Carbon Fiber Reinforced Plastic Composites Research Articles

Characterization and Effects of Fiber Pull-Outs in Hole Quality of Carbon Fiber Reinforced Plastics Composite.

Hole quality plays a crucial role in the production of close-tolerance holes utilized in aircraft assembly. Through drilling experiments of carbon fiber-reinforced plastic composites (CFRP), this study investigates the impact of varying drilling feed and speed conditions on fiber pull-out geometries and resulting hole quality parameters. For this study, hole quality parameters include hole size variance, hole roundness, and surface roughness. Fiber pull-out geometries are quantified by using scanning electron microscope (SEM) images of the mechanically-sectioned CFRP-machined holes, to measure pull-out length and depth. Fiber pull-out geometries and the hole quality parameter results are dependent on the drilling feed and spindle speed condition, which determines the forces and undeformed chip thickness during the process. Fiber pull-out geometries influence surface roughness parameters from a surface profilometer, while their effect on other hole quality parameters obtained from a coordinate measuring machine is minimal.

Determination of forming procedure by numerical analysis and investigation of mechanical properties of steel/CFRP hybrid composites with complicated shapes

In this study, a hybrid composite material was fabricated by stacking carbon fiber-reinforced plastic onto CR420 plates to increase the specific strength and stiffness relative to those of thick boron steel plates and dual-phase steels. Simulations were first used to compare and evaluate the abilities of two forming processes to manufacture appropriate center-pillar reinforcements. After determining the best process, a die was prepared using computer aided engineering (CAE), and a center-pillar reinforcement was formed with a carbon fiber-reinforced plastic (CFRP)/CR420 hybrid composite. The differences in the mechanical properties of the specimens were investigated according to their position using simulations. The specimen thicknesses in the experiment and simulation were compared. Positions where the contact pressure was low could be found in the simulation. Further, the reasons for the deterioration of the mechanical properties were elucidated by observing the micro-structure. Large quantities of voids with a size greater than 50μm were found in those specimens that had a contact pressure lower than 0.5MPa. The results obtained confirm that large quantities of voids cause the mechanical properties of CFRP composites to deteriorate.

Bond strength between carbon fiber–reinforced plastic tubes and aluminum joints for racing car suspension

According to previous studies, the bond strength between the carbon fiber–reinforced plastics and metals mainly depends on the bond layer between the carbon fiber–reinforced plastic composites and the metal. This article presents the results of the experiments conducted on the tensile bond strength between the carbon fiber–reinforced plastic tubes and aluminum joints. The parameters examined in these experiments include adhesive type, surface roughness of the bonded area, and thickness and length of the bond layer. The results show that the 3M DP-460NS Off-White adhesive was suitable for our experiment. The bonded surfaces of the specimens were smoothened with a P600 sandpaper to achieve higher bond strengths with the adhesive. For the six bond thicknesses tested, a thickness of 0.2 mm was optimal for the tensile experiments. The ultimate tensile force was approximately directly proportional to the bond length.

Terahertz scanning techniques for paint thickness on CFRP composite solid laminates

Terahertz ray (T-ray) scanning applications are promising tools. The use of T-ray for nondestructive evaluation was investigated on composite materials. In this characterization procedure, electromagnetic properties, such as the refractive index, were analyzed. The estimates of properties are in good agreement with known data. We successfully demonstrated the characteristics of T-ray propagating through Carbon fiber-reinforced plastic (CFRP) composites to acquire the refractive index by using the characterized material properties. A T-ray technique was developed for measuring paint thickness on CFRP laminates. Good results were obtained from tests performed on standard paint samples with thickness starting from approximately 100 μm. The method was based on reflection mode measurement with time of flight. Another method developed for measuring paint thickness using resonance frequencies was utilized to determine paint thickness on composite laminates. The paint thickness deduced from resonance frequencies agrees well with the result obtained directly from time-domain echoes.

Twisted shape bi-stable structure of asymmetrically laminated CFRP composites

Abstract Carbon fiber reinforced plastic (CFRP) laminated composites, called bi-stable composites, are applied as soft morphing host structural component. These bi-stable composites have two cylindrical stable states which have parallel direction between fiber direction of composites and principle curvature of bi-stable shape. Their final curvature can be tailored by the initial curvature. However, the cross-ply composites have twisted shape in a certain negative initial curvature. These twisted shapes also have bi-stability. Herein, the reasons for the twisted shapes are discussed from a mechanical perspective. In addition, the twisted shape was simulated by a developed analytical model considering the discussed mechanical mechanism. The simulation results show that the CFRP laminated composites have two kinds of bi-stable states (conventional shape or twisted shape) and a mono-stable state with respect to the negative initial curvature. These analytical results were verified by comparing them with those obtained by finite element analysis (FEA).

Characterization of delaminations in composite laminates by laser ultrasonics

Abstract The influence of delaminations in the anisotropic carbon fiber reinforced plastics (CFRP) on laser- generated ultrasound is investigated. A 3D-finite element method is used to simulate the propagation of ultrasonic waves in CFRP with delaminations. The asymmetric properties and distortions as well as the wave reflection and attenuation at delamination interfaces are clearly shown. Measurements on CFRP specimens with circular delaminations above 2 mm in diameter are imaged by C-scans and correlated to the modeling results. The effects of ultrasound frequency, defect size and depth location are discussed. The results show that it is possible to decrease the influence of anisotropy in CFRP composites by choosing appropriate ultrasonic frequencies and controlling the laser parameters.

Surface grinding of carbon fiber–reinforced plastic composites using rotary ultrasonic machining: Effects of tool variables

Carbon fiber–reinforced plastic composites have many superior properties, including low density, high strength-to-weight ratio, and good durability, which make them attractive in many industries. However, due to anisotropic properties, high stiffness, and high abrasiveness of carbon fibers in carbon fiber–reinforced plastic, high cutting force, high tool wear, and high surface roughness are always caused in conventional machining processes. This article reports an investigation using rotary ultrasonic machining in surface grinding of carbon fiber–reinforced plastic composites in order to develop an effective and high-quality surface grinding process. In rotary ultrasonic machining surface grinding of carbon fiber–reinforced plastic composites, tool selection is of great importance since tool variables will significantly affect output variables. In this work, the effects of tool variables, including abrasive size, abrasive concentration, number of slots, and tool end geometry, on machining performances, including the cutting force, torque, and surface roughness, are experimentally studied. The results show that lower cutting forces and torque are generated by the tool with higher abrasive size, lower abrasive concentration, and two slots. Lower surface roughness is generated by the tool with smaller abrasive size, smaller abrasive concentration, two slots, and convex end geometry. This investigation will provide guides for tool selections during rotary ultrasonic machining surface grinding of carbon fiber–reinforced plastic composites.

Additive manufacturing of carbon fiber-reinforced plastic composites using fused deposition modeling: Effects of process parameters on tensile properties

Carbon fiber-reinforced plastic composites have been intensively used for many applications due to their attractive properties. The increasing demand of carbon fiber-reinforced plastic composites is driving novel manufacturing processes to be in short manufacturing cycle time and low production cost, which is difficult to realize during carbon fiber-reinforced plastic composites fabrication in common molding processes. Fused deposition modeling, as one of the additive manufacturing techniques, has been reported for fabricating carbon fiber-reinforced plastic composites. The process parameters used in fused deposition modeling of carbon fiber-reinforced plastic composites follow those in fused deposition modeling of pure plastic materials. After adding fiber reinforcements, it is crucial to investigate proper fused deposition modeling process parameters to ensure the quality of the carbon fiber-reinforced plastic parts fabricated by fused deposition modeling. However, there are no reported investigations on the effects of fused deposition modeling process parameters on the mechanical properties of carbon fiber-reinforced plastic composites. In the experimental investigations of this paper, carbon fiber-reinforced plastic composite parts are fabricated using a fused deposition modeling machine. Tensile tests are conducted to obtain the tensile properties. The effects of fused deposition modeling process parameters on the tensile properties of fused deposition modeling-fabricated carbon fiber-reinforced plastic composite parts are investigated. The fracture interfaces of the parts after tensile testing are observed by a scanning electron microscope to explain material failure modes and reasons.

Flow-compacted deformations coupled with thermo-chemically induced distortions in manufacturing of thick unidirectional carbon fiber reinforced plastics composites

A novel technique to predict the manufacturing process-induced distortions and deformations in thick unidirectional carbon fiber reinforced plastics laminates is detailed in this article. An integrated numerical model is developed to account for non-isothermal resin flow, related compaction, transient resin cure, and resin shrinkage effects to predict the final shape of the autoclave cured thick prepreg laminate. The associated physics are mathematically coupled to solve for the process variables interactively. The results illustrate reduction in the thickness of the laminate prior to the start of curing when initial fiber volume fractions are pre-set. This confirms that the initial transverse deformation of B-stage prepreg is due to the applied vacuum and/or pressure. Once curing initiates, deformation of the laminate due to compaction increases, proportionally, with the increase in fiber volume fraction. Furthermore, the thermo-chemical residual strains contribute to additional compaction. The final distorted shape observed in simulation of the originally flat laminate matches with the shape of the fabricated laminate with 6.6 mm thickness. A solution to minimize the distortion is discussed in detail. This procedure is extended to simulate a curved laminate’s processing; where, the shear moduli were observed to influence the final shape of the laminate. The findings are presented and deliberated in this article.

An optical method for measuring surface roughness of machined carbon fibre-reinforced plastic composites

Characterization of the damage induced by machining of fibre-reinforced composites is usually performed by measuring surface roughness. Contact-based surface profilometers are the most used equipment in industry; however, it has been found that there are performance limitations which may result when used to measure machined heterogeneous composite surfaces. In this research, surface roughness is characterised using a commercial non-contact optical method, and compared with a conventional stylus profilometer. Unidirectional and multidirectional carbon fibre laminates were edge trimmed and slot milled. The variation in surface roughness was compared using different tool types, fibre orientations and cutting parameters. Surface damage and cutting mechanisms were assessed by using scanning electron microscope images, and the suitability of roughness parameters were also analysed including: Sa, Skewness and Kurtosis. Using the optical system allowed accurate roughness calculation of individual plies on a multidirectional laminate with different fibre orientations. The research has also shown that the optical system, including the use of areal roughness parameters, can increase the accuracy of roughness measurement for machined fibrous composite surfaces and is less sensitive to measurement position than the stylus.

직교 절삭 기반 탄소섬유복합재 가공특성 관련 연구

Carbon fiber reinforced plastic (CFRP) composites have been widely used due to their great strength, stiffness and light weight. However, due to its anisotropy and inhomogeneous properties the machining process of CFRP composites is typically more complex than that of regular metals. Since there are many defects, such as delamination and tool wear during the machining process of CFRP composites, the optimization of this process is essential in improving the productivity. In this study, orthogonal machining of CFRP composites was performed to identify the machining characteristics of these materials. In addition, an experimental observation of delamination was investigated through the use of scanning electron microscopy (SEM). In these experiments, the cutting forces were measured and analyzed to determine the difference between machining of CFRP composites and metals. The comparison between the numerical models and experimental results was performed in terms of the maximum cutting forces.

Dual energy CT inspection of a carbon fibre reinforced plastic composite combined with metal components

This work is focused on the inspection of carbon fibre reinforced plastic composites (CFRP) combined with metal components. It is well known that the high absorption of metallic parts degrades the quality of radiographic measurements (contrast) and causes typical metal artefacts in X-ray computed tomography (CT) reconstruction. It will be shown that these problems can be successfully solved utilizing the dual energy CT method (DECT), which is typically used for the material decomposition of complex objects. In other words, DECT can help differentiate object components with a similar overall attenuation or visualise low attenuation components that are next to high attenuation ones. The application of DECT to analyse honeycomb sandwich panels and CFRP parts joined with metal fasteners will be presented in the article.

High-Quality End Milling of CFRP – Inclination Milling with High-Helix End Mill –

Side milling tests of CFRP (carbon fiber reinforced plastics) containing thermosetting resin are carried out by TiAlN/AlCrN-coated, H2-free DLC (diamond-like carbon)-coated, and CVD diamond-coated carbide end mills without coolant. Two types of end mills having different helix angles of 30° and 60° are used. The film thickness and surface smoothness are varied for the DLC-coated end mills. The cutting characteristics are evaluated by tool wear and surface integrity (i.e., 3D profiles of the machined surface, generation of fluffing, delamination, and pull-out of the carbon fibers). The cutting force and tool flank temperature are also examined for the two types of CFRP composites and the helix angle of the end mill. “Inclination milling,”in which the end mill is tilted so that the resultant cutting force acts parallel to the work surface, is proposed as a novel technique to be used with a high-helix angle end mill. This unique approach enables the reduction of tool wear and improves the surface integrity of machined CFRP surfaces.

A Damage-Free Machining Method for CFRP Without Feedback Control Systems

A damage-free cutting method called the constant- load feeding method is proposed as a high-precision machining method in carbon-fiber-reinforced plastic (CFRP) cutting. The constant-load feeding method can minimize cutting defects such as burrs and scuffing during diamond-saw cutting. In addition, there was no apparent cutting damage to the cutting surface from drilling with a high-speed steel twist drill. The cutting resistance was kept at a constant value during the entire process. The constant-load feeding can self-regulate the optimal tool feed rate to realize damage-free machining of CFRP composites without any feedback control systems based on the cutting-force.

Two-Layer Tool with Hardness Distribution Around Tool Edge for Reducing Cutting Forces in CFRP Machining

This study presents a method for extending the life of tools in cutting of Carbon-fiber-reinforced plastics (CFRP). In the previous study, our research group found that the use of two layer tool, which has a wear resistance distribution due to the use of a combination of two different materials with different hardnesses, is effective for decreasing cutting force during machining of CFRP composites. In the two layer tool, a narrow region of the flank face close to the tool edge and the whole of the rake face were made of a material with a relatively high wear resistance, e.g., diamond or polycrystalline diamond (PCD). In contrast, the other region of the flank face was made of a material with a relatively low wear resistance, e.g., tungsten carbide (WC-Co). In this study, based on some experiments, the effect of the thickness of high wear resistance region on the reduction effects of cutting forces was investigated.

A Review of the Radio Frequency Non-destructive Testing for Carbon-fibre Composites

Abstract The purpose of this paper is to review recent research on the applications of existing non-destructive testing (NDT) techniques, especially radio frequency (RF) NDT, for carbon-fibre reinforced plastics (CFRP) composites. Electromagnetic properties of CFRP composites that are associated with RF NDT are discussed first. The anisotropic characteristic of the conductivity and the relationship between the penetration depth and conductivity should be paid much attention. Then, the well-established RF NDT including eddy current technique, microwave technique and RF-based thermography are well categorised into four types (i.e. electromagnetic induction, resonance, RF-based thermography and RF wave propagation) and demonstrated in detail. The example of impact damage detection using the induction and resonance methods is given. Some discussions on the development (like industrial-scale automated scanning, three-dimensional imaging, short-range ultra-wideband (UWB) imaging and the radio frequency identification technology (RFID)-based NDT) are presented.

Effect of on-line ultrasonic treatment on the properties of carbon fiber reinforced plastic composites

The strength, performance, and application of carbon fiber reinforced plastic (CFRP) composites are directly affected by the interfacial bonding between fiber and resin. Wet winding technology is a commonly used composite productive process, and improving interfacial bonding of composites by on-line treatment has always been the focus of attention. In this paper, an on-line ultrasonic treatment system is designed and realized, the resin content of prepregs is determined by the dissolution method; standard deviation and dispersion coefficient are also calculated. The surface morphology, internal structure of prepregs, and the component of resin are observed and analyzed using a Metallurgical Microscope, scanning electron microscope (SEM), and near infrared radiation spectra (NIRS). The strength and performance of prepregs [(tensile strength, bending strength, tensile modulus of elasticity, bending modulus of elasticity, and interlaminar shear strength (ILSS)] are also tested. The results show the on-line ultrasonic treatment system can effectively improve the interfacial bonding of CFRP composites and enhance the strength and performance of CFRP composites.

Influence of electrical discharge machining parameters on cutting parameters of carbon fiber-reinforced plastic

ABSTRACTToday the use of high-strength carbon fiber-reinforced plastics (CFRP) composite as a material for many engineering applications is showing an increasing demand in the industry. These composites are replacing the traditional use of steel because they offer many advantages such as very light weight, high strength, and high stiffness associated with good corrosion-resistant properties. Unfortunately, there is little technological knowledge on the electrical discharge machining (EDM) process of high-strength composite materials, especially about the CFRP. In this work, a study has made into the possibility of using EDM process as a means of machining CFRP composite. Various cutting conditions such as peak current, pulse-on time, pulse-off time and open-circuit voltage were selected to perform electrical discharge machining. The effect of electrode rotation was also studied. Optimum cutting conditions and machine settings for EDM were chosen for machining CFRP composites.

Composite Materials and their Recycling

This paper presents an assessment of the growing use of Glass Fibre Reinforced Plastic and Carbon Fibre Reinforced Plastic composites in the automotive and marine industry through the decades to current use. This report investigates how legislation such as the End of Life of Vehicles (ELV) will force the automotive industry to prepare for end of life recycling and gauge their progress with the aid of reports from the Knowledge Transfer Network (KTN) and Stella Job, who is a Supply Chain and Environment Officer for the UK trade association Composites UK, outlining the process of pyrolysis and solvolysis, with the aid of informal industry interviews and a case study at a small British sports car manufacturer to consider the practical work required.

Fiber Line Optimization in Single Ply for 3D Printed Composites

In conventional manufacturing processes of composites, Carbon Fibre Reinforced Plastic (CFRP) laminates have been made by stacking unidirectional or woven prepreg sheets. Recently, as a manufacturing process of CFRP, 3D printing of CFRP composites has been developed. The 3D printing process of CFRP composites enables us to fabricate CFRP laminates with arbitrary curvilinear fibre plies. This indicates that the optimization of the in-plane curved carbon fibre placement in a planar ply is strongly required to realize superior 3D printed composites. In the present paper, in-plane curved carbon fibre alignment of a ply with an open hole is optimized in terms of maximization of the fracture strength. For the optimization process, a genetic algorithm is adopted. To describe curved carbon fibre alignments in a planar ply, stream lines of perfect flow is employed. By using the stream lines of the perfect flow, number of optimization parameters is significantly reduced. After the optimization, the fracture strength of CFRP laminate is compared with the results of unidirectional CFRP ply. The curved fibre placement in a planar ply shows superior fracture improvement.