Use Of Carbon Fiber Reinforced Plastics Research Articles

Recycling of wet carbon fiber-reinforced plastic laminates by thermal decomposition coupled with electrical treatment

The use of carbon fiber-reinforced plastics (CFRPs) produces moisture-absorbing CFRP waste, which is usually recycled via thermal decomposition treatment (TDT). However, the oxygen gas generated during heating can hardly penetrate dense CFRPs, resulting in nonuniform damage to the recovered carbon fibers (rCFs) collected from the outer (oCFs) and inner (iCFs) parts of CFRP waste. Herein, TDT was coupled with electrical treatment (ET) to improve the recycling performance of CFRP laminates waste. The tensile strength of the rCFs measured via the single-fiber tensile tests was analyzed using a two-parameter Weibull distribution. Absorbed water was preferentially evaporated from the laminates by Joule heating during ET, resulting in extensive pore formation. Following TDT, the oCFs and iCFs showed nearly identical average tensile strengths because the pores formed by ET served as efficient diffusion pathways for oxygen gas. The proposed recycling technology may potentially be applied to other types of moisture-absorption waste.

STUDY OF PREPREGS LIFETIME BASED ON EPOXY RESIN WITH AROMATIC AMINE HARDENER

Today, there is a steady trend in the use of carbon fiber-reinforced plastics in the aerospace and defense industries, mainly based on using pre-impregnated semi-finished products - prepregs. Producing carbon fiber parts from prepregs often requires a long manufacturing time, during which the prepreg must maintain its performance properties. Therefore, one of the main characteristics of prepreg is its viability. This work developed a suitable resin composition with optimized properties and a methodology for studying the viability of prepreg samples, based on determining the stickiness and degree of curing of the prepreg depending on storage time. The influence of prepreg storage time on the strength characteristics of cured laminates was studied. Prepreg samples with long-term viability of up to 60 days were obtained. The experimental data obtained are of practical significance in the industrial production of carbon fiber products, as they establish a connection between the performance properties of the prepreg and storage time.

Recycling and Reutilization of Waste Carbon Fiber Reinforced Plastics: Current Status and Prospects.

The extensive use of carbon fiber-reinforced plastics (CFRP) in aerospace, civil engineering, and other fields has resulted in a significant amount of waste, leading to serious environmental issues. Finding appropriate methods for recycling CFRP waste and effectively reusing recycled carbon fibers (rCFs) has become a challenging task. This paper presents an overview of the current status of CFRP waste and provides a systematic review and analysis of recycling technologies. In addition to discussing mechanical recycling, thermal decomposition, and chemical solvent degradation methods, the organic alkali/organic solvent method for recycling resins is also elucidated. By introducing the recycling conditions and outcomes of the organic alkali/organic solvent method, the study highlights its significance as a reference for carbon fiber recycling. Furthermore, the paper reviews the current state of rCFs utilization based on its application domains, focusing on research advancements in fiber composites and cementitious composites. Based on these findings, the paper summarizes the existing research limitations and identifies specific areas that require further attention in recycling techniques and rCFs utilization. Lastly, this review provides a prospect on the future of recycling and reusing CFRP waste.

Novel Approach toward the Forming Process of CFRP Reinforcement with a Hot Stamped Part by Prepreg Compression Molding.

The use of carbon fiber-reinforced plastics (CFRP) is markedly increasing, particularly for the manufacturing of automotive parts, to achieve better mechanical properties and a light weight. However, it is difficult to manufacture multi-material products because of the problems due to the adhesive between CFRP and steel. The prepreg compression molding (PCM) of laminated CFRP can reduce the production time and increase the flexibility of the manufacturing process. In this study, a new manufacturing process is proposed for CFRP reinforcement on a hot stamped B-pillar using PCM. A finite element (FE) simulation of the hot stamping process is conducted to predict the dimensions of the B-pillar. The feasibility of PCM manufacturing is explored by the simulation of the thermoforming of a CFRP set on a shaped B-pillar. The temperature conditions of the CFRP and B-pillar for the PCM are determined by considering the heat transfer between the CFRP and steel. Finally, the PCM of the B-pillar consisting of steel and CFRP was performed to compare with the analytical results for verification. The evaluation of the B-pillar was conducted by the observation of the cross-section for the B-pillar and interlayer by scanning electron microscopy (SEM). As a result, a steel/CFRP B-pillar assembly could be efficiently manufactured using the PCM process without an additional adhesive process.

Towards brittle damage in carbon fiber reinforced plastics: A gradient extended approach

This work is concerned with material modeling of carbon fiber reinforced plastics (CFRPs) with the prospect of application to shear cutting. It is assumed that the use of CFRPs for body parts is of great benefit in the field of lightweight construction. The presented material model distinguishes between damage in the isotropic and anisotropic part. It represents a special case of a more general thermodynamical framework. Furthermore, the micromorphic approach is used to overcome undesired mesh dependencies. A mesh convergence study is performed and the resultant force displacement curves are analyzed quantitatively. Tension tests are performed and the material model is fitted as well as tested on this data. The experimental data is used to justify the choice of the material model. Novelty of this work lies in an comparison of the crack paths of experiments and simulations. A direction dependence is included in the gradient term of the micromorphic extension to obtain the same crack paths in simulation and experiments.

Application of Eco-Efficiency Analysis to Assess Three Different Recycling Technologies for Carbon Fiber Reinforced Plastics (CFRPs)

The purpose of this paper is to evaluate the eco-efficiency of three different recycling technologies for carbon fiber reinforced plastic (CFRP) waste, and to identify the preferable and most efficient solution. Recycling via mechanical shredding, microwave pyrolysis and subcritical solvolysis is compared and comprehensive primary data on energy demand and process throughput are examined. Following an ecological and economic assessment, the results are normalized and summarized into three single-score indicators. To decide which solution is most efficient, economic and ecological data are plotted on an eco-efficiency portfolio. The achieved results demonstrate that the eco-efficiency of the recycling technologies investigated is entirely positive on an industrial scale, and that the efficient use of CFRPs across the entire life cycle is possible. The material recycling of CFRP waste is consequently a promising topic for future development. The use of recycled material as conductivity additives in secondary applications can be considered as a valuable option for all three technologies, although the benefits of recycling are strongly dependent on the quality and quantity of the recycled material. Depending on the resources substituted in a secondary application, different recycling technologies offer considerable advantages. To ensure a consistently high quality of output materials on an industrial scale, specific process parameters have to be identified, for which, further research is necessary.

Carbon fiber-reinforced plastics based on epoxy resin toughened with core shell rubber impact modifiers

AbstractThe weak impact properties of carbon fiber-reinforced plastics (CFRPs) are due to their laminated structure, thus limiting the use of these materials in various automotive applications even though they provide weight savings as compared with metal materials. In this study, core shell rubbers (CSRs), which are known for their excellent dispersion characteristics, were selected as an impact modifier and CFRPs incorporated with CSRs were fabricated using the vacuum-assisted resin transfer molding process to enhance their impact properties. CFRPs with highly reinforced carbon fibers of 72–74 wt.% were prepared without voids as confirmed by morphological and thermogravimetric data. The impact strength of the CFRPs was improved by up to 87.5%, depending on the increase in CSR content, but their tensile properties were not reduced, indicating that these properties were predominantly determined by the continuous reinforcement of carbon fibers. Therefore, CSRs are an effective impact modifier for improving the impact properties of CFRPs. These findings will help in increasing the use of CFRPs as automotive structural materials.

Cold and Warm V-bending Test for Carbon-fiber-reinforced Plastic Sheet

Although carbon-fiber-reinforced plastics (CFRPs) are the lightest and stiffest material, the use of CFRP is limited because of their higher price and lower formability than the other materials. We propose a method of stamping consolidated CFRP sheets. CFRP sheets are sandwiched by dummy metallic sheets in the stamping process. The dummy metallic sheets act as heating media, as well as protective materials for the CFRP sheets. In this paper, the springback angle of the specimens after the V-bending test under cold and warm condition was investigated and the fractures in formed CFRP sheets were observed.

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.

Laser Surface Pre-Treatment of CFRP for Adhesive Bonding in Consideration of the Absorption Behaviour

The use of carbon fibre-reinforced plastics (CFRP) is growing significantly in all areas of lightweight construction. Thermosets like epoxy still build a major part of deployed matrix material. A suitable joining technology for CFRP is adhesive bonding. However, the bonding performance is well reduced because of contaminations. To achieve full bond-strength, adhesion of the adhesive to the components is essential. One innovative method for surface pre-treatment is laser radiation. Former investigations show that an important parameter is the absorption. As a result of that, a UV laser (wavelength of 355 nm) and a CO2 laser (wavelength of 10600 nm) were used to pre-treat specimens manufactured from 120°C curing epoxy. The focus is to achieve a selective removal of resin without impairing the fibres. Lap-shear specimens have been pre-treated, bonded with an one component epoxy film adhesive and tested. The laser pre-treated specimens achieve the same bond strength as references prepared by manual abrading. Furthermore, the mechanisms of interaction between laser radiation and matrix material as well as fibres are discussed considering the different heat deposit and absorption behaviour of the emitted radiations.

Relationship of mechanical properties and temperature of carbon fiber-reinforced plastics under microwave irradiation

One of the problems with the use of carbon fiber-reinforced plastics (CFRP) is the difficulty of recycling or disposing of them. Hence, it is necessary to find processes to treat CFRP wastes faster and more effectively. Because carbon fibers are good microwave absorbers, there is significant potential for the use of microwave irradiation for the processing of CFRP wastes. In this study, the relationship of mechanical properties and radiation temperature during microwave irradiation of unidirectional and cloth-type CFRP were studied. Experimental results indicate that microwave irradiation degrades CFRP’s mechanical properties by breaking down the bond between the polymer matrix and the carbon fibers.

Surface Structuring of CFRP by using Modern Excimer Laser Sources

High demands for lightweight construction can be attained by the use of carbon fiber-reinforced plastics (CFRP) including one major challenge: the joining technology. Adhesive bonding may allow an increased utilization of the lightweight potential of CFRP. But this technology requires a surface pre-treatment because of residues of release agents. This paper describes surface pre-treatment of CFRP specimens by using modern excimer laser and the mechanical tests that compare the achieved strength to manually abraded ones. The laser process is suitable for achieving cohesive failure within the adhesive and bond strengths in the magnitude of the abraded specimen.

Design and Construction of Modern Bamboo Bridges

The writers are conducting a comprehensive research program, with the goal to develop modern bamboo structures for buildings and bridges. This paper reports the design, construction, and testing of modern bamboo bridges. Laminated bamboo girders or glubam were developed and verified for satisfactory mechanical performance through full-scale testing. It was demonstrated that the laminated bamboo girders have satisfactory stiffness and load carrying capacity. The use of carbon fiber-reinforced plastics can further enhance the stiffness and capacity of the bamboo girders. Based on the test results and analysis, a 10-m long single lane roadway bridge was designed and constructed, which was the first of its kind in the world. The field tests were carried out using an over loaded two-axel truck with a total weight of 8.6 t which exceeded the given design truckload of 8.0 t. The bridge performed satisfactorily with the midspan deflection corresponding to the critical service loading condition being much smaller ...

Use of carbon fiber-reinforced plastics in aircraft construction

1. Methods have been developed and perfected for calculating the deformation and strength characteristics of composite laminates in both the linear and nonlinear regions of behavior, with and without stress concentrations. 2. The properties of carbon fiber-reinforced plastics (CFRP) have been investigated experimentally for various reinforcing schemes, with and without stress concentrations, and at normal and elevated temperatures. It has been found that the loading rate in uniaxial tension affects the strength properties of the composite. 3. The fatigue characteristics of CFRP, with and without stress concentrations, have been investigated in asymmetric tension on a base of 106 cycles. The lifetimes are considerable and the fatigue curves have a shallow slope (m = 40). Cantilevel bending tests with a symmetric loading cycle and interlaminar shear tests, using the short-beam bending method, have also been carried out. 4. A procedure has been developed for calculating additional safety factors, taking as a basis the theory of reliability and the concept of probability of failure. 5. A unified finite-element method has been developed for calculating the stress-strain state of aircraft control surfaces made of composites and has been used to solve the problem of finding the optimum distribution of material (thickness and arrangement of the laminations) consistent with satisfaction of the static and acoustic strength requirements and possible technological constraints. 6. The results of using these methods to design the rudder of a supersonic passenger aircraft and the aileron and interceptor of a medium trunkline aircraft are presented. 7. The use of CFRP in such structures makes it possible to reduce the weight by on average 25% as compared with the weight of the metal structure and to improve the acoustic strength.

The use of carbon fibre-reinforced plastics in the construction of wings for testing in wind tunnels

The methods developed for the manufacture of wings from cold setting carbon fibre-reinforced plastics (cfrp) are described. On one particular aerodynamic design, wings were made from steel, glass-reinforced plastics (grp) and cfrp and the relative behaviour of these wings under load was obtained. In addition it has been shown that it is possible to produce moulded wings in cfrp to high dimensional accuracy.