Carbon Fiber Reinforced Epoxy Composites Research Articles

Effect of Low-Temperature Plasma Surface Treatment on Bonding Properties of Single-Lap Joint of Thermosetting Composites

Bonding is one of the main forms of composite bonding. In order to investigate the effect of low-temperature plasma surface treatment on the bonding properties of carbon fiber-reinforced epoxy resin composites (CF/EP), a single-lap joint of CF/EP was prepared. The surface of the CF/EP was treated with atmospheric pressure "low-temperature plasma spray" equipment, and the tensile shear strength, surface morphology, surface contact angle and surface chemical composition of the CF/EP before and after plasma treatment were characterized. Finally, the samples were treated with traditional sandblasting, compared and analyzed. The results show that the effect of low-temperature plasma surface treatment on CF/EP joints is better than that of traditional sandblasting treatment. After low-temperature plasma surface treatment, the tensile shear strength of the CF/EP single-lap joint increased by 119.59% at most, and the failure form of the joint changed from untreated interface failure to mixed failure dominated by cohesion failure. Plasma can etch the surface of composite materials, the mechanical interlock between the carbon fiber and glue is enhanced and the bonding performance of the composite is improved. In addition, after low-temperature plasma surface treatment, the introduction of a large number of oxygen-containing active groups such as C-O and C=O can increase the surface free energy, reduce the contact angle and improve the surface activity and wettability of the composites. However, too long a treatment time will lead to excessive plasma etching of carbon fibers, thus weakening the active effect of the oxygen-containing active groups on the surface of the composites, and the surface wettability is no longer improved, but the adhesive properties of CF/EP are reduced. This paper plays a guiding role in the bonding technology of composite materials.

Enhancements in LOX compatibility and fracture toughness of carbon fiber/epoxy composite for liquid oxygen cryotank by simultaneously introducing Al(OH)3 and phosphorous-nitrogen flame retardants

Simultaneously enhancing the liquid oxygen (LOX) compatibility and fracture toughness at the cryogenic temperature of carbon fiber reinforced epoxy (CFRE) composites is critical for their successful application in LOX cryotanks. Herein, based on our previous work on optimizing the phosphorous-nitrogen containing organic flame retardant (TAD) content in epoxy resin for achieving the best LOX compatibility, the EP resins and CFRE composites modified with further incorporating inorganic flame retardant Al(OH)3 were fabricated. Specifically, the effects of introducing Al(OH)3 particles on the LOX compatibility and mechanical performances particularly at 90 K were thoroughly investigated. The results indicate that the Al(OH)3/TAD-EP resin (hence CFRE composite) with 4 phr Al(OH)3 exhibits an outstanding LOX compatibility without any impact reaction of burning, explosion, flash and charring observed in 20 samples. Moreover, the mode II fracture toughness of CFRE composites at room temperature and 90 K is improved by 27.3% and 16.7%, respectively with the addition of 4 phr Al(OH)3. Benefited with the simultaneous incorporation of 15 phr TAD and 4 phr Al(OH)3, the CFRE composite is promising for application in LOX tanks.

Impact of graphene nano particles on tribological behaviour of carbon fibre reinforced composites

ABSTRACT The purpose of this investigation is to see how varying percentages of Graphene Nanoplatelets (GNP) affect the wear behaviour of carbon fibre reinforced epoxy (CFRE) composite. The hybrid nano composites were developed using hand layup process followed by compression moulding. Furthermore, the impact of operational parameters such as load and abrading distance against SiC paper of 220 grit size at a rotational speed of 200 rpm was investigated. It was found that incorporating a considerable amount (up to 0.5 wt. %) of GNP significantly improved the wear performance of CFRE composites. There is increase in wear loss again for 0.75 and 1.0 wt. % GNP. The morphology of developed nano hybrid composites were linked to data patterns on wear volume and specific wear rates. GNP addition up to 0.5 wt. % strengthened the fibre-matrix interface, preventing simple fibre pull-out from matrix/fillers and enabling increased wear resistance, according to worn surface characteristics investigation.

Healable carbon fiber reinforced epoxy composites: Synchronous healing of matrix and interface damage

AbstractThermosetting composites are a range of high‐performance materials with important applications in multiple fields. However, inaccessible damage such as microcracks ingress from the environment may appear with long term use. Over time, the micro‐damage further expands and leads to material failure. The damage includes the interface damage and the matrix damage. Therefore, the healing technology of composites needs to respond and heal the micro‐damage of the interface and resin in the composites synchronously. In this work, siloxane dynamic bond was introduced into matrix and interface respectively. Specifically, a new type of crosslinker containing polysiloxane was synthesized and used to cure epoxy resin. Polyhedral oligomeric silsesquioxane was modified on the surface of carbon fibers (CFs) by sizing method. The prepared resin showed great mechanical properties and thermal stability, while the mechanical strength and surface activity of the CFs were also improved. Due to siloxane chain exchange reaction, matrix and interface could healing synchronously with good healing efficiency. Furthermore, the composites could retain about 65% of their original mechanical properties after healing multiple times. Composites realized synchronous healing of the resin matrix and the interface and laid foundation for extending the service life and performance of advanced resin‐based composites.

Mechanical properties and wear resistance of Cf / epoxy resin composites with in-situ grown SiC nanowires on carbon fibers

ABSTRACT Carbon fiber-reinforced resin matrix composites have been utilized as structural and bearing parts in aerospace because of their high specific strength and modulus. To improve the mechanical properties and wear resistance of carbon fiber-reinforced epoxy resin composites, we propose the in-situ growth of SiC nanowires on the surface of carbon fiber by a Chemical Vapor Deposition method. The effect of the addition of nanowires on the mechanical strength and wear resistance of carbon fiber-reinforced epoxy resin composites was investigated. The results indicated that the tensile strength and bending strength of SiCnws / C f / epoxy resin composites increased by 13.8% and 16.2% on the condition that the concentration of Ni(NO3)2 catalyst was 0.1 mol/L, respectively. The improvement of the mechanical properties could be attributed to the mechanical interlocking affection between carbon fiber and SiC nanowires. In addition, due to SiC nanowires with a three-dimensional network structure on the surface of carbon fiber, the stronger adhesive force between epoxy matrix SiC nanowires protected the resin matrix and carbon fiber from abrasion. The wear rate of SiCnws / C f / epoxy composites was reduced by 98.1%.

Experimental assessment of barely visible impact damage carbon fibre reinforced epoxy composite using ultrasound method

Background: Carbon fibre reinforced epoxy (CFRP) is susceptible to impact damage which could resulted in reduction of the mechanical properties. This paper studies the architecture of barely visible impact damage (BVID) to comprehend the extent of damage on quasi-isotropic CFRP laminates of varying thickness (i.e. 16, 24 and 32-ply laminates of 3, 4 and 5 mm respectively). Methods: Quasi-static indentation is chosen to produce BVID on CFRP laminates, followed by using non-destruction evaluation method, namely conventional contact-type ultrasonic testing (UT) and C-mode scanning acoustic microscopy (C-SAM) method. Results: The findings revealed (1) the size and shapes of the BVID on CFRP laminates, (2) no damage found at the point of damage, and (3) the bridging between the point of impact to the outer damaged diameter due to the consequence of diverse orientation of carbon fibre strips which exhibit excellent mechanical properties before structural failure. Conclusions: The results concluded that the UT and C-SAM method can identify both the pristine region and the internal damaged structures in CFRP laminates.

Porous, low thickness carbon-fiber reinforced epoxy composites with excellent flexibility and superior electromagnetic radiation protection

Fiber reinforced polymers, especially carbon fiber reinforced polymers, are expected in the future to contribute more than 50% of the structural mass of an aircraft. With increasing application and experience increased attention is paid to carbon-fiber reinforced composites with improved advanced properties, such as mechanical, structural and electrical, allowing them to displace the more conventional materials, such as metal alloys. In this paper, we used the Design of experiment methodology to investigate the design and properties of newly developed unique porous carbon-fiber reinforced composites intended for electromagnetic shielding purposes. The main goal was therefore to fabricate a composite with low thickness, high permeability to air and water vapor with a satisfactory ability to shield electromagnetic fields, whereas the investigation of the influential variables of the reinforcement and the investigation of the influence of the matrix on the overall shielding efficiency of the composite belongs to the sub-objectives. Furthermore, other important properties of the composites including heat and mass transfer, mechanical and electrical properties were evaluated. A quality index evaluation approach using weighted and normalized data was implemented to choose a composite with properties, which best fits to its intended use. The highest quality index was achieved by the composite containing reinforcement with warp and weft sett 18 dm−1 using carbon tape 2 mm wide. This composite provides electromagnetic shielding 36 dB at 1.5 GHz, having high air permeability 1000 mm/s, relatively low bending rigidity of around 2.5 Nmm and thickness of only 0.37 mm.

Poly(methyl methacrylate) as Healing Agent for Carbon Fibre Reinforced Epoxy Composites.

Self-healing materials offer a potential solution to the problem of damage to fibre-reinforced plastics (FRPs) by allowing for the in-service repair of composite materials at a lower cost, in less time, and with improved mechanical properties compared to traditional repair methods. This study investigates for the first time the use of poly(methyl methacrylate) (PMMA) as a self-healing agent in FRPs and evaluates its effectiveness both when blended with the matrix and when applied as a coating to carbon fibres. The self-healing properties of the material are evaluated using double cantilever beam (DCB) tests for up to three healing cycles. The blending strategy does not impart a healing capacity to the FRP due to its discrete and confined morphology; meanwhile, coating the fibres with the PMMA results in healing efficiencies of up to 53% in terms of fracture toughness recovery. This efficiency remains constant, with a slight decrease over three subsequent healing cycles. It has been demonstrated that spray coating is a simple and scalable method of incorporating a thermoplastic agent into an FRP. This study also compares the healing efficiency of specimens with and without a transesterification catalyst and finds that the catalyst does not increase the healing efficiency, but it does improve the interlaminar properties of the material.

Closed-loop recycling and degradation of guaiacol-based epoxy resin and its carbon fiber reinforced composites with S-S exchangeable bonds

The waste and desertion of petroleum-based epoxy resins have attracted increasing concerns on the damage and pollution to the environment because they are difficult to reprocess and reuse after curing. Once broken or injured, the recovery or degradation of composites is a tough challenge owing to their permanently cross-linked networks. In this paper, a novel guaiacol-based epoxy resin (BGF-EP) was prepared from renewable resources instead of conventional petroleum-based bisphenol A, curing with 4-aminophenyl disulfide (AFD). The epoxy vitrimer BGF-EP-AFD had appreciable thermal stability (Tg:143 °C, Td5%:295 °C), sufficient mechanical properties (tensile strength:55.54 MPa, elongation at break:12.23%) and stress relax from 300 min at 130 °C to 27.5 s at 200 °C. And the vitrimer could be reprocessed into a complete film. More excitingly, an efficient strategy was proposed to dissolve the cured resin and recycle its carbon fiber reinforced composites in a closed loop in an appropriate mixing solution (50%DMF/50%β-ME) at room temperature. The recovered carbon fibers are not altered and remain intact for the next utilization as confirmed by SEM. This work contributes the development of guaiacol-based renewable functional materials and provides a feasible and economical way to recycle and reprocess the carbon fiber reinforced epoxy composites.

New designs of sandwich panels to mitigate high-frequency noise inside space vehicles

Radiation of noise to the interior of a space vehicle during liftoff and transonic climb is a long-standing problem. To attenuate noise inside the crew compartment during launch and in-space operation, sandwich panels have been employed in the pressurized outer shell to passively reduce the exterior noise transmission. However, the layouts and the sound transmission loss of the implemented sandwich panels have not been made available for public release. Against this idiosyncratic practice, this study envisioned disseminating the know-how on the sound attenuation ability of dissimilar sandwich panels. To efficiently absorb and dampen the acoustic energy, the sandwich panels were specifically configured using a honeycomb core, felts and a closed cell aluminum-foam in the material lay-up. The face sheets of the sandwich panels consisted of either glass fiber-reinforced epoxy or carbon fiber-reinforced epoxy composites. The sandwich panels were tested as acoustic barriers to a diffuse sound field in a sound transmission suite. As found, an increase in the panel thickness brought a decrease in the anti-symmetric coincidence frequency of sandwich panels. A rubber damping layer in the material lay-up added limp mass to a sandwich panel and reduced the panel vibration at excitation frequencies beyond 500 Hz. Multiple felts reinforced the sound transmission loss of a sandwich panel by dissipating the acoustic energy into thermal energy at the felt interstices in the frequency regime beyond 315 Hz. In conclusion, this study proposed optimized sandwich configurations considering the constitutive materials, number of material layers, material layer thickness and stacking sequence. The optimized sandwich configurations could fairly deliver the demanded sound transmission loss in the high-frequency regime.

Mechanical properties of carbon fiber reinforced with carbon nanotubes and graphene filled epoxy composites: experimental and numerical investigations

The mechanical properties of carbon fiber-reinforced epoxy composites were identified by adding carbon-based nano-reinforcements, such as multi-wall carbon nanotubes (CNTs) and graphene platelets (GP), into the epoxy matrix by conducting suitable experiments. The main focus of this study is to compare the tensile modulus, tensile strength, flexural modulus, flexural strength, and thermal conductivity of carbon fiber-reinforced epoxy composites with nanoparticle reinforcement. The results revealed that adding CNTs and GP nanoparticles improved the mechanical properties compared to a pure carbon fiber-reinforced plastic composite. However, compared to CNTs, the GP’s addition has increased the mechanical properties of the CFRP composite. In addition, scanning electron microscopy (SEM) images were presented to explore the microstructural characterization of carbon fiber-reinforced nanoparticle-reinforced composites. Further, using numerical studies, the transverse modulus, major and minor Poisson’s ratio of the carbon fibre reinforced with CNT and GP particle reinforcement were estimated. The current study is applied to the efficient design of nanoparticle reinforced carbon fibre reinforced composites.

Drilling Response of Carbon Fabric/Solid Lubricant Filler/Epoxy Hybrid Composites: An Experimental Investigation

Carbon-fiber-reinforced epoxy composite (CEC) has gained widespread acceptance as a structural material in various applications. Drilled holes are essential for assembling composite material components. Reducing drilling-induced damage and temperature effects is crucial for improved surface quality and integrity of the drilled composite. In the present work, drilling experiments were conducted on CEC, hexagonal-boron nitride (h-BN) dispersed CEC, and molybdenum disulfide (MoS2) dispersed CEC at three different levels of spindle speed, feed, and drill diameter using solid carbide twist drills. The filler concentrations used in this study were 4, 6, and 8 wt%. Analysis of variance (ANOVA) was used to determine the significance of input factors (feed, spindle speed, drill diameter, and filler concentration) on the drilling responses such as thrust force, temperature, arithmetic mean surface roughness (Ra), and push-out delamination factor (DFexit). The average drilling temperature, Ra, and DFexit of MoS2 dispersed CEC were reduced by 24.7, 46.5, and 11.3%, respectively, when compared to neat CEC. In h-BN dispersed CEC, the average drilling temperature, Ra, and DFexit were reduced by 25.2, 40.9, and 13.2%, respectively, compared to neat CEC. The lubricating properties and high thermal conductivity of filler added to epoxy are responsible for the lower temperature and improved hole surface finish. The improved delamination resistance in filler-loaded CEC is due to the strengthening of the matrix and fiber–matrix interface. Scanning electron microscopy (SEM) was used to examine the morphology of the drilled composite surface. The spindle speed of 5500 rpm, feed of 0.03 mm.rev−1, and filler loading of 4 wt% produced the minimum Ra and DFexit. The response surface method (RSM) was applied to determine the input parameters based on multi-response optimum criteria.

Constructing network-shaped hydroxyapatite interlayer for carbon fiber composites

Hydroxyapatite interlayer was designed and fabricated in carbon fiber reinforced epoxy composites (COE), forming carbon fiber-hydroxyapatite-epoxy ternary composites (CHE). The microstructure, mechanical and biotribological properties of CHE were investigated. The hydroxyapatite interlayer grew uniformly on the surface of carbon fibers, exhibiting network morphology with numerous micrometer-scale pores. The tensile strength and the elastic modulus of CHE were increased by 17.8% and 90.1%, respectively compared with that of COE. The friction coefficient of CHE was increased by 23.5% and the wear rate of CHE was reduced by 28.3%. These results demonstrated the potential application CHE in human bone replacement.

High-performance, intrinsically fire-safe, single-component epoxy resins and carbon fiber reinforced epoxy composites based on two phosphorus-derived imidazoliums

Carbon fiber reinforced polymer (CFRP) composite is a kind of lightweight material with excellent comprehensive properties, but low production efficiency and inherent flammability have become two crucial limitations for its further application. Herein, two phosphorus-derived imidazoliums (CEPM-1 and CEPM-2) were synthesized by aqueous self-assembly, and applied to flame-retardant, one-component epoxy resins (EPs). Moreover, the well-designed EPs (EP/CEPM-1–25 and EP/CEPM-2–20) were used as resin matrixes for CFRP. Both EPs featured superior latency and modest-temperature fast curing, especially EP/CEPM-1-25, which had a long shelf life of 30 days and can gel within 20 min at 150 °C. The limiting oxygen index (LOI) and UL-94 classification of EP/CEPM-1-25 were 33.0% and V-0, indicative of superior flame retardancy. The total smoke production and maximum smoke density of EP/CEPM-1-25 displayed 37.7 and 72.1% reductions relative to those of the control EP sample cured by imidazole, demonstrating improved smoke suppression. EP/CEPM-2-20 also displayed satisfactory fire safety, but slightly inferior to EP/CEPM-1-25. As expected, the CFRP composites based on EP/CEPM-1-25 and EP/CEPM-2-20 showed high LOIs (42.5 and 39.0%) and UL-94 V-0 classification due to the inhibition of P-containing groups in CEPM-1 and CEPM-2 on the wick effect. Therefore, this work proposes a facile and ‘green’ methodology to create high-performance, intrinsically fire-safe single-component EPs and CFRP composites.

Effect of ceramic particles on the mechanical and tribological properties of short carbon fiber reinforced epoxy composites

Effect of ceramic particles on the mechanical and tribological properties of short carbon fiber reinforced epoxy composites

IMPROVEMENT OF SURFACE PROPERTIES OF CARBON FIBER REINFORCED EPOXY COMPOSITES USING SOLID LUBRICANTS DURING MACHINING PROCESSES

Polymeric composites become the most common alternatives for traditional metallic materials for a wide range of industrial applications, in the automotive industry polymeric materials and polymeric composites replaced a huge percentage of metallic parts. Polymeric composites are light in weight, easy to form, and have a lot of other properties that are recommended for automotive and other industries. But - on the other hand- the machining of polymeric parts has restrictions and limitations because of the likelihood of damage to these parts during machining operations. Cracks, tears, fiber pull-out, softness, fracture as well as surface roughness are common examples of damage to polymeric composites while machining. The present work is concerned with measuring of surface finish and generated temperature of machined parts during the drilling of carbon fiber-reinforced composites. Reducing surface roughness and machining temperature are the objectives of this work to improve the ability of polymeric composites to be safely drilled (machined). The proposed polymeric composites consist of epoxy reinforced with carbon fiber as well as some fillers to enhance the machining properties of epoxy composites. The results show that using metallic fillers (copper powder, MoS2 powder) under selected cutting conditions remarkably improved the machinability of carbon fiber-reinforced epoxy composites.

Effect of ply thickness on tensile and bending performances of carbon fiber reinforced thermoplastic unidirectional laminate

AbstractIt has been explored that thin ply would improve the mechanical performances of carbon fiber reinforced epoxy composites laminate. It has not been known whether there are similar effects on thermoplastic composites. In this article, carbon fiber reinforced polyamide 6 (CF/PA6) unidirectional fabrics with two thicknesses of 0.045 and 0.105 mm were used to fabricate the unidirectional laminate (UDL). Tensile and bending behaviors of the UDL were recorded with a digital image correlation (DIC) system, their damage macro‐morphologies were observed with high‐speed camera during loading. The fracture microstructures of the samples were observed with SEM and optic microscope. The results showed that the tensile and bending strengths of the samples with 0.045 mm thick are 79.8% and 24.8% higher than that with 0.105 mm thick. Thinning ply can inhibit the crack expanding, and the time from crack originating to fracture of the sample is larger than that of the thick ply one. Morphologies of the fractures revealed that the crack mainly expanded in the matrix along the loading direction for thin‐ply laminate, while the crack developed in the fiber cluster for thick‐ply laminate. The results also revealed that the mechanical properties of the laminate can be improved obviously by using thin‐ply.

An experimental study on the sound transmission loss of dissimilar fuselage sandwich panels of turbojet aircraft

The analysis of acoustic performance of sandwich panels, designed explicitly for fuselage sidewalls of turbojet aircraft, has been revisited numerous times. However, the layouts and the sound transmission loss of the airborne fuselage sandwich panels have not been made available for public release. Against this idiosyncratic practice, this study envisioned disseminating the know-how on the sound attenuation ability of dissimilar sandwich panels implemented in the fuselage of turbojet aircraft. To efficiently absorb and dampen the acoustic energy, the sandwich panels were systematically configured using a honeycomb core, felts and a closed cell aluminum-foam in the material lay-up. The face sheets of the sandwich panels were composed of either glass fiber-reinforced epoxy or carbon fiber-reinforced epoxy composites. The sandwich panels were tested as acoustic barriers to a diffuse sound field in a sound transmission suite consisting of two adjacent sound reverberation rooms. As found, a rubber damping layer in the material lay-up of a sandwich panel reinforced the sound transmission loss at frequencies beyond 500 Hz. Multiple felts augmented the sound transmission loss in the frequency regime beyond 315 Hz. The panel edges needed to be sealed properly to reproduce the sound transmission loss of a sandwich panel in successive experiments. This study leveraged many-faceted insights into the configuration (constituent materials, number of material layers, thickness, and stacking sequence) of commercially feasible sandwich panels. Besides, this study proposed optimized sandwich configurations based on the sound transmission loss, which will help aircraft manufacturers to apply these sandwich panels without further modifications.

Characterization of aerosolized particles in effluents from carbon fibre composites incorporating nanomaterials during simultaneous fire and impact

This work investigates the aerosols emitted from carbon fibre-reinforced epoxy composites (CFC) incorporating nanomaterials (nanoclays and nanotubes), subjected to simultaneous fire and impact, representing an aeroplane or automotive crash. Simultaneous fire and impact tests were performed using a previously described bespoke testing methodology with the capability to collect particles released from the front/back faces of the impacted composites plus the effluents. In this work the methodology has been further developed by connecting the Dekati Low Pressure Impactor (DLPI) and Mini Particle Sampler (MPS) sampling system in the extraction chimney. The aerosols emitted have been characterized using various devices devoted to the analysis of aerosols. The influence of the nanoadditives in the matrix on the number concentration and the size distribution of airborne particles produced, was studied with a cascade impactor in the 5 nm–10 μm range. The morphology of the separated soot fractions was examined by SEM. The measurement of aerodynamic size of particles that can deposit in human respiratory tract indicate that 75% of the soot and particles released from CFC could deposit in the lungs reaching the bronchi region at a minimum. There was however, a minimal difference between the number particle concentrations or particle-size mass distribution of particles from CFC and CFC containing nanoadditives. Moreover, no fibres were found in the effluents.

Mechanical Characterization of Balsa Wood, Depron and Glass Fiber Composite for Aircraft Floor Panel and Luggage Compartment

The present materials record greatest usage of composites in automotive and aircraft industry. Parts of aircrafts are experimenting materials with respect to mechanical properties which should have more strength to weight ratio, resistance to buckling, high ultimate tensile strength, high resistance to vibration, and high fatigue. Composite materials filled the requirement for making high strength to weight ratio components. This paper aims to study the Mechanical Characterization of Balsa wood, Depron and Glass fiber. The fabricated composites is highly suitable for manufacturing of floors in aircrafts instead of carbon fiber reinforced epoxy composite. Also, it will be used for luggage compartment. Using Hand Layup process specimens were prepared and the tensile test, Temperature Test and Flexures test has been performed as per ASTM standard. We observed 12%-17% more bending strength from this experiment which suits well for aircraft floor panel.