Mechanical Properties Of Carbon Fiber Reinforced Plastics Research Articles

Effect of marine environment on the mechanical properties degradation and long-term creep failure of CFRP

The carbon fiber reinforced plastics (CFRP) has broad application prospect in the marine field, but its significate long-term performance and failure mechanism are still unclear. In this paper, the mechanical property degradation and creep failure mechanism of CFRP in marine environment were investigated by the molecular dynamics (MD) method. Based on the CFRP molecular model established in dry, pure water and salt immersion environment, the effect of service conditions on it in marine environment was explored. The results show that the marine environment can lead to a significant decrease in the mechanical properties of CFRP only in the vertical fiber direction, and the degradation extent increases with the increase of temperature. The effects of pure water immersion and salt immersion environment on its mechanical properties are basically the same. High stress level, hygrothermal environment and high temperature salt immersion environment will accelerate the creep failure of CFRP. Later, the creep failure mechanism of CFRP is analyzed from microstructure and microscopic energy. Microstructure analysis shows that water molecules could accelerate the movement of epoxy fragments and lead to CFRP failure. Microscopic energy analysis shows that the conversion process of strain energy and the decline of interface performance are the important reasons for creep failure. The finds of this paper introduce a new method to study the long-term performance of CFRP and can provide reference for the engineering application of CFRP in marine environment.

Effect of Matrix Resin Characteristics on the Fracture Behavior for Plain-Woven Carbon Fiber Reinforced Plastics fabricated by Vacuum Assisted Resin Transfer Molding

Acoustic emission (AE) measurement has been used to investigate microscopic failures and damage progress in carbon fiber reinforced plastics (CFRP). In this work, AE measurements were conducted on plain-woven CFRPs fabricated by vacuum-assisted resin transfer molding process and neat epoxy resins during tensile tests to evaluate the failure modes. Four types of epoxy resins were used as matrix resins to investigate the effects of matrix resin characteristics on the microscopic damage behavior and the mechanical properties of CFRP. As a result, the mechanical properties of on-axis CFRP were comparable regardless of matrix resins. On the other hand, in the case of off-axis CFRP, such as 45° direction, the tensile strength was remarkably lower with a brittle matrix resin. From the AE measurement results, the number of cumulative hits for CFRP was much larger than that for neat resins due to the occurrence of fiber/matrix interfacial cracks. Also, AE waves for CFRP had a longer duration than that for neat resin, and the relationship between the degree of duration and fracture mode was clarified.

Microstructure variations in carbon fiber reinforced plastics under ultraviolet-ray irradiation

Carbon fiber reinforced plastics (CFRPs) were irradiated with ultraviolet rays (UVR), and its structural variations were observed by high-resolution transmission electron microscopy. The lattice images of the resin, fibers, and fiber/resin interface regions in CFRPs and their spatial frequencies were investigated before and after UVR irradiation. In the fiber regions, the layer spacing of graphite structures increased after UVR irradiation. In the fiber/resin interface regions, the resin and the fiber adhered tightly at the atomic level before UVR irradiation. The anisotropic interface phases, in which atom-pairs having wide spacings were aligned along the direction perpendicular to the interface planes, were formed. After UVR irradiation, the tight interface adhesion was maintained, whereas the roughness of the interface shape increased. The effects of UVR irradiation on the mechanical properties of CFRPs were revealed from the atomistic structural variations in the resin, the fibers, and the fiber/resin interfaces.

Preparation and Mechanical Properties Analysis of Aviation Mechanical Carbon Fiber Reinforced Plastics

The study aims to explore the preparation of aviation mechanical carbon fiber reinforced plastics (CFRP) and the properties of CFRP composites. Taking the aero box body as an example, the mechanical properties of CFRP are studied. The preparation of CFRP is analyzed by searching the data. CFRP plates are explored according to the stress analysis of composite materials. The finite element analysis software ANSYS Workbench and UG software are adopted to build the 3D model of the aero box body. After adding materials in ANSYS Workbench and simplifying the UG model, the finite element analysis of the model is carried out by computer. The 3D model of the aero box is constructed, the finite element analysis of the aero box is carried out, and the mechanical properties of CFRP are explored. In this study, the possibility of the practical application of CFRP in the aviation box body lightweight is clarified, which gives a direction for the subsequent actual molding and guides the application of CFRP in aviation field.

Influence of defined amount of voids on the mechanical properties of carbon fiber‐reinforced plastics

The fault‐free fabrication of fiber‐reinforced plastics (FRPs) is a big hurdle for textile and composite manufacturers. Voids are generated during the infiltration process of FRPs, which then reduce the mechanical performance of FRPs. This paper describes the effect of defined amount of voids on the mechanical properties, such as tensile, bending, impact and inter‐laminar shear strength of FRPs. The defined amount of voids in carbon FRPs are produced by a newly developed process—mixing of a foaming agent with resin system during the infusion process. The utmost advantage of this process is simple, time‐saving and reproducible. The produced FRPs from this process can be utilized for the validation of ultrasonic testing of FRPs. Four types of FRPs with six carbon layers are fabricated by a vacuum assisted resin infusion process. Carbon fibers are chosen in this study because of their growing market potential. Then, the mechanical properties of the produced carbon FRPs are tested. Besides the mechanical testing, the microscopic testing and ultrasound testing is executed to qualitatively analyze the length and distribution of produced voids. Results reveal that the mechanical properties of carbon FRPs reduce by an increase in defined amount of voids. POLYM. COMPOS., 40:E1049–E1056, 2019. © 2018 Society of Plastics Engineers

Topologically optimized shape of CFRP front lower control ARM

This study shows topology optimization of lower control arm (LCA), made of carbon fiber reinforced plastic (CFRP), that was originally composed of aluminum alloy. By mean-field homogenization (MFH) method, averaged mechanical properties of CFRP are applied to FEM analyses of 3D LCA model. The design target is to reduce the LCA weight while satisfying the multiple constraints including required stiffness and durability conditions at the same time. As a result, authors propose the new design of CFRP LCA with 30 % weight reduction compared to Al alloy LCA.

Accelerated thermo-oxidative aging for carbon fiber reinforced polycyanate under high pressure atmosphere

The aim of this study is to accelerate thermo-oxidative aging in carbon fiber reinforced plastics (CFRP) submitted to high temperature atmospheric pressure. In this study, long-term thermo-oxidative aging test was conducted to examine the effect of high pressure atmospheric environment on the weight and mechanical properties of CFRP to accelerate the rate of thermo-oxidative degradation. The effect of thermo-oxidative environment under high atmospheric pressure on the change in weight, strength, and shrinkage behavior of a CFRP with polycyanate (FSD-M-08178) was investigated. The aging test was conducted at 180 °C up to 8,000 h under atmospheric pressure and the test result was used as a reference data. Other aging tests were also conducted under elevated pressure conditions (0.3 and 0.5 MPa) at the same exposure temperature up to 2,000 h and the test results were treated as the accelerated aging test data. Unidirectional laminates [0]8 and [90]8 for tensile specimens and angle ply laminates [±45]2S for off-axis tensile specimens were aged in oven, and then mechanical tests were carried out on them. The results indicated that elevated pressure would cause faster and larger weight gain in earlier aging period. The outcomes of these experiments were changes in weight, strength, and local shrinkage deformation were changed quickly under elevated atmospheric pressure environment. Same micro damage onset and extension irrespective of pressure during thermo-oxidative aging and subsequent loading test were observed. The test results indicate that the change in weight, strength, and local shrinkage deformation could be accelerated by elevated pressure without change in thermo-oxidative degradation mechanism. Therefore, the elevated pressure testing would be a better method to accelerate thermo-oxidative degradation. On the other hand, the change in strength under elevated pressure conditions is faster than local shrinkage deformation. Equivalent acceleration rate of degradation could not be obtained.

Computerized Testing Machines to Study the Effect of Strain Rate on Mechanical Properties of CFRP

In this paper, a universal testing machine and animpact testing apparatus have been upgraded by using a high accuracy data acquisition and control system interfaced to apersonal computer with proper sensors and actuators. Thepurpose of the upgrade is to increase the accuracy of themeasurements and to perform advanced material testingprocedures that are not possible with the old configuration.The modernization process not only permits the accurate dataacquisition and convenient operation but also the ability tostudy the effect of strain rate on the tensile properties ofmaterials. Also, an experimental study of the response of CFRP(Carbon Fiber Reinforced Plastic) material to low andintermediate strain rates has been carried out.

Influence of Different Modeling Strategies for CFRP on Finite Element Simulation Results

Numerical simulation is used to predict the behavior and response of carbon fiber reinforced plastic (CFRP). Sometimes zero thickness of interface layer is introduced into the numerical model to investigate the inter-layer behavior like delamination. To investigate the influence of critical volume-type defect like void, usually appeared in matrix rich region at the interface between layers, on mechanical properties of CFRP, numerical models with different interface thickness were created and tensile property and three-point bending simulation results were compared to experimental ones. It is found that accurate result is obtained with increasing of the interface thickness and up to 20% that of layer thickness is recommended to model the matrix rich region.

Effect of plasma surface treatment of recycled carbon fiber on carbon fiber-reinforced plastics (CFRP) interfacial properties

We studied the effects of plasma surface treatment of recycled carbon fiber on adhesion of the fiber to polymers after various treatment times. Conventional surface treatment methods have been attempted for recycled carbon fiber, but most require very long processing times, which may increase cost. Hence, in this study, plasma processing was performed for 0.5s or less. Surface functionalization was quantified by X-ray photoelectron spectroscopy. O/C increased from approximately 11% to 25%. The micro-droplet test of adhesion properties and the mechanical properties of CFRP were also investigated.

Investigation into property control of VaRTM composites by resin infusion process

This paper proposes a property control method in vacuum-assisted resin transfer molding (VaRTM) using porous mold process (PMP) to fabricate carbon fiber-reinforced plastics (CFRP) composites. Low-cost VaRTM process generally induces the variation in quality and properties of fabricated composites, depending on infusion and curing process, dimension and configuration of stacked fabrics, etc. and involves difficulty in control of the properties of fabricated composites. As resin content in the composites can be easily controlled in VaRTM process combined with PMP, this paper investigates the effect of infused resin content on the final mechanical properties of CFRP. It is demonstrated that volume fraction of carbon fibers and the resultant mechanical properties of CFRP can be controlled by the infusion process control. Finally, application of the present control method to the manufacturing of a complex CFRP panel with thickness variation is demonstrated. It is concluded that the measured mechanical properties fit well with the designated properties.

Effect of Carbon Fiber Orientation and Helix Angle on CFRP Cutting Characteristics by End-Milling

Carbon Fiber Reinforced Plastics (CFRP) have outstanding lightweight material characteristics and tensile strength. The use of CFRP in aerospace industry has been successfully implemented and is expected to grow in the future. However, the mechanical properties of CFRP are affected by differences in the distribution and orientation of the carbon fibers and their adhesion to the binding material. CFRP shows intense anisotropy in strength of carbon fiber depending on its mechanical properties and the state of the carbon fiber orientation. Therefore, the tool life shortest and the surface finish quality of the material becomes unstable and eventually difficult to cut. This paper presents the effect on carbon fiber orientation and helix angle with CFRP cutting characteristics by end milling. Here, three types of orientations weremachined by straight type end mills and constant cutting conditions with a cutting speed 70 m/min, a feed rate 0.056 mm/tooth and 3 mm depth of cut. Our results showed that the tool helix angle 0° gave a better surface finish than the other tools, irrespective of the fiber orientation. The helix angle is greatly affected by the exposure of the fibers from the surface. Axial force (Fz) is negligible quantity for helix angle 0°, and cutting force is low. The carbon fiber orientation of 45° and -45° has exfoliation-like dimples.

Regulation of the mechanical properties of thermoplastic carbon fiber-reinforced plastics by changing their production conditions and surface treatment of the fibers

The effect of technological parameters of processing and surface treatment of carbon fibers on the mechanical properties of carbon fiber-reinforced plastics (CFRPs) was investigated. The copolymer of 1,3,5-trioxane with 1,3-dioxolane was used as the polymer matrix, and medium-modulus hydrated cellulose Ural LO-24 carbon fibers served as the reinforcing filler. The polymer matrix was mixed with the carbon fibers by the method of combined extrusion. The dependence of the mechanical properties of CFRPs on the technological parameters of screw-disk extrusion was studied. It was found that the properties of the composites were greatly affected by the size of the working disk gap, the disk rotation rate, and the temperature in the zone of normal stresses. The surface of the carbon fibers was activated with atmospheric oxygen in the temperature range of 450–600°C, with mass loss of the fibers no greater than 3–4%. A 30–40% increase in the mechanical properties of the CFRPs was achieved. A decrease in the melt index of the 1,3,5-trioxane copolymer with 1,3-dioxolane reinforced with oxidized carbon fibers was observed, which should be taken into account in processing the composites into products. Introduction of carbon fibers in the 1,3,5-trioxane copolymer with 1,3-dioxolane allows us to increase the wear resistance and decrease the friction coefficient, which makes it possibile to use these materials in the friction units of machines and mechanisms, such as plain bearings, gears, and flange packings.