Carbon Fiber-reinforced Plastic Composite Materials Research Articles

Multi optimization in slot milling of CFRP composites through grey relational- based Taguchi analysis

Carbon fiber-reinforced plastic (CFRP) composite materials are challenging to machine due to their anisotropy and heterogeneity. Thus, the experimental study of milling CFRP composite material is very crucial. In the current study, based on Taguchi’s L9 orthogonal array, slot milling experiments were performed on CFRP composite samples to make a decision on a parametric optimization of multiple responses such as material removal rate (MRR), delamination factor (Fd) and surface roughness (Ra) using grey relational-based Taguchi analysis. The selected milling parameters are cutting speed (A), feed (B), and depth of cut (C). Based on Grey Relational Grade (GRG), Analysis of Variance (ANOVA) was used to determine the parameters' significant contributions and the parameters' optimal levels. The results showed, with a 95% confidence level, that all of the chosen cutting parameters have a substantial impact on all of the measured responses. Based on a confirmatory test performed under ideal milling conditions, MRR has been increased with an improvement of 31.25 %, Fd has been decreased with an improvement of 1.66% and Ra has been decreased with an improvement of 28.3%. These improvements in all measured responses are equivalent to an improvement of GRG by 3%.

The Effect of Clearance Angle on Tool Life, Cutting Forces, Surface Roughness, and Delamination during Carbon-Fiber-Reinforced Plastic Milling.

This study aimed to investigate the effect of the clearance angle of the milling tool on wear, cutting forces, machined edge roughness, and delamination during non-contiguous milling of carbon-fiber-reinforced plastic (CFRP) composite panels with a twill weave and 90° fiber orientation. To achieve the objective of the study, it was first necessary to design suitable tools (6 mm diameter sintered carbide shank milling cutters) with a variety of clearance angles (8.4°, 12.4°, and 16.4°) and all the machinery and measuring equipment for the research to be carried out. Furthermore, measurement and evaluation methods for cutting tool wear, cutting forces, machined edge roughness, and delamination were developed. Last but not least, the results obtained during the research were summarized and evaluated. From the experiments conducted in this study, it was found that the tool clearance angle has a significant effect on tool wear, roughness of the machined surface, and delamination of the carbon fiber composite board. The tool with a clearance angle of 8.4° wore faster than the tool with a clearance angle of 16.4°. The same trend was observed for cutting force, machined surface roughness, and delamination. In this context, it was also shown that the cutting force increased as the tool wear increased, which in turn increased surface roughness and delamination. These results are of practical significance, not only in terms of the quality of the machined surface but also in terms of time, cost, and energy savings when machining CFRP composite materials.

Effects of Cryogenically Treated CFRP Composite on the Buckling Behavior in the Adhesively Bonded Beam

Carbon fiber reinforced plastic (CFRP) composite materials have favorable mechanical and physical properties such as low density, high strength-to-weight ratio, high fatigue resistance and high creep behavior, and high stiffness. Thanks to these unique properties, they produce aircraft parts such as outer flaps, carry-through structures, and center wing boxes and automotive parts such as body panels, engine components, and structure members. However, studies have been continuously performed on improving the properties of CFRP composite materials. Recently, investigation of the effects of cryogenic (LN2) cooling on the mechanical behavior and characteristic of these composite materials is getting a popular and important issue. In this sense, this study aims to examine the buckling behaviors of adhesively bonded beam-produced cryogenically treated carbon fiber reinforced plastic (Cryo-CFRP), CFRP, steel, and aluminum. Therefore, a new finite element model was adopted to evaluate the buckling capacity of Cryo-CFRP composite material in the adhesively bonded beam. The model is a supported adhesive beam subject to two opposite-edge compressions until the material buckles. The elastic, homogeneous adhesive was used in the assembly. Finite element models for the adhesively bonded beam having four different adherents (CRFP, Cryo-CFRP, steel, and aluminum) were established by ANSYS® software. The critical buckling loads of the adhesively bonded beam were predicted, and their mode shapes were presented for the first six modes. The effects of the usage of Cryo-CFRP on the critical buckling load were investigated. Among the adherents’ materials, the highest critical buckling load was determined for Cryo-CFRP/Steel adhesively bonded beam as 23.6 N. This value was obtained as 22.3 N for CFRP/Steel adherent samples. Thus, the critical buckling load was increased by 5.6 % when one adherent steel was constant and the other adherent material changed from CFRP to Cryo-CFRP. Also, the critical buckling load increased by 3.7 % when using a cryogenically treated Cryo-CFRP/Aluminum couple instead of a CFRP/Aluminum couple in the sandwich beam. The findings demonstrated that the cryogenic treatment positively affects the buckling behavior in the adhesively bonded beam.

The development of an ultrasonic vibration hand-held pneumatic drill for hole-machining on CFRP composite materials

Carbon fiber reinforced plastic (CFRP) composite materials are widely adopted for manufacturing aircraft. In aircraft assembly process, millions of bolt and rivet holes need to be machined on site, and most of them are drilled by manual operations with hand-held pneumatic drill. It is well known that unstable operations easily are caused in manual operations, which results in serious defects on CFRP materials. These defects drastically reduce fatigue resistance of aircraft. To improve the quality of drilling holes, an ultrasonic vibration hand-held pneumatic drill is developed in this study. The structure of this device was designed, and its vibration mode was analyzed with finite element method. A real ultrasonic vibration hand-held drill was produced and its vibration performance was measured. Drilling experiments on CFRP materials are implemented. The results show that, with the developed hand-held drill device, the shakes of hand decrease by 35–43% and thrust forces decrease by 23%. The defects of matrix resin peel-off and delamination during drilling process are significantly reduced. This study provides a novel equipment for drilling hole on aircraft assembly site.

Application of Carbon fiber-reinforced plastic composite material in automotive bumper

The emission problem of these traditional gasoline vehicles has become more and more serious. To reduce emission, an important method is to reduce the weight of the car. In this study, a standard model of a vehicle bumper is used to conduct the experiment on lightweight bumper design. The material simulated in the model of the bumper is CFRP material. The angle of each laminate of CFRP material and the layout of the laminate structure contains six layers are modeled in Hypermesh software. Then CFRO material is used to replace the traditional aluminum and reduce the weight of the front bumper component.

Resistive loss considerations in the finite element analysis of eddy current attenuation in anisotropic conductive composites

The penetration depth of eddy current is widely recognized as a guide in the nondestructive testing (NDT) methods using eddy current, which is often treated as equivalent to the skin effect depth. This paper takes the resistive loss of eddy current into account, and clearly points out the discrepancy between the two terms, especially in the case of carbon fiber reinforced plastic (CFRP) composites, which are less conductive and show strong anisotropy. Based on the theoretical modeling of skin depth and resistive loss according to Poynting's theorem, this paper adopts finite element numerical simulation to study the attenuation characteristics of current density and magnetic field strength under the conditions of different conductivity, frequency and anisotropy ratio. In addition, a set of experiments are conducted to verify the simulation results semi-quantitatively. The results show that the resistive loss dominates the eddy current attenuation in less conductive and high anisotropic composites, resulting in a frequency independent attenuation law, which is very different from skin effect. Meanwhile, the resistive loss in the orthotropic laminate is greatly reduced due to the existence of the interface between the adjacent layers. This research provides a theoretical basis for the realization of high frequency eddy current testing method for anisotropic CFRP composite materials.

Surface quality optimization of CFRP plates drilled with standard and step drill bits using TAGUCHI, TOPSIS and AHP method

Purpose Drilling of carbon fiber reinforced plastic (CFRP) composite plates with high surface quality are of great importance for assembly operations. The article aims to optimize the drill geometry and cutting parameters to improve the surface quality of CFRP composite material. In this study, CFRP plates were drilled with uncoated carbide drill bits with standard and step geometry. Thus, the effects of standard and step drill bits on surface quality have been examined comparatively. In addition, optimum output parameters were determined by Taguchi, ANOVA and multiple decision-making methods. Design/methodology/approach Drill bit point angles were selected as 90°, 110° and 130°. In cutting parameters, three different cutting speeds (25, 50 and 75 m/min) and three different feeds (0.1, 0.15 and 0.2 mm/rev) were determined. L18 orthogonal sequence was used with Taguchi experimental design. Three important output parameters affecting the surface quality are determined as thrust force, surface roughness and delamination factor. For each output parameter, the effects of drill geometry and cutting parameters were evaluated. Input parameters affecting output parameters were analyzed using the ANOVA method. Output parameters were estimated by creating regression equations. Weights were determined using the analytic hierarchy process (AHP) method, and multiple output parameters were optimized using technique for order preference by Similarity to An ideal solution (TOPSIS). Findings It has been determined from the experimental results that step drills generate smaller thrust forces than standard drills. However, it has been determined that it creates greater surface roughness and delamination factor. From the Taguchi analysis, the optimum input parameters for Fz step tool geometry, 90° point angle, 75 m/min cutting speed and 0.1 mm/rev feed. For Fd, are standard tool geometry, 90° point angle, 25 m/min cutting speed and 0.1 mm/rev feed and for Ra, are standard tool geometry, 130° point angle, 25 m/min cutting speed and 0.1 mm/rev feed. ANOVA analysis determined that the most important parameter on Fd is the tip angle, with 56.33%. The most important parameter on Ra and Fz was found to be 40.53% and 77.06% tool geometry, respectively. As a result of the optimization with multiple criteria decision-making methods, the test order that gave the best surface quality was found as 4–1-9–5-8–17-2–13-6–16-18–15-11–10-3–12-14. The results of the test number 4, which gives the best surface quality, namely, the thrust force is 91.86 N, the surface roughness is 0.75 µm and the delamination factor is 1.043. As a result of experiment number 14, which gave the worst surface quality, the thrust force was 149.88 N, the surface roughness was 3.03 µm and the delamination factor was 1.163. Practical implications Surface quality is an essential parameter in the drilling of CFRP plates. Cutting tool geometry comes first among the parameters affecting this. Therefore, different cutting tool geometries are preferred. A comparison of these cutting tools is discussed in detail. On the other hand, thrust force, delamination factor and surface roughness, which are the output parameters that determine the surface quality, have been optimized using the TOPSIS and AHP method. In this way, this situation, which seems complicated, is presented in a plain and understandable form. Originality/value In the experiments, cutting tools with different geometries are included. Comparatively, its effects on surface quality were examined. The hole damage mechanism affecting the surface quality is discussed in detail. The results were optimized by evaluating Taguchi, ANOVA, TOPSIS and AHP methods together.

Stability and Load-Carrying Capacity of Thin-Walled FRP Composite Z-Profiles under Eccentric Compression.

This study investigates the effect of eccentric compressive load on the stability, critical states and load-carrying capacity of thin-walled composite Z-profiles. Short thin-walled columns made of carbon fiber-reinforced plastic composite material fabricated by the autoclave technique are examined. In experimental tests, the thin-walled structures were compressed until a loss of their load-carrying capacity was obtained. The test parameters were measured to describe the structure’s behavior, including the phenomenon of composite material failure. The post-critical load-displacement equilibrium paths and the acoustic emission signal enabling analysis of the composite material condition during the loading process were measured. The scope of the study also included performing numerical simulations by finite element method to solve the problem of non-linear stability and to describe the phenomenon of composite material damage based on the progressive failure model. The obtained numerical results showed a good agreement with the experimental characteristics of real structures. The numerical results are compared with the experimental findings to validate the developed numerical model.

Smart Multi-Sensor Monitoring in Drilling of CFRP/CFRP Composite Material Stacks for Aerospace Assembly Applications

Composite material parts are typically laid out in near-net-shape, i.e., very close to the finished product configuration. However, further machining processes are often required to meet dimensional and tolerance requirements. Drilling, edge trimming and slotting are the main cutting processes employed for carbon fiber-reinforced plastic (CFRP) composite materials. In particular, drilling stands out as the most widespread machining process of CFRP composite parts, chiefly in the aerospace industrial sector, due to the extensive use of mechanical joints, such as rivets, rather than welded or bonded joints. However, CFRP drilling is markedly challenging: due to CFRP abrasiveness, inhomogeneity and anisotropic properties, tool wear rates are inherently high leading to superior cutting forces and detrimental effects on workpiece surface quality and material integrity. Damage such as delamination, cracks or matrix thermal degradation is often observed as the result of uncontrolled tool wear or improper machining conditions. Sensor monitoring of drilling operations is, therefore, highly desirable for process conditions’ optimization and tool life maximization. The development of this kind of automated control technologies for process and tool state evaluation can notably contribute to the reduction of scraps and tool costs as well as to the improvement of process productivity in the drilling of CFRP composite material parts. In this paper, multi-sensor process monitoring based on thrust force and torque signal detection and analysis was applied during drilling of CFRP/CFRP laminate stacks for the assembly of aircraft fuselage panels with the scope to evaluate the tool wear state. Different signal-processing methods were utilised to extract diverse types of features from the detected sensor signals. A machine-learning approach based on an artificial neural network (ANN) was implemented to make smart decisions on the timely execution of tool change, which is highly functional for CFRP drilling process automation.

Effect of Surface Roughness on the Bonding Strength and Spring-Back of a CFRP/CR980 Hybrid Composite

Carbon fiber-reinforced plastic (CFRP), which is a light and composite material, has a higher specific strength and stiffness than metal materials. However, owing to its low elongation, it is vulnerable to local impacts such as collision. Therefore, hybrid composite materials that can overcome the disadvantages of homogeneous materials by bonding CFRP and metal materials are increasingly popular. In this study, a physical surface treatment sandblast process was applied on a high tensile steel plate (CR980) manufactured by cold rolling to form another surface condition, and the bonding strength with CFRP was measured. In addition, spring-back due to the manufacturing process of the CFRP and CR980 hybrid composite material bonded with different surface roughness was observed. The bonding strength and the spring-back angle of the CFRP/CR980 hybrid composite material tended to increase with the increase in the surface roughness.

Cutting force and hole quality analysis in micro-drilling of CFRP

ABSTRACTMicro-drilling in carbon fiber reinforced plastic (CFRP) composite material is challenging because this material machining is difficult due to anisotropic, abrasive and non-homogeneous properties and also downscaling of cutting process parameters affect the cutting forces and micro-drilled hole quality extensively. In this work, experimental results based statistical analysis is applied to investigate feed and cutting speed effect on cutting force components and hole quality. Analysis of variance based regression equation is used to predict cutting forces and hole quality and their trend are described by response surface methodology. Results show that roundness error and delamination factor have similar trends to those of radial forces and thrust force, respectively. Non-linear trends of cutting forces and hole quality errors are observed during downscaling of the micro-drill feed value. Optimization results show that cutting forces and hole quality errors are minimum at a feed value which is almost equal to the tool edge radius rather than at the lowest feed value. Therefore, the presented results clearly show the influences of size effects on cutting forces and hole quality parameters in micro-drilling of CFRP composite material.

탄소섬유 복합재를 이용한 경량 착용형 로봇의 개발

In this paper, we evaluate structural integrity of the wearable robot by using finite element analysis, which is made of CFRP(Carbon Fiber Reinforced Plastic) composite materials to be lightened. On the basis of the ASTM(American Standard Test Method), mechanical tests of the material are carried out in tensile, compressive and shear test for analytical evaluation. With the tested composite material, the main frame and two femoral frames of the robot is redesigned to satisfy the lightening design requirements. It is verified with the structural analysis that the redesigned frames are good for the part of the wearable robot.

Cryogenic cooling-induced process performance and surface integrity in drilling CFRP composite material

There has been a substantial growth in using carbon fiber-reinforced plastic (CFRP) composite materials in aerospace and automotive industries due to their superior properties. This experimental study presents results from a comprehensive and systematic study investigating the effects of cryogenic cooling on drilling performance and surface integrity characteristics of CFRP composite material. Experimental data on cutting edge radius of drill bit, outer corner wear of drill bit, trust force, torque, delamination factor, and surface integrity characteristics, including borehole subsurface damage and diameter error of drilled hole, are presented and analyzed comparing dry drilling with cryogenic cooling of CFRP composite material. The findings demonstrate that cryogenic cooling has a profound effect on reducing the cutting edge rounding of drill bit and outer corner wear; it also helps enhancing the surface integrity characteristics of produced hole. However, cryogenic cooling generates larger thrust force, torque, and thus larger delamination factor.

Study on Laser Cutting Carbon Fibre Reinforced Composites

In order to solve the problem that delamination and bur will be easily produced in the process of the carbon fiber reinforced plastic (CFRP) composites, the cutting experiment of CFRP machined by pulsed Nd:YAG laser has been carried out. In the meantime, this paper investigates the mechanism of interaction between infrared laser and CFRP composite material and the quality of kerf influenced by different laser parameters and cutting directions. The study found that choosing appropriate laser parameters and cutting direction are effective means to get smaller heat affected zone (HAZ). This paper analysis the cross section morphology of kerf .The results show that the cross section does not appear stratified phenomenon and the surface is smooth, so the feasibility that infrared laser can be used to cut CFRP composites is verified.

Charpy impact fracture characteristics of CFRP composite materials according to variations of fiber array direction and temperature

Recently, the use of Carbon Fiber Reinforced Plastic (CFRP) composite, instead of metal materials, has increased in fields that have high demand for both lightweight and high specific strength materials, such as aircraft and automobile. Composites show different characteristics according to temperature and fiber array direction. Under the operating condition, the fuselage of an aircraft is often exposed to impacts from birds, hail etc. Therefore, Charpy impact fracture characteristics of the CFRP composite according temperature and fiber array direction need to be estimated to ensure aircraft safety. In this paper, after the Charpy impact tests, fractured surfaces were analyzed to estimate the impact fracture characteristics of the CFRP composite by SEM.

Characteristics of CFRP Hydrogen Storage Vessel on Rising Temperature in the Filling Process

Different types of materials are commonly used for constructing hydrogen pressure vessels. However, carbon fiber reinforced plastic (CFRP) materials are commercially used in hydrogen vessels now a day. Commercially used aluminium liner vessel is easy to construct and posses high thermal conductivity compared to other commercially available vessels. However, compared to CFRP liner vessel, it has low strength capacity and safety factors. Therefore, now a day, CFRP liner vessels are becoming more popular in modern hydrogen vehicle systems. Moreover, CFRP vessel has light weight advantage. CFRP, although, has many desirable properties in reducing the weight and in increasing the strength, it is also necessary to keep the material temperature below 85C for maintaining stringent safety requirements. Because while filling process occurs, the temperature can be exceeded due to the compression works of the gas flow. Therefore, it is very important to optimize the hydrogen filling system for avoiding temperature rise to cross the critical limit of damaging CFRP wall vessel. Computer simulation has been conducted to characterize the CFRP storage vessel in hydrogen filling to optimize the technique. Three hydrogen vessels with different volumes and with different filling pressure have been used to characterize the temperature rise of the wall materials in filling system. The wall materials have been considered as aluminum liner material and CFRP composite materials. Supply tanks have been played important roles in supplying hydrogen in different storage tanks with different supply pressures. Gas temperatures have been measured inside representative vessels in the supply reservoirs and at the inlet to the test tank during filling. In simulation, the geometry has been simplified to a cylinder for illustration purposes. The rise in temperature of the hydrogen and the tank wall during the filling of hydrogen into the actual tank with CFRP liner has been simulated with different filling conditions at Saga University and the results have been compared with JARI (Japan Automobile Research Institute) experimental data as well.

Numerical Investigations of Ultrasonic Scattering from Voids in Composite Materials Based on Random Void Model

Ultrasonic attenuation coefficient is firstly calculated utilizing the finite difference time domain method based on a novel 2-D RVM for carbon fiber reinforced plastic (CFRP) composite materials. The results show that the void morphology has detrimental effect on ultrasonic attenuation. Even at the fixed porosity, ultrasonic attenuation coefficient fluctuates due to the randomness of void morphology in CFRP composite materials. This work significantly helps to understand ultrasonic scattering mechanism of voids and formulation of CFRP composite material properties.

553 CFRP複合材料の高速衝突貫通特性について(OS24.一般セッション(9) 複合材料からハイブリッド法まで,オーガナイズドセッション)

The CFRP (Carbon Fiber Reinforced Plastic) composite material has exquisite mechanical properties, and now becomes the substitution for aluminum alloy in a wide field. However, it is weak to external force from the antiplane because it has a strong anisotropy. Then, we experimented on a high-velocity impact under the cryogenic temperature to clarify the effect that the difference of laminating direction of the fiber exerted on the fracture behavior of CFRP in this research. AS a result, it was confirmed that the effect of the temperature, the impact velocity, and the laminating direction of the fiber exerted on the fracture behavior, and it was obtained that the finding of the impact characteristic of CFRP.

A Study on the Shear-Failure of Circular Sectioned Bridge Column Retrofitted by Using CFRP Jacketing

In this paper, analytical and experimental studies on the shear-failure and confinement of circular section RC bridge columns retrofitted by carbon fiber reinforced plastic (CFRP) jacketing were performed. An effective confined concrete constitutive model named Modified L-L Model proposed by Li et al. (Li, Y.-F., Lin, C.-T. and Sung, Y.-Y. (2003). A Constitutive Model for Concrete Confined with Carbon Fiber Reinforced Plastics, Mechanics of Materials, 35:603–619.) is introduced and used to determine the thickness of CFRP for retrofitting bridge columns, and to analyze the lateral force–displacement relationship of circular sectioned bridge columns. In the Modified L-L Model, the lateral confinement of the concrete comes from both steel reinforcement and CFRP composite material. Three 40%-scale bridge columns with shear-failure mode were tested under cyclic loading at the National Center for Research on Earthquake Engineering (NCREE). The analytical lateral force–lateral displacement relationship of bridge columns using the Modified L-L Model can predict the lateral force–lateral displacement relationship of experimental result very well, and the prediction shows that the Modified L-L Model can be used in seismic retrofit analysis. In the meantime, the performance of retrofitted bridge columns can be greatly improved by using CFRP composite material.

Some experimental investigations in the drilling of carbon fiber-reinforced plastic (CFRP) composite laminates

In this paper, a concept of delamination factor F d (i.e. the ratio of the maximum diameter D max in the damage zone to the hole diameter D) is proposed to analyze and compare easily the delamination degree in the drilling of carbon fiber-reinforced plastic (CFRP) composite laminates. Experiments were performed to investigate the variations of cutting forces with or without onset of delamination during the drilling operations. The effects of tool geometry and drilling parameters on cutting force variations in CFRP composite materials drilling were also experimentally examined. The experimental results show that the delamination-free drilling processes may be obtained by the proper selections of tool geometry and drilling parameters. The effects of drilling parameters and tool wear on delamination factor are also presented and discussed. Cutting temperature has long been recognized as an important factor influencing the tool wear rate and tool life. An experimental investigation of flank surface temperatures is also presented in this paper. Experimental results indicated that the flank surface temperatures increase with increasing cutting speed but decreasing feed rate. Optimal cutting conditions are proposed to avoid damage from burning during the drilling processes.