Carbon Fiber Reinforced Plastic Research Articles

Investigation of the effect of symmetrical hybrid stacking on drilling machinability of unidirectional CFRP, GFRP and hybrid composites: Drilling tests and damage analysis

Fiber-reinforced plastics are undoubtedly superior to metals in many sectors due to their advantageous properties. Especially carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP) are widely used in industry. Although CFRP offers higher strength, its use is limited due to its high cost. However, with hybridisation, it is possible to produce composites that will provide sufficient strength at lower cost. The mechanical behaviour of hybrid composites may be different compared to glass or carbon composites, as well as the damage behaviour during machining. In this study, the influence of hybrid stacking in drilling hybrid composites was investigated. The results showed the hybrid stacking, especially the position of the carbon plate, has a significant impact on the force generation and damage formation in the drilling. Although stacking the carbon layer at bottom caused an increase in thrust forces, it reduced the damage formation at the hole exit.

Performance-tunable thermal barrier coating for carbon fiber-reinforced plastic composites via flame spraying

Thermal barrier coatings (TBCs) are essential for improving the heat resistance of materials operating in high-temperature environments. This paper proposes a new method for manufacturing double-layered TBC with graded porosity for carbon fiber-reinforced plastic (CFRP) composites. The TBC was created by a flame spraying process, consisting of relatively dense and porous layers: (1) a dense layer was produced by spraying yttria-stabilized zirconia (YSZ) particles directly onto neat carbon fabric substrate and (2) a porous layer was prepared by co-spraying YSZ particles with sacrificial polyetheretherketone (PEEK) particles. The porosity of the porous layer was controlled by varying a PEEK injection distance (D) and a PEEK feed rate (R). The correlation between porosity and thermal conductivity of the TBC layer was investigated to assess its thermal barrier performance. The TBC fabricated with the D = 5 cm and the R = 1.0 g/min offered the optimal porosity and conductivity. The 640μm-thick TBC with 34% porosity and 0.27 W/m·K thermal conductivity protected the CFRP substrate remarkably under the subjected torch at 500°C, as the TBC layer reduced the surface temperature of CFRP to 230°C. Thermomechanical analysis, following thermal shock tests, revealed that the double-layered TBC/CFRP composite retained 87% and 75% of its pristine flexural strength and modulus, respectively, while the neat CFRP composite was completely burnt out. This study explored the application of flame spray technology to develop highly effective double-layered TBCs with tunable porosity to maximize their thermal barrier performances. All results from the current study provide new insights into the design and development of TBC and CFRP composites, which will benefit a wide range of lightweight high-temperature applications.

Copper‐graphene coatings for improving thermal shielding of CFRPs through electrodeposition techniques

AbstractToday, carbon fiber reinforced plastics (CFRPs) are materials of interest several industrial sectors because of their mechanical properties and low weight. However, applications in high‐temperature areas are limited because of thermal degradation. Thus, thin coatings acting as thermal shielding and ensuring the upkeep of CFRP structural stiffness are of high interest. This work presents an innovative approach to produce copper/graphene bilayer coatings through electrodeposition and electrophoretic deposition; it consists of laser pre‐treatment of the composite surface to remove the matrix layer exposing the carbon fibers, enabling the subsequent deposition. Bi‐layer graphene/copper coatings exhibit an enhancement in copper electrodeposition efficiency of more than 59% resulting in a 97% stiffness improvement compared to the single layer copper electroplating. All the obtained coatings were able to act as a thermal shield of the CFRPs, reducing the maximum temperature of the composite by more than 60%. In particular, due to the synergistic effect of copper and graphene, the GNPs‐Cu coating achieved the highest maximum temperature reduction (81%). Cross‐sectional analysis indicates severe delamination in uncoated CFRPs, whereas double‐layer coatings maintain structural integrity and prevent delamination even under high‐energy exposure. In addition, the coated composites exhibit a higher electrical conductivity compared to the laser cleaned CFRP, with the GNPs‐Cu coating that obtained a 90% enhancement because of the outstanding electrical properties of copper and graphene.Highlights The laser cleaning pretreatment allows the electrodepositions on CFRPs. The GNP‐Cu scenario achieves the highest deposition efficiency. A 97% stiffness improvement was achieved by GNPs‐Cu scenario. GNPs‐Cu coatings exhibit the utmost reduction in resistivity (98%). The GNPs‐Cu coating achieves the highest thermal shielding performance (81%).

Ultrasonic welding of continuous carbon fiber reinforced PEEK with embossed energy directors

Ultrasonic plastic welding (UPW) is an efficient and environmentally friendly method for joining carbon fiber reinforced thermoplastic (CFRTP). A crucial aspect of UPW is the design of the energy director (ED). In this study, ultrasonic embossing technology was used to process flat EDs to obtain a new type of ED, named embossed ED. The effect of embossed EDs on the joint formation in ultrasonic welding of continuous carbon fiber reinforced PEEK was investigated in terms of tensile shear properties, macro and micro-morphologies, and fracture morphology. The results show that the use of embossed EDs makes a more homogeneous temperature distribution at the welding interface which significantly reduces defects in the joint. The use of embossed EDs increases the failure load of welded joints by about 50 % (up to 39.6 MPa) and reduces the variation of the joint quality compared with the use of flat EDs. In the optimal condition, the joints made with embossed EDs experiences interlaminar failure of the base material.

Spot-checking machine learning algorithms for tool wear monitoring in automatic drilling operations in CFRP/Ti6Al4V/Al stacks in the aircraft industry

In aircraft manufacturing, where diverse materials, including Carbon Fiber-Reinforced Plastics (CFRP), aluminum, and titanium alloys, are employed, the assembly process heavily relies on creating thousands of holes. These holes accommodate bolts and rivets, facilitating the secure interlocking of structural components within the aircraft fuselage. The proliferation of sensor systems in this domain has led to a substantial increase in data generation during the hole-making process, offering a compelling opportunity to optimize the production system. In this context, this article is dedicated to harnessing the data collected from the production system of a commercial aircraft to refine the assembly process, with a specific focus on reducing consumable costs. The primary approach involves developing a real-time Tool Wear Monitoring System by comparing the performance of Linear Regression, Lasso Regression, Ridge Regression, k-Nearest Neighbors, Support Vector Regression, Decision Tree, Random Forest, and Extreme Gradient Boosting Machine Learning models. Using a scale of the general drill condition as an outcome, the Gradient Boosting Regressor has shown outstanding results. Notably, the residuals consistently exhibited zero-centered errors in training and test sets. However, it suggests that further enhancements are needed to surpass human-level performance in predicting tool conditions because of the quality and quantity of available data.

Adaptive total focusing method for ultrasonic full-matrix imaging of anisotropic CFRP laminates

Abstract The application of total focusing method (TFM) for imaging of Carbon fiber reinforced plastics (CFRP) with ultrasonic phased array is particularly challenging due to the layered structure and anisotropy of CFRP. To improve the TFM imaging performance, the precise knowledge of complex ultrasonic paths in anisotropic CFRP laminates should be obtained for accurate calculation of time of flights (TOFs), which makes the inspection process complicated and time-consuming. In this work, an adaptive TFM is developed for full-matrix imaging of CFRP laminates using ultrasonic phased array. Based on the acquired full matrix data, the elastic constants, including C 11, C 22, C 55, and C 13, can be directly derived using TOFs of A-scan signals. Based on the measured elastic constants, group velocity profiles of quasi-pressure (QP) wave were then calculated for different stacking sequences, from which the TOFs were corrected. To verify the effectiveness of proposed method, simulations and experiments are demonstrated on the CFRP laminates with different stacking sequences. As a representative example, the delamination defects are showcased. Compared with isotropic TFM, the SNR of proposed method is increased by 10.2-18.0 dB. The simulated and experimental results agreed well with each other, indicating that the feasibility of proposed method in full matrix imaging of anisotropic CFRPs.

ScarfingTool: An Advanced tool to repair Carbon Fiber Reinforced plastic

Carbon Fiber Reinforced Plastic (CFRP) is going to assume more and more importance in mechanical and aerospace engineering in the near future. This is due to its intrinsic high lightness and resistance, if compared to traditional metallic materials. CFRP is characterized by a proper production and repair technology. The tool showed in this paper is conceived to repair and verify the restoration of such kind of material. Its application is limited to the first part of the repair process: in jargon the scarfing operation, otherwise called “defect removal”. This operation is similar to a high-speed grinding.For this reason, the designed tool can be easily applied to other contexts, such as sanding, polishing or deburring.Basically, the ScarfingTool is composed by a high-speed electro-spindle and a 3D smart snapshot sensor. This tool is conceived to be as light as possible to be installed on a light collaborative robot. Moreover, its specific design assures great compliance that, as needed, can be regulated. A high efficiency suction inlet completes the tool and guarantees a clean environment during operation. The scarfing process has already been dealt with in [1] to which the interested reader is addressed.This work is licensed under CC BY-SA 4.0. (https://creativecommons.org/licenses/by-sa/4.0)

PA-LCR: A flexible ultrasonic characterization method

Abstract Critically refracted longitudinal (LCR) wave is demonstrated to be prominent in the characterization sensitivity of stress or surface/sub-surface defects. According to Snell’s law, however, its excitation seriously relies on the inclined angle of wedge, i.e., the first critical angle (θ CR). From this, it shows poor adaptability to the variations of wave velocity, especially for elastic anisotropic materials, e.g., carbon fibre reinforced plastic (CFRP) composites. An enhanced strategy based on the phased array ultrasonic, termed PA-LCR, is introduced here. It applies a wide angular distribution of energy to achieve beam steering, and then the beam is targeted at θ CR. LCR wave is successfully excited both in isotropic steel and anisotropic laminate, and the signal-to-noise ratio (SNR) is as high as 19.0-34.6 dB. With the same delay law, the wave can be excited within a wide wave velocity range about 6000 m/s for the steel, and about 3600 m/s for the CFRP laminate, for -6 dB amplitude. The performance of the LCR technique is strengthened by the proposed PA-LCR method.

The impact of various curing methods on the curing process of polymer-fiber composites analyzed using analytical approach

Ti/Gf/Cf represents a novel form of hybrid fiber metal laminates (HFMLs) that successfully blend the benefits of titanium alloy, glass fiber reinforced plastic (GFRP), and carbon fiber reinforced plastic (CFRP). These materials have garnered attention in the field of engineering due to their exceptional levels of stiffness, strength, and shear resistance. The quality of HFMLs during the curing process was significantly impacted by the chosen curing method. Moreover, the use of multiple types of fibers complicated the optimization of curing parameters in HFMLs. A comprehensive study was conducted using a multi-physics field coupling finite element method to investigate the impact of various curing methods on the development of temperature distribution, curing degree, and curing stress in HFMLs during the curing process. By integrating thermal transmission equations, curing kinetics, and viscoelastic mechanical models, a detailed curing simulation model was established. Increasing the cooling rate from 1 °C to 5 °C was shown to raise the maximum curing stress by 4.7 MPa. Additionally, higher curing temperatures were found to induce internal curing stress due to variations in thermal properties. Insufficient insulation times were observed to exacerbate non-uniform temperature distribution and curing degree fields in HFMLs, potentially leading to increased internal stress. To mitigate the generation of large residual stress, it is recommended to lower the heating and cooling rates, reduce curing temperatures, and extend the insulation time appropriately during the curing process of HFMLs. The primary goal of this research was to accurately predict the evolution of curing parameters in HFMLs under different curing regimes, which were impacted by the chosen curing method. The results of the study demonstrated that rapid changes in temperature during heating and cooling stages can lead to uneven curing, resulting in the accumulation of residual stress within the laminates.

Prediction of the Interface Behavior of a Steel/CFRP Hybrid Part Manufactured by Stamping.

Carbon fiber-reinforced plastic (CFRP) is a lightweight material. The automotive industry has focused on producing a steel/CFRP hybrid part to reduce overall weight. After manufacturing, delamination can occur at the interface between the CFRP and steel owing to the hybrid part constituting dissimilar materials. However, most studies have focused only on designing the manufacturing processes for the hybrid part or evaluating the adhesive used at the interface. Therefore, it is necessary to predict the behavior of the interface after demolding the hybrid part. This study aimed to predict the interface behavior of a steel/CFRP hybrid part by considering its forming and cohesive properties. First, double cantilever beam (DCB) and end-notched flexure (ENF) tests were performed to obtain cohesive parameters, such as energy release rate of modes I and II (GI, GII). The experimentally obtained properties were applied to the bonding area of the hybrid part. Subsequently, a forming simulation was performed to obtain the stress of the steel blank in the hybrid part. The stress distribution after forming was utilized as the initial condition for spring-back simulation. Finally, the interface behavior of the hybrid part was predicted by a spring-back simulation. The simulation was conducted using the residual stress of steel outer and the cohesive properties on the interface, without the application of any external forces. The cases of spring-back simulation were divided as delamination occurrence and attached state. The simulation results for prediction of delamination occurrence and bonding showed good agreement in both cases with experimental ones. The proposed method would contribute to expanding the manufacturing of the hybrid part by stamping and reducing the manufacturing cost by prediction of delamination occurrence.

Energy Absorption Behavior of Carbon-Fiber-Reinforced Plastic Honeycombs under Low-Velocity Impact Considering Their Ply Characteristics.

Honeycomb structures made of carbon-fiber-reinforced plastic (CFRP) are increasingly used in the aerospace field due to their excellent energy absorption capability. Attention has been paid to CFRP structures in order to accurately simulate their progressive failure behavior and discuss their ply designability. In this study, the preparation process of a CFRP corrugated sheet (half of the honeycomb structure) and a CFRP honeycomb structure was illustrated. The developed finite element method was verified by a quasi-static test, which was then used to predict the low-velocity impact (LVI) behavior of the CFRP honeycomb, and ultimately, the influence of the ply angle and number on energy absorption was discussed. The results show that the developed finite element method (including the user-defined material subroutine VUMAT) can reproduce the progressive failure behavior of the CFRP corrugated sheet under quasi-static compression and also estimate the LVI behavior. The angle and number of plies of the honeycomb structure have an obvious influence on their energy absorption under LVI. Among them, energy absorption increases with the ply number, but the specific energy absorption is basically constant. The velocity drop ratios for the five different ply angles are 79.12%, 68.49%, 66.88%, 66.86%, and 60.02%, respectively. Therefore, the honeycomb structure with [0/90]s ply angle had the best energy absorption effect. The model proposed in this paper has the potential to significantly reduce experimental expenses, while the research findings can provide valuable technical support for design optimization in aerospace vehicle structures.

Straw Tar Epoxy Resin for Carbon Fiber-Reinforced Plastic: A Review.

The massive consumption of fossil fuels has led to the serious accumulation of carbon dioxide gas in the atmosphere and global warming. Bioconversion technologies that utilize biomass resources to produce chemical products are becoming widely accepted and highly recognized. The world is heavily dependent on petroleum-based products, which may raise serious concerns about future environmental security. Most commercially available epoxy resins (EPs) are synthesized by the condensation of bisphenol A (BPA), which not only affects the human endocrine system and metabolism, but is also costly to produce and environmentally polluting. In some cases, straw tar-based epoxy resins have been recognized as potential alternatives to bisphenol A-based epoxy resins, and are receiving increasing attention due to their important role in overcoming the above problems. Using straw tar and lignin as the main raw materials, phenol derivatives were extracted from the middle tar instead of bisphenol A. Bio-based epoxy resins were prepared by replacing epichlorohydrin with epoxylated lignin to press carbon fiber sheets, which is a kind of bio-based fine chemical product. This paper reviews the research progress of bio-based materials such as lignin modification, straw pyrolysis, lignin epoxidation, phenol derivative extraction, and synthesis of epoxy resin. It improves the performance of carbon fiber-reinforced plastic (CFRP) while taking into account the ecological and environmental protection, so that the epoxy resin is developed in the direction of non-toxic, harmless and high-performance characteristics, and it also provides a new idea for the development of bio-based carbon fibers.

Study of Interlaminar Fracture Toughness and Flexural Properties of Carbon Fibre Composites Reinforced with Polyethersulfone/Graphene Oxide Films

Unidirectional carbon fibre reinforced plastic (CFRP) composites were prepared by inserting polyethersulfone (PES) films or polyethersulfone/graphene oxide (GO) films into the composites and used to improve the interlaminar fracture toughness as well as the flexural properties. The effect of low-temperature cycling (35, 70, 105, and 140 cycles between −55 °C and room temperature (25 °C)) on the flexural properties of the specimens was also investigated, and the damage caused to the reinforcement layer was directly detected by comparing the interlaminar images. The results of the double cantilever beam (DCB) test and the end notched flexure (ENF) test were used to verify the optimisation of the interlaminar fracture toughness and flexural properties of the new composite film (PES/GO film). The results show that the performance of PES/GO film under both DCB test and ENF test is superior to that of PES film. Regarding the effect of low-temperature cycling on the specimens, the flexural properties of the specimens containing PES/GO films were improved. Finally, the matrix interface and failure mechanism of the interlayer reinforcement were investigated by scanning electron microscopy (SEM).

Prediction of low-velocity impact mechanical response and damage in thermoplastic composites considering elastoplastic behavior

By incorporating the plastic deformation and Puck damage criteria law, a three-dimensional elastic-plastic-damage model has been established to predict the behavior of carbon fiber reinforced thermoplastic (CFRTP) composites under low-velocity impacts. The model has been integrated into ABAQUS/Explicit, and off-axis tensile test were conducted to ascertain appropriate parameters for the elastic-plastic model. Additionally, finite element modeling of off-axis tensile were employed to assess the precision of the model parameters and to contrast the variance of accounting for plastic deformation against neglecting it. The effectiveness of the elastic-plastic-damage model, incorporating damage considerations, was confirmed through an analysis of the mechanical response and progressive damage of CFRTP during low-velocity impact tests. Compared to the elastic-damage model that does not consider plastic deformation, the elastic-plastic-damage model, which takes plastic deformation into account, exhibits higher prediction accuracy. Both simulation and experimental results indicate that delamination and matrix cracking are the dominant damage patterns observed in CFRTP at relatively low impact energies (≤16.20 J).

Deep transfer learning for efficient and accurate prediction of composite pressure vessel behaviors

Composite pressure vessels are manufactured by winding carbon fiber-reinforced plastic, while its performance is determined by fabrication conditions. To properly design composite pressure vessels, it is essential to analyze their behavior according to the design parameters. However, analytical or numerical methods have limitations in terms of accuracy or cost-effectiveness. In this study, a method is proposed to accurately and efficiently predict the behavior of composite pressure vessels through deep transfer learning. A prediction model is built by pre-training on a sufficient amount of analytical data, and then fine-tuning on a limited amount of numerical data. The performance of the deep transfer learning-based prediction model was evaluated through various error assessments. Its computational cost was also compared with that of finite element analysis. Furthermore, the deep transfer learning-based prediction model was used to analyze the impact of design parameters on the behavior of composite pressure vessels and for design optimization.

Buckling behavior analysis of corrugation reinforced composite pressure shell: Analysis of the influence of corrugation structural parameters

Based on CFRP(Carbon Fiber Reinforced Plastics) cylindrical pressure shell, the CFRP circumferential corrugation pressure shell is proposed in this study. The structure can further improve the buckling resistance capacity of CFRP pressure shell. Five CFRP circumferential corrugation pressure shells with varying corrugation structure parameters are designed and compared with CFRP cylindrical pressure shell. The buckling behaviors of the shells are analyzed in detail by nonlinear finite element method. The result show that reasonable corrugation structure can significantly improve the resist buckling capacity of CFRP cylindrical pressure shell. However, the increase of corrugation structure parameters will exacerbate the damage to the CFRP layers outside the pressure shell. Ultimately, pressure shell N2 with the best buckling resistance capacity is selected for hydrostatic pressure test, and the experimental results are found to align with the numerical simulation results. This study offers a novel approach for the design of deep-sea pressure shell structures.

Comparative study of dielectric characteristics and radio transparency of composite materials

Polymer composites with low dielectric properties and excellent radio transparency are essential for high signal transmission rates and high device integration. However, creating dielectric polymer composites with high radio transparency is a challenging task. This work presents comparative results of studying the dielectric loss, permittivity and radio transparency of composite materials, such as aramid-epoxy composite (AEC), glass fiber (GF), carbon fiber reinforced plastic (CFRP), and ultra-high molecular weight high-density polyethylene (UHMWPE). Based on the experimental results, the following transmission percentages were established for various materials: CFRP – 2.45%, AEC – 79.43%, UHMWPE – 80.16%, and GF – 78.88%. The dielectric loss tangent angle of carbon fiber is significantly higher compared to other polymer composites, UHMWPE exhibits the lowest tangent angle values, and AEC and GF have stable and low dielectric loss. The obtained polymer composites demonstrated low dielectric permittivity values: AEС 2.9, UHMWPE 2.56, and GF 3.64.

Surface physics and chemistry of carbon fibers enhance dissimilar sheet joining of carbon fiber-reinforced plastic by copper electrodeposition

Carbon fiber-reinforced plastic (CFRP) sheets were dissimilarly edge-joined with anodized A6061 Al alloy sheets by copper electrodeposition. A high bonding strength of 137 MPa was attained following a series of pretreatments including etching in KMnO4 + NaOH hot aqueous solution, anodization at 2 V vs. SUS316 cathode in 1 mol L˗1 H2SO4, and sulfonation in hot concentrated H2SO4. The anodization physically cleaned the carbon fiber (CF) surface in CFRP. The chemical surface properties of the CFs were modified by the anodization, introducing crystallographic defects and CO groups. This physical and chemical modification of CFs in CFRP resulted in good adhesion of the electrodeposited copper.

Defect monitoring method for Al-CFRTP UFSW based on BWO–VMD–HHT and ResNet

Underwater friction stir welding (UFSW) achieves reliable joining between dissimilar materials and meets the welding demand for function and properties in lightweight structures of modern engineering. A defect monitoring method based on Variational Mode Decomposition optimized by Beluga Whale Optimization and Hilbert–Huang Transform (BWO–VMD–HHT) is proposed to solve the unclear feature of AE signal in UFSW due to the aqueous medium. UFSW experiments on Al alloy and carbon fiber reinforced thermoplastic (CFRTP) are carried out with AE signals measured. The time–frequency domain features of AE signals are extracted by BWO–VMD–HHT. The experimental results show that the main frequency of the AE signal is 22.5 kHz, and surface crack defects, shallow hole defects, and deep hole defects are accompanied by the transfer phenomena of different frequency components. Then, the feature vectors are built by frequency components in the BWO–VMD–HHT spectrum and reduced by principal component analysis, including 22.5 kHz, 24 kHz, 20.6 kHz, 18.4 kHz, 17.3 kHz, and 15.6 kHz. The feature vectors are divided into the train and test sets, and the welding defect prediction model (ResNet18-attention) is built by ResNet18 and trained by feature vectors. In the test set, the ResNet18-attention is compared with the BP, SVM, and RBF. Test results show that the precision of models has improved by at least 10%, which are trained by BWO–VMD–HHT features vector. Also, ResNet18-attention has achieved an average precision of 0.906 and recognizes the category of weld defect accurately, and this method can be applied to the defect monitoring of UFSW.

Curing kinetics and mechanical properties of the epoxy vitrimer based on transesterification and its composite laminates

AbstractThe resin is a fundamental factor in determining the performance and usage conditions of its composites. The epoxy vitrimer, which combines both thermoplastic and thermosetting properties, shows significant potential in extending the service life of material. The curing process significantly affects the macroscopic properties of the vitrimer and the resulting carbon fiber reinforced plastics (CFRP). Effective control of curing parameters constitutes the critical factor for the assurance of product quality. In the study, a differential scanning calorimetry (DSC) was utilized to establish a curing kinetics model for a modified, self‐healable epoxy vitrimer based on transesterification. Then the molecular structure, thermodynamic, and mechanical properties of the cured vitrimer were analyzed. Next vitrimeric CFRP (vCFRP) laminates were fabricated, and the tensile and bending properties of the vCFRP laminates were investigated. The results showed the curing process was obtained: 95°C/1 h + 150°C/2 h + 170°C/2 h. The thermodynamic and mechanical properties of cured vitrimer could meet practical requirements. The minimal differences observed in the stress–strain curves of the specimens indicated that the curing process was appropriately configured. The prepared laminates exhibited performance comparable to that of commercial thermosetting composites.