Strength Of Carbon Fiber Reinforced Plastics Research Articles

Effect of nano-silica modified resin on the interface strength and toughness of Al/CFRP hybrid laminates

In order to improve the interfacial strength and toughness of aluminum alloys and CFRP (carbon fiber reinforced plastics) hybrid laminates, modified resin with lower porosity was prepared by adding nano silica treated with silane coupling agent into epoxy resin. Al/CFRP hybrid laminates with modified resin were prepared by physical liquid deposition method and hot-press process. The strength and toughness of Al/CFRP hybrid laminates with modified resin were evaluated by tensile shear test and end notch fracture (ENF) test. The experimental results showed that the interfacial shear strength of Al/CFRP hybrid modified resin laminates is 18.8±0.8MPa and the fracture energy is 1546.33±10.26 J /m2, which is 28.76% and 15.38% higher than that of Al/CFRP hybrid laminates with raw resin, respectively. The well-dispersed silicon nanoparticles effectively mitigate internal stress during the cross-linking process of the modified resin, thereby diminishing the dimensions of microcracks within the modified resin. The transition layer of the modified resin interface formed a cooperative and smooth structure. This structure can ensure that the transition of elements in the interface layer is smooth, and it is not easy to cause stress concentration. The formation of new bonds (C-Si bonds) at the interface of the modified resin indicates an enhancement of bonding strength at the interface, superimposing upon van der Waals forces, thereby enhancing the adhesive strength of the modified resin interface.

Study of the effect of combined reinforcement and modification of epoxy resin with rubbers on the impact strength of carbon fiber-reinforced plastic

Study of the effect of combined reinforcement and modification of epoxy resin with rubbers on the impact strength of carbon fiber-reinforced plastic

Enhanced Estimation of Axial Compressive Strength for CFRP Based on Microscale Numerical Simulation and the Response Surface Method.

Compressive strength is one of the most important properties of carbon fiber reinforced plastics (CFRP). In this study, a new method for predicting the axial compressive strength of CFRP using the response surface method is developed. We focused on a microbuckling model to predict the compressive strength of unidirectional fiber composites. For the microbuckling model, axial shear properties are required. To obtain the compressive strength for various material properties, we perform individual shear tests and numerical simulations, but these require enormous computational costs and extended time. To address the issue of computational cost, in this study, we propose a new method to predict compressive strength using the response surface method. First, we perform shear simulation in a microscale fracture model for unidirectional CFRP with various parameters of the fiber and resin properties. Based on the results of the shear simulation, the response surface method is used to evaluate and develop prediction equations for the shear properties. This method allows for the study of the objective values of the parameters, without significant computational effort. By comparing both the results predicted from the response surface method (RSM) and the simulation results, we verify the reliability of the prediction equation. As a result, the coefficient of determination was higher than 94%, and the validity of the prediction method for the compressive strength of CFRP using the response surface method (RSM) developed in this study was confirmed. Additionally, we discuss the material properties that affect the compressive strength of composites comprised of fibers and resin. As a result, we rank the parameters as follows: fiber content, elastic modulus after resin yield, yield stress, and initial elastic modulus.

Functional-gradient carbon fiber-reinforced plastic based on epoxy matrix modified with thermoplastic elastoplast

Modification of epoxy binders with butadiene-styrene thermoplastic elastomers was used to obtain functional-gradient carbon plastics with increased impact resistance. Samples were made and comparative tests of carbon fiber-reinforced plastics for resistance to impact loads and compression after impact were carried out. It is shown that smooth change of modifier concentration at transition from the external surface of the part to the internal one allows to increase effectively the impact strength of carbon fiber-reinforced plastic while maintaining the rigidity of the composite material.

Simultaneous Optimization of Carbon Fiber Allocation and Orientation by IFM-GA

This paper proposes an individual fitness method genetic algorithm (IFM-GA) for carbon fiber-reinforced plastic (CFRP). The strength of CFRP depends on the carbon fiber allocation and orientation. Waste carbon fiber is generated if this design is inappropriate. Consequently, CFRPs are less cost-effective. It is necessary to optimize the allocation and orientation as design variables to solve this problem. The problem involves combinatorial optimization. The genetic algorithm (GA) is suitable for combinatorial optimization. However, it is difficult to obtain an optimal solution using the GA owing to the large number of combinations. Hence, the IFM-GA is developed in this study. It is a GA-based method with a different fitness calculation. The GA calculates the fitness of each design, whereas the IFM-GA calculates the fitness of each design element. As a result, the IFM-GA yields a higher-stiffness design than the GA. To conclude, the IFM-GA can enable optimum fiber allocation and orientation, whereas the GA cannot.

Analysis of the efficiency of advanced methods of in-plane shear testing of highstrength CFRP specimens

The mechanical testing performed to determine shear characteristics of advanced carbon fiber-reinforced plastics (CFRP) can involve significant problems. First of all, this is due to the difficulties in providing uniform distribution of shear stresses in the working area of the specimens, particularly in determining the strength characteristics of advanced polymer composite materials based on high-modulus or highstrength carbon fibers with the ± 45° layup, where the material properties depend not only on the matrix but also on the fiber properties, unlike unidirectional composites. In addition, one can mention a large number of shear test methods and related standards of in-plane shear testing. At the same time, the results of the tests performed according to various standards generally do not comply with each other. In this study the analysis of CFRP shear characteristics obtained from various test methods was performed. The calculated and experimental data of stress-strain distribution for various specimen types were obtained. The experimental results of determining the strength and elastic characteristics of CFRP in the in-plane shear were obtained during the testing of 125 flat specimens made of four brands of CFRP reinforced with the ± 45° plies. None of the standard methods discussed in this study was found to provide uniform distribution of shear stresses in the working area of the test specimen. The strength values closest to the predicted ones were obtained from the specimens made according to ASTM D7078 (GOST R 57207) based on the method of V-notch plate distortion. At the same time, the method of plate distortion in the four-bar linkage (GOST 24778, ASTM D2719) and the losipescu method (ASTM D5379, GOST R 56799) cannot definitely be used to reliably determine the shear strength characteristics of advanced CFRP reinforced with the ± 45° plies.

Structural lightweight components for energy-efficient rail vehicles using high performance composite materials

The structural application of carbon fiber reinforced plastic (CFRP) in rail vehicles allows significant mass reductions compared to classic metals due to the outstanding specific stiffness and strength of CFRP. However, for CFRP materials in rail vehicle technology as a quite new field of application, various challenges must be overcome, such as the development of suited design approaches for main load-bearing train parts considering all rail specific standards. In this paper the development of related design approaches is exemplary shown for a bogie frame and a pantograph platform. The achieved mass reduction is almost 50% for the bogie frame and 40% for the pantograph platform compared to the metallic reference systems. Both CFRP lightweight structures have been successfully tested under static and fatigue loading according to valid railway standards.

Bond Strength Properties of GFRP and CFRP according to Concrete Strength

Reinforced concrete is the most commonly used material in the construction industry. However, one disadvantage of reinforced concrete is that environmental factors cause materials to penetrate the concrete and cause steel bar corrosion. Rebar corrosion increases its volume significantly by approximately 3–6 times, which lowers concrete–rebar adhesion. This severely affects the serviceability and durability of concrete structures. The economic and social impacts of such deterioration are extremely large. To reduce corrosion, glass fiber-reinforced plastics (GFRP) and carbon fiber-reinforced plastics (CFRP) can be applied to concrete. The rebar–concrete bond strength is an important factor to be considered while applying GFRP and CFRP. Thus, we experimentally investigated the adhesion strength of GFRP and CFRP in relation to the strength of concrete and water–cement ratio according to ASTM C 234 to correlate the data for the development of GFRP and CFRP as substitutes for deformed reinforcing bars. The results showed that a lower water–cement ratio yielded higher compressive strength and bond strength; the bond strength of GFRP was approximately 23% lower than that of CFRP. The coating of the rebar surface required for GFRP and CFRP application in reinforced concrete structures ought to be investigated in the future.

Indirect buffer-based laser pretreatment method for enhancing the adhesive bonding of carbon fiber-reinforced plastic

The bonding technology of carbon fiber-reinforced plastic (CFRP) is a key technology in its production. Laser pretreatment is a common method for improving the bonding strength. However, the use of laser pretreatment without damaging the carbon fibers has always been challenging. A laser pretreatment method is proposed to improve the bond strength of CFRP without damaging the carbon fibers. The proposed method increases the tensile shear strength of CFRP from 2448 to 4851 N; 9.79 to 19.41 MPa. The naked carbon fiber treated by buffer laser pretreatment provides additional strength to the glue. Scanning electron microscopy was used to image the surfaces of the samples. Failure modes were also investigated to explain the increase in bond strength. The benefits of this method can be explained using a thermal model, and this method can be used as a reference for the laser processing of CFRPs.

Influence of stirrup ratio on size effect of shear strength of concrete beam-column joints reinforced with CFRP bars

<p indent="0mm">The shear failure behavior and the size effect of shear strength of carbon fiber-reinforced plastic (CFRP)-reinforced concrete beam-column joints are investigated in this study. The finite element model for failure analysis of CFRP-reinforced concrete beam-column joints was established using a mesoscale numerical method. The mesoscale failure mode and failure mechanism of geometrically similar CFRP-reinforced concrete beam-column joints were studied, and the influence of CFRP-bar ratio on shear strength and size effect law of joints was discussed. The simulation results show that the nominal shear strength of CFRP-reinforced concrete beam-column joints has an obvious size effect, and the size effect of shear strength can be alleviated by increasing the CFRP-bar ratio. In addition, it is found that the size effect of the nominal shear strength of concrete beam-column joints with CFRP bars is more obvious than that of reinforced concrete (RC) beam-column joints. Based on the size effect law of nominal shear strength for RC beam-column joints, considering the effect of stirrup ratio proposed in the previous work, along with the numerical test results in this study, the size effect law was extended and established for the analysis of nominal shear strength of concrete beam-column joints with CFRP bars.

Optimization of Carbon Fiber Reinforced Plastic Curing Parameters for Aerospace Application

The use of carbon fiber reinforced plastic (CFRP) is increasing in engineering applications such as aerospace, automobiles, defense, and construction. Excellent strength-to-weight ratio, high impact toughness, and corrosion resistance make CFRP highly suitable for aerospace applications. Curing temperature, curing time, and autoclave pressure are among the most important curing parameters affecting the properties of CFRP. Tensile strength, impact toughness, and hardness of CFRP were selected as desirable properties for optimization. A 23 full factorial design of experiment (DOE) was employed by varying curing temperature (120 and 140 °C), curing time (90 and 120 min), and autoclave pressure (3 and 7 bar) while keeping the number of experiments to a minimum level. The cured samples were subjected to tensile strength, impact toughness, and hardness tests at room temperature as per relevant ASTM standards. Analysis of variance (ANOVA) was used, and it was found that tensile strength, impact toughness, and hardness were influenced most significantly by temperature and time. The maximum tensile strength and hardness were achieved for curing cycle parameters of 140 °C, 120 min, and 7 bar, and impact toughness was maximized for 140 °C, 120 min, and 3 bar. A concept of composite desirability function was used to achieve simultaneous optimization of conflicting tensile strength and impact toughness properties for the specific application of aircraft skin.

Optimization of HNT nanoparticle distribution based on EPD process in epoxy–CFRP composites

There are numerous methods for reinforcing laminate composites using nanoadditives. However, the random dispersion of nanoparticles in polymer resins leads to critical defects owing to excessive dispersion. This study investigated a method of depositing halloysite nanotubes (HNTs) on a carbon fabric surface via electrophoresis deposition (EPD) for reinforcing the through-thickness strength of carbon fiber-reinforced plastic (CFRP) composites. The voltage during the EPD process was set as 6–12 V, which is the working range for nanoparticles during EPD. In addition, CFRPs were fabricated from modified carbon fabrics using vacuum-assisted resin transfer molding. The optimum voltage was determined as 6 V. At higher voltages, the mechanical properties deteriorated owing to the distribution of HNTs and damage to the fibers. The performance of the EPD-modified CFRPs was better than that of neat CFRPs. The highest strength was observed at 0.7 wt.% HNTs and 6 V, which indicated the feasibility of the EPD process and a well-dispersed morphology. The strong interaction of HNTs with carbon fabric influences the through-thickness mechanical properties of CFRP composites.

Influencing Factors on the Longitudinal Compression Properties of Pultruded Unidirectional Fiber Composites

Unidirectional fiber composites produced by pultrusion have good mechanical properties. We conducted compression experiments to investigate the factors that influenced the compression of pultruded unidirectional carbon fiber-reinforced plastics (CFRPs) under static axial loads. The CFRPS were composed of carbon fiber or carbon fiber cloth as reinforcement material, resin, ceramic, metal, cement, carbon or rubber as matrix. The modulus and compressive strength were measured. The experimental data were compared with the theoretical values obtained from the rule of mixtures. Moreover, the effects of the components, dispersion, interface states, and other factors on the compressive mechanical behaviors of the composites were studied. Scanning electron microscopy revealed the microstructure and fracture of the material. The results showed that the modulus and compressive strength of the CFRPs with a higher carbon fiber modulus decreased with the modulus and resin strength. The compressive modulus and compressive strength of CFRPs with the same resin increased with the modulus and strength of the carbon fibers. Upon increasing the modulus and strength of the carbon fibers, the compressive modulus and compressive strength of the CFRPs decreased with the modulus and strength of the resin. Moreover, glass fiber-reinforced plastics (GFRPs) were used to compare the difference between CFRPs, C/GFRP, and GFRP. The relationship between the the microstructure and promperties of these composites was systematically revealed. These research results are valuable for the design and synthesis of low-cost pultruded unidirectional fiber composites with excellent mechanical properties.

Development of Unidirectional CFRP Reinforced Aluminum Bumper Reinforcement

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Since bumper reinforcements are positioned at front/rear ends of vehicles, weight reduction of the bumper reinforcements enhances vehicle dynamic performance by reducing a yaw moment of inertia. CFRP (Carbon Fiber Reinforced Plastic) composites are attractive lightweight materials due to their excellent specific strength and rigidity. However, because of their relatively high cost, applications of CFRP materials to vehicle structural parts are limited. In this study we have developed a lightweight, structural part, which consists of a thin-walled Al (Aluminum) bumper reinforcement with a UD (Unidirectional)-CFRP sheet. The intention is to prevent an increased part cost by reducing the amount of Al and by minimizing the amount of CFRP. Compared to Al, UD-CFRP sheets have even higher tensile strength and modulus. When vehicles crash, bumper reinforcements may be subjected to bending force. If a UD-CFRP sheet is adhered on the tensile side of an Al bumper reinforcement, not only Al thickness on the tensile side, but also thickness on the compression side can be reduced due to movement of the bending neutral axis. In this design with a multi-material structure, bending strength of the developed part can’t be predicted by a full plastic moment which could normally be used to predict metal parts’ bending strength under large deformation. We employed a novel cross-section design method which can be used to predict bending strength of CFRP reinforced metal structures under large deformation. To validate the calculation method, three-point bending tests on the parts were carried out. Experimental data of bending strength were in the range of predicted bounds. Also, in order to launch the developed part, robustness of part’s performance was evaluated. Finally, the part was adapted to the rear bumper reinforcement of LEXUS RC-F. The part weight is 11 % lighter compared to the conventional, all-Al, bumper reinforcement.&lt;/div&gt;&lt;/div&gt;

Fatigue Life Prediction for Carbon-SMC and Carbon-FRP by Considering Elastic Modulus Degradation

In the automotive industry, being lightweight has become an important design factor with the enhancement of environmental regulations. As a result, many studies on the application of composite materials are in progress. Among them, interest in carbon materials, such as carbon sheet molding compound (C-SMC) and carbon-fiber-reinforced plastic (CFRP), which have excellent strength and stiffness, is increasing. However, CFRP is a material that makes it difficult to secure economic feasibility due to its relatively high manufacturing costs and limited mass production, despite its excellent mechanical strength and durability. As a result, many studies have been conducted on C-SMC as an alternative carbon composite material that can be easily mass-produced. In this regard, this study intended to conduct a study on evaluating the fatigue strength of C-SMC and CFRP among mechanical properties due to the lack of clear failure criteria for fatigue design. We investigated the tensile and fatigue strengths of C-SMC and CFRP, respectively. In the case of C-SMC, the mechanical strength tests were conducted for two different width conditions to evaluate the cutting effect and the machining methods to assess the effects of the edge conditions. To evaluate the fatigue failure assessment criteria, the stiffness drop and elastic modulus degradation criteria were applied for each fatigue test result from the C-SMC and CFRP. The results confirmed that the rationality of the failure criteria in terms of the stiffness drop and the application of the fatigue life prediction of C-SMC based on elastic modulus degradation demonstrated promising results.

Tensile strength of CFRP with curvilinearly arranged carbon fiber along the principal stress direction fabricated by the electrodeposition resin molding

To strengthen carbon fiber reinforced plastics (CFRPs), fiber placement along the principal stress directions have been studied as a promising approach. However, a method to sufficiently impregnate a resin between the curved carbon fibers has not established thus far, although arbitrary arrangement of carbon fibers is feasible using the automated fiber placement (AFP) machine. Previously, the authors had developed an electrodeposition resin molding method based on electrophoresis. In this method, the carbon fiber preforms sewn by the AFP machine is immersed in the electrodeposition solution containing polymers with epoxy groups, and optimal current is applied to impregnate resin between carbon fibers. In this study, we showed that a CFRP specimen could be fabricated with arranging the carbon fibers along the principal stress direction, resulting in approximately 10% higher tensile strength than that of the specimen with unidirectional carbon fibers.

Effect of Plasma Treatment of a Carbon Tape before the Deposition of a Metallic Coating onto It

The adhesion of a metallic coating to a carbon tape after its treatment with cold plasma under various conditions is experimentally studied, and the optimum conditions are selected. Plasma treatment is found to increase the adhesion strength estimated by adhesive tape testing by several times. A metallic coating is deposited onto a carbon tape after plasma treatment by magnetron sputtering. A carbon tape with a metallic coating is used to fabricate carbon-fiber reinforced plastics (CFRPs) with an epoxy binder, and the plastics are molded using vacuum infusion. A metallic coating made of stainless steel on a carbon tape is found to increase the interlayer shear strength of CFRPs by 40%; a titanium coating, by 30%; and a copper coating, by 13%.

Enhancement of the mechanical properties of the CFRP by cellulose nanofiber sheets using the electro-activated deposition resin molding method

Cellulose nanofibers (CNFs) have high strength. Therefore, many studies have been conducted to improve the mechanical properties of carbon fiber reinforced plastics (CFRP) by dispersing CNF in the matrix. However, since CNFs are hydrophilic, a hydrophobic treatment is required. Previously, authors showed the bending strength of CFRP could be enhanced by CNFs without a hydrophobic treatment. Applying the electro-activated deposition resin molding (ERM) method to fabricate CFRP, CNFs can be applied on the surface since the electro-activated deposition solution is essentially water-based and contains a polymer with epoxy groups. In this study, the CNF sheet was prepared by drying CNF dispersion in advance. Shortly after the ERM, the CNF sheet was applied to the surface of the CFRP. The mechanical properties of the CFRP were enhanced, the maximum elastic modulus and tensile strength were 2.3 times and 1.7 times of the CFRP specimen without the CNF sheet, respectively.

Polyaniline-based all-polymeric adhesive layer: An effective lightning strike protection technology for high residual mechanical strength of CFRPs

Carbon fiber reinforced plastics (CFRPs) are vulnerable to lightning strikes due to their low electrical conductivity and low heat resistance. A lightning strike can damage CFRP structure catastrophically. Most common lightning strike protection (LSP) technology, consists of expanded metal foils/films on top of composite structures. This technology possesses disadvantages such as increased weight, galvanic corrosion, expensive integration and repair costs. In the present study, authors introduce a novel, easy to apply and all-polymeric LSP material. A doped intrinsic conductive polymer i.e. Polyaniline (PANI) dispersed in a thermosetting cross-linking polymer divinylbenzene (DVB) has been used to prepare an adhesive layer of 0.25–0.4 mm thickness. CFRP structure coated with PANI-based LSP layer, when tested against simulated lightning impulse current of 100 kA, demonstrated effective dissipation of the current, rendering almost 100% safety to the CFRP structure. PANI showed the capability to create a 3-D conductive network due to its self-assembling property, which makes it superior compared to its counterpart carbon/metal nano-filler based LSP technologies. Almost 100% residual strength of PANI-LSP protected CFRPs is reported in this work.

Bending fracture rule for 3D-printed curved continuous-fiber composite

Three-dimensional (3D) printing is an attractive technology to produce complex structures without the need for expensive tools and molds. Additives are usually incorporated with the plastic materials used in 3D printing to increase their strength and rigidity. In particular, carbon fiber-reinforced plastic (CFRP) shows promise as a material for use in 3D printing. However, the strength of CFRP after printing is still unclear, although it is known that its strength is affected by the plastic melting during printing. In this study, we analyzed the fracture behavior of CFRP specimens before and after bending to different curvature radii. From the experimental results, a fracture criterion that described the behavior of the materials by considering tensile and compressive loads was developed. The fracture mechanism was the same for CFRP specimens with different curvature radii. These results increase our understanding of the mechanical properties of CFRP materials used in 3D printing.