation and tool wear effect analysis

Trimming operation of CFRP (Carbon Fiber Reinforced Polymer) high performance components is highly relevant to shape the final part geometry in aerospace industry. Nevertheless, due to the anisotropic nature of this composite materials and the high abrasiveness of the carbon fibers, machining of CFRP is usually accompanied by rapid tool wear and surface defects. Delamination, fiber pull-out or even resin overheating are some of the most common surface issues that can result in time-consuming and costly post-machining and in some cases leads to rejection of components. Therefore, the correct tool selection, cutting conditions and machining strategy plays an essential role. In this context, the present paper introduces a surface integrity study where the effect of different tool material (PCD and CVD-Diamond coated), tool geometry, fiber orientation and tool wear levels are analyzed. Trimming tests are performed in aerospace relevant HexPly® M21E/34%/UD134/IMA-12K material and the surface integrity is examined via optical microscope. The results of this study provide an important foundation for characterizing the material machinability and develop a process planning tool for the optimization of the machining procedure and tool selection to avoid surface defects leading to a significant increase in the quality of components.

Recent trends in drilling of carbon fiber reinforced polymers (CFRPs): A state-of-the-art review

The machining of CFRP is a very fascinating topic nowadays. Carbon fiber reinforced polymers are in widespread use due to their excellent properties such as high corrosion resistance, high strength to weight ratio, low thermal expansion, high fatigue strength, and high stiffness to weight ratio. To satisfy the various necessities of the applications, machining of CFRP is required. The drilling process possesses great importance to facilitate the component assemblies. The challenging part is to complete the drilling of CFRP without generation of the delamination damage and other defects which is the main reason for the rejection of machined parts in the industry. However, it can be achieved by adequate tool geometry, cutting parameters, by putting two rigid plates on each side of the workpiece or with high-speed drilling. In the present study, the literature review of several kinds of research has been encapsulated. Various machining aspects such as induced thrust force and torque, tool wear, surface roughness, and hole quality, surface defects and delamination, the effect of cutting parameters, and effect of tool geometry on output responses have been in detail discussed. Furthermore, various proposed delamination factors have been included in this study.

Multi-objective optimization of carbon fiber–reinforced polymer drilling process based on grey fuzzy reasoning grade analysis

With outstanding mechanical advantages such as high strength, light weight, high rigidity, low thermal expansion, good resistance corrosion, and high vibration resistance, carbon fiber–reinforced polymer (CFRP) is becoming increasingly popular in the automotive, aerospace, and medical spheres. For the CFRP machining, the biggest drawback is the effect of moisture on the mechanical properties caused by the cooling liquid and tool geometry. The appreciable body of study on the influence of wetness on the mechanical quality of carbon fiber–reinforced plastic has shown that there is no suitable use for lubrication fluids in the composite industry. However, there is a significant impact on the CFRP machining capabilities caused by the geometry of the cutting tool and cryogenic liquid cooling. This paper investigated the optimal choice of the parametric combinations in the CFRP drilling process. The optimization method was proposed using the Fuzzy interference system based on grey relation analysis. The experiment data was designed according to the Taguchi method. The twist angle of the drill, the coolant gas, and the feed rate were considered as the parameter inputs while observing several multi-responses such as thrust force and temperature generated during drilling process. The optimal result, as well as the case with highest grey fuzzy reasoning grade (GFRG), indicated that the low feed rate combined with the high twist angle drill in the hybrid cryogenic CO2-N2 gas condition tended to minimize the value of the response output. The verification experiment results showed a good correlation with the optimal analytical result. The analysis of variance results also showed that the reliability of the data was satisfactory.

Green Picosecond Laser Machining of Thermoset and Thermoplastic Carbon Fiber Reinforced Polymers.

There has been an increase in demand for the development of lightweight and high-strength materials for applications in the transportation industry. Carbon fiber reinforced polymer (CFRP) is known as one of the most promising materials owing to its high strength-to-weight ratio. To apply CFRP in the automotive industry, various machining technologies have been reported because it is difficult to machine. Among these technologies, picosecond laser beam-induced machining has attracted great interest because it provides negligible heat transfer and can avoid tool wear. In this work, we conducted and compared machining of 2.15 mm-thick thermoset and 1.85 mm-thick thermoplastic CFRPs by using a green picosecond laser. The optimized experimental conditions for drilling with a diameter of 7 mm led to a small taper angle (average ~ 3.5°). The tensile strength of the laser-drilled specimens was evaluated, and the average value was 570 MPa. Our study indicates that green picosecond laser processing should be considered as a promising option for the machining of CFRP with a small taper angle.

Mechanics analysis and predictive force models for the single-diamond grain grinding of carbon fiber reinforced polymers using CNT nano-lubricant

Abstract Machining of carbon fiber-reinforced polymer (CFRP) with less damage remains to be a challenge because of anisotropy and inhomogeneity issues. Flood cooling will reduce the mechanical properties of CFRPs due to its hygroscopicity, however, dry grinding will result in thermal damage and deterioration of surface integrity, which cause it not suitable in aeroengine and aerostructure applications. Aiming to resolve the above gaps, the grinding mechanics for a single grain of CFRPs involving CNT nano-lubricant minimum quantity lubrication (MQL) is explored. To reveal the various fundamental mechanisms in machining CFRP of special transversal grinding and lubrication conditions, four sub-models were developed based on the unique geometries of grain and fiber in contact due to the random fiber arrangements and grain edge shapes under different undeformed chip thicknesses. Specifically, the models account ⅰ) the contact force model between the grain tip and fibers, ⅱ) the local contact stress model of elliptical region between the spherical grain edge and cylindrical fiber, ⅲ) the tensile fracture force model of single fiber regarded as an bending beam fixed at both ends and constrained on the elastic foundation, and ⅳ) the extrusion and shearing force model on the cut fiber section at the grinding groove. Furthermore, the grinding force model is obtained by integrating these sub-models, in which the grain-fiber friction coefficient and grinding mechanics are accurately introduced. Finally, the model is numerically simulated and the trend of force along the entire grinding arc length is obtained. Experimental verifications demonstrate the approach for predicting the grinding force have acceptable accuracy and can successfully capture the mechanics of CFRPs. The model reveals that the tensile fracture force of single fiber has the most contributions to the grinding force.

Multi-objective optimization of hole dilation at inlet and outlet during machining of CFRP by μEDM using assisting-electrode and rotating tool

Machining of carbon fiber-reinforced polymers (CFRP) by traditional processes is quite challenging as damages namely breakage of fibers, delamination, and fiber pull-out occur during machining. Therefore, non-traditional machining process namely micro-electrical discharge machining (μEDM) is emerging to produce precise and high-quality features in CFRP. In this work, for machining CFRP, μEDM method coupled with rotary tool and assisting-electrode was used for efficient spark generation. Grey relational analysis (GRA) was performed to optimize the machining parameters viz. voltage (100, 130, 160, and 190 V), pulse duration (10, 20, 30, and 40 μs), and tool speed (200, 300, 400, and 500 RPM) that affect the output responses namely hole dilation at inlet (HDin) and outlet (HDout). The optimal condition of input parameters was found to be V1/T1/S1 (100 V/10 μs/200 RPM). The voltage was observed to be the most affecting factor with a contribution of 90.95% while tool speed and pulse duration had a contribution of 5.91% and 1.48%, respectively. It was also found that the material removal mechanism was a complex phenomenon where sparking occurred both at end face and side surface of the tool. The deposition of pyrolytic carbon particles that helps in continuing the sparking was observed in the micrographic images obtained through field emission scanning electron microscope (FESEM). The burning of the matrix due to thermal effect and spalling was also evident which led to the removal of the material from the composite.

Investigation of CFRP cutting mechanism variation and the induced effects on cutting response and damage distribution

Machining of carbon fiber-reinforced polymers (CFRP) still remains a difficult procedure in the whole manufacturing process. One of the reasons is the cutting mechanism varies during machining, causing the inconsistency of surface integrity. This study intends to investigate the continuous variation of cutting mechanism and the induced cutting responses and damages. A novel experiment, with square and circular workpieces involved in cutting, was designed. A three-dimension micro-scale cutting simulation model was built. The experiment and simulation were combined to analyze the evolution and the correlation of cutting forces, machined surface roughness, sub-surface damage and the burr formation. The effects of rake angle and tool edge radius on chip formation and sub-surface damage were also presented. The conclusions are helpful to understand the damages generation during machining of CFRP.

An application of non-ordinary state-based peridynamics theory in cutting process modelling of unidirectional carbon fiber reinforced polymer material

The usage of carbon-fiber-reinforced polymer (CFRP) composite keeps increasing in modern industries. However, because of the complexity of CFRP structure, the analysis for CFRP failure process, especially for machining process, is quite difficult. This paper presents a non-ordinary state-based peridynamic approach that can be applied to CFRP machining analysis. In order to describe the composite’s anisotropy, fiber bond and matrix bond is first introduced in this approach. For describing the failure characteristic of composite, the Maximum stress failure criteria and Hashin failure criteria is then incorporated into the state-based peridynamic approach. Finally, the contact state between tool and workpiece is detected by utilizing the penalty method in modeling the machining process. To demonstrate the effectiveness of the present method, tension and cutting experiments are conducted as well.

Machining quality and cutting force signal analysis in UD-CFRP milling under different fiber orientation

Increasing usage of carbon fiber-reinforced polymer (CFRP) components in the airplane industry has led to higher demand in the machining quality of CFRP. In order to meet the quality requirements of final assembly, the signal monitoring of various processing parameters can be used to ensure the machining setup in perfect order. In the present work, a set of experiments for UD-CFRP side milling has been carried out with different fiber cutting angle. The effects of fiber cutting angle on machining surface quality as well as the corresponding milling force signal features have been investigated based on time, frequency domain analysis, and wavelet analysis methods. The analysis results demonstrate that, for the against fiber cutting condition, the cutting force signal has a significant increase for high-frequency component energy percentage, and the higher frequency components are more sensitive. In addition, the fluctuation trend of power percentage for frequency band S3 (1500–2500 Hz) and surface roughness is quite close, which can be employed as a monitoring index for CFRP machining surface roughness.

A review on machinability of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) composite materials

Abstract Fiber reinforced polymer (FRP) composite materials are heterogeneous and anisotropic materials that do not exhibit plastic deformation. They have been used in a wide range of contemporary applications particularly in space and aviation, automotive, maritime and manufacturing of sports equipment. Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) composite materials, among other fiber reinforced materials, have been increasingly replacing conventional materials with their excellent strength and low specific weight properties. Their manufacturability in varying combinations with customized strength properties, also their high fatigue, toughness and high temperature wear and oxidation resistance capabilities render these materials an excellent choice in engineering applications. In the present review study, a literature survey was conducted on the machinability properties and related approaches for CFRP and GFRP composite materials. As in the machining of all anisotropic and heterogeneous materials, failure mechanisms were also reported in the machining of CFRP and GFRP materials with both conventional and modern manufacturing methods and the results of these studies were obtained by use of variance analysis (ANOVA), artificial neural networks (ANN) model, fuzzy inference system (FIS), harmony search (HS) algorithm, genetic algorithm (GA), Taguchi's optimization technique, multi-criteria optimization, analytical modeling, stress analysis, finite elements method (FEM), data analysis, and linear regression technique. Failure mechanisms and surface quality is discussed with the help of optical and scanning electron microscopy, and profilometry. ANOVA, GA, FEM, etc. are used to analyze and generate predictive models.

Effects of atomization-based cutting fluid sprays in milling of carbon fiber reinforced polymer composite

Carbon Fiber Reinforced Polymers (CFRP) are considered hard to cut materials, because of the abrasiveness of carbon fibers and the low transverse strength of the composite layers that leads to delimitation under machining forces. The application of cutting fluid is a common way of reducing tool wear and machining forces in machining of metallic materials, yet this solution cannot be applied in machining of CFRP, because moisture damages the structural integrity of the composite workpiece. In this paper, an experimental study is conducted to examine the feasibility and effectiveness of applying atomized cutting fluid in milling of CFRP. In the studied atomization-based method, the cutting fluid is broken down into micrometer size droplets that are sprayed directly into the cutting zone. In the presented study, two types of cutting fluids, general purpose semisynthetic coolant and vegetable oil, are applied by atomization, and their performances in reducing cutting forces, tool wear, surface roughness, and delamination are studied over a range of cutting speeds and feed rate values.

Impact of Cryogenic Condition and Drill Diameter on Drilling Performance of CFRP

Machining of carbon fiber-reinforced polymer (CFRP) is a rather hard task due to the inhomogeneity and anisotropy of this material. Several defects occur in the material when CFRP is machined and machining quality deteriorates owing to these material properties. In recent years, liquid nitrogen has been considered an environmentally safe, clean, and non-toxic coolant used to cut various materials in order to enhance machinability and prevent damage during machining. In this study, a new, eco-friendly cryogenic machining technique called dipped cryogenic machining was applied for the drilling of CFRP. This experimental study investigated the effect of feed rate and drill diameter on the thrust force, delamination factor, surface quality and drill wear. Machined surfaces were analyzed in detail using a scanning electron microscope and atomic force microscope. Results indicated that the drilling of CFRP with the dipped cryogenic machining approach greatly improved machinability by reducing the surface roughness of the drilled parts and tool wear. However, it increased the thrust force and delamination factor.