High Modulus Carbon Fibers Research Articles

Clustering effect on mechanical properties and failure mechanism of open hole high modulus carbon fiber reinforced composite laminates under compression

The clustering effect of open hole high modulus carbon fiber (M40J) reinforced composite laminates under compressive load is studied with digital image correction (DIC), acoustic emission (AE) and high-resolution digital camera. Three types of quasi-isotropic laminates [45 m/0m/−45 m/90 m]ns (m × n = 4) with different clustering levels (m = 1, 2 and 4) are manufactured and tested to investigate their mechanical properties and failure mechanism. The experimental results indicate that as clustering levels increases, the open hole compressive strength gradually decreases accompanied by failure mode transferring from brittle fracture to delamination. Four types of sub-critical damages are found in the progressive failure process: splitting, delamination, layers buckling and layers compressive damage. The layers buckling and layers compressive damage can result in final failure of laminates yielding failure mode of delamination and brittle fracture, respectively. Besides, the effect of sub-critical damages and layer thickness on both mechanical properties and failure mode are discussed consequently obtaining the qualitative relationships between open hole compressive strength and material mechanical properties. The ratio of inter-fiber strength to layer longitudinal compressive strength is the crucial factor affecting the mechanical properties, and it should be controlled within the range where the push-in failure mode occurs for better properties.

Improving compressive strength of high modulus carbon-fiber reinforced polymeric composites through fiber hybridization

There has been a strong demand in using high-modulus (HM) carbon-fiber composites potentially enabling lightweight aircraft structures with significant weight savings. However, extremely low fiber-direction compressive strength has been a well-recognized weakness of the HM composites, prohibiting their implementation in aircraft platforms. Hybridizing fibers with varying moduli provides an innovative means for improving the fiber-direction compressive strength of composites. This has been implemented by comingling intermediate-modulus (IM) and high-modulus (HM) carbon fibers in HM carbon fiber-reinforced polymer (CFRP) toughened with nano-silica. Comingling IM and HM fibers at the filament level in addition to the matrix nano-sized structural reinforcement throughout the composite, increases shear modulus to axial modulus ratio of the composite material, thus improving microstructural stability likely governing the fiber-direction compressive strength behavior. The basis for this new material design stems from the fact that fiber-direction compressive strength increases with the shear modulus to axial modulus ratio of composites across different fiber and resin combinations. The results demonstrate that the new hybrid HM composite fiber-direction compressive strength achieves that of IM legacy composites but with more than 30% higher axial modulus.

High Strength and High Modulus Carbon Fibers “TORAYCA<sup>Ⓡ </sup>MX Series”

High Strength and High Modulus Carbon Fibers “TORAYCA<sup>Ⓡ </sup>MX Series”

Study on multistage anodization for high‐modulus carbon fiber

Because of the strong chemical inertness of high‐modulus carbon fiber (HMCF), the surface treatment of HMCF becomes less effective. In this work, multistage anodization method was applied to modify HMCF. NH4HCO3 and (NH4)2SO4 were used as electrolytes to study the influence of electrolyte type on the oxidation effect in the multistage oxidation process. The HMCF was treated by multistage anodization in the following three ways: NH4HCO3 → NH4HCO3, (NH4)2SO4 → (NH4)2SO4, and NH4HCO3 → (NH4)2SO4. In order to compare with the multistage anodization methods, HMCF was also anodized by NH4HCO3 and (NH4)2SO4 using single anodization method, respectively. The treated HMCFs were characterized in detail using X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, Scanning Electron Microscope (SEM), Atomic Force Microscope (AFM), and dynamic contact angle analysis, respectively. The results of XPS exhibited that HMCF modified by multistage anodization showed more functional groups on its surface. More sp2 hybridized bonds were converted into sp3 hybridized bonds after modification by multistage anodization, especially when (NH4)2SO4 was used as electrolyte. The results of SEM/AFM indicated that HMCF modified by multistage showed a greater surface roughness. Interlaminar shear strength (ILSS) was used to observe the interfacial properties of HMCF between epoxy resin. The results showed that ILSS of untreated carbon fiber composite was only 27.3 MPa; it was increased to 71.8 and 78.6 MPa after treated with single anodization by NH4HCO3 and (NH4)2SO4, respectively. After modification by multistage anodization, the ILSS increased in different degrees compared with single anodization method. Especially, the ILSS reached 93.1 MPa when the method of using NH4HCO3 followed by (NH4)2SO4 was used to treat HMCF.

Fe3O4/graphene modified waterborne polyimide sizing agent for high modulus carbon fiber

Reduced graphene oxide (RGO) loaded with magnetic Fe3O4 nanoparticles was synthesized through coprecipitation. Then, an Fe3O4/RGO-modified polyimide aqueous sizing agent was successfully synthesized with ultrasonic dispersion technology and coated on the surface of a high modulus carbon fiber (CF) under an applied magnetic field. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results show that the Fe3O4 with a cubic spinel crystal structure was successfully prepared. The morphology and particle size of the Fe3O4/RGO were characterized using transmission electron microscopy (TEM), indicating that Fe3O4 was uniformly dispersed onto the RGO sheet. Fourier transform infrared spectroscopy (FTIR) and a laser particle size analyzer proved that the aqueous dispersion of polyamic acid (PAA) was obtained with an average particle diameter of 158 nm. The mechanical property testing results showed that the interlaminar shear strength (ILSS) of CF/polyimide (PI) composites consisting of CFs coated with the Fe3O4/RGO-modified PI aqueous sizing agent under a magnetic field increased by 159.0%. This is attributed to the orientation of the Fe3O4 magnetic particles under a magnetic field that allowed them to be uniformly dispersed on the graphene, effectively weakening the potential for graphene agglomeration.

Effect of fiber microstructure studied by Raman spectroscopy upon the mechanical properties of carbon fibers

AbstractThe microstructure of polyacrylonitrile (PAN)‐based high‐performance carbon fibers, including high‐strength carbon fibers (HSCFs), high‐modulus carbon fibers (HMCFs), and ultrahigh‐modulus carbon fibers (UHMCFs), was systematically characterized by the Raman spectroscopy. Two characteristic bands, D‐line and G‐line, showed up in the Raman spectra of HSCFs, HMCFs, and UHMCFs. However, the wavenumber of the G‐line peak of HSCFs shifted to higher wavenumber (about 1,595 cm−1) and that of the D‐line peak of HMCFs and UHMCFs shifted to lower wavenumber (about 1,350 cm−1). The relationship between the microstructure and mechanical properties of carbon fibers was also studied in detail. It was of significant relevance between surface disordered structure and the mechanical properties of HSCFs, and decreases in the full width at half maximum values of the disorder‐induced D‐line and A‐line could result in higher tensile strength and tensile modulus of HSCFs. As for HMCFs and UHMCFs, the disorder‐induced D′‐line more easily affected the tensile strength. A higher tensile modulus of HMCF and UHMCF was obtained as a result of decreases in the disordered structure and increases in the graphite structure. An increase of the intensity ratio ID/IG together with IA/IG (HSCFs) or ID′/IG (HMCFs and UHMCFs) could result in increases in the tensile strength and tensile modulus of carbon fibers.

Experimental study of the flexural behavior of timber beams reinforced with different kinds of FRP and metallic fibers

This article involves a comparative study of the flexural behavior of timber beams reinforced with four kinds of unidirectional fiber (FRP) and metallic fibers attached to the outside using epoxy resins. The reinforcements were made using normal carbon fiber, high elastic modulus carbon fiber, glass fiber, basalt fiber and metallic fiber. Furthermore, three different test configurations were tested for each fiber type: one layer of material attached to the bottom, two layers of material attached to the bottom and two layers of material attached to the sides. The test involving unreinforced beams acted as a benchmark. The results show that reinforcing with fibers can substantially increase the initial resistance of the beams, the reinforcements made from lower elastic modulus fibers such as basalt and glass obtaining better results.

Effect of Volume Fraction of Reinforcement Layers on the Mechanical Properties of S-glass-Carbon-Epoxy Hybrid Composites

Abstract In the present study hybrid composites having various ratios of S-glass and high modulus Carbon fibres namely 100% S-glass(S-1), 80% S-glass with 20% Carbon(S-2), 60%-S-glass with 40% Carbon(S-3), 35% S-glass(S-4) with 65% Carbon, and 100% Carbon(S-5) with 0% S-glass were fabricated. Tensile strength, tensile modulus, flexural strength of these composites were measured. For samples S-2,S-3,S-4 modulus on both the faces (Carbon and S-glass side) were measured in a single tensile test to understand variation in elongation of Carbon and S-glass side of a hybrid composite as a function of applied load. Resultant tensile strength and modulus were compared with the predicted values using rule of mixtures. When either of reinforcements namely S-glass or Carbon is in lower proportion as compared to the other (S-2, S-4), the lower proportion reinforcement is behaving like the higher proportion reinforcement, in terms of its elongation showing the hybrid effect. When both reinforcements are in approximately equal proportions (S-3), then they are behaving like independent systems and thus showing significant deviation from predicted modulus. It is found that, as the high modulus Carbon fabric content was increased, there is a significant improvement in the modulus of the composite. However, the strength values were found to come down. Flexural strength of each of the hybrid composites was measured by applying bending load on sample from Carbon side as well as S-glass side separately. For the same composition of hybrid composite samples, when sample was loaded from Carbon side flexural strength was found to be 22.5% more strength as compared to the flexural strength when it was loaded from S-glass side. Reasons for the same were analysed using failure modes of composites and also from fracture toughness (K1C) of pure S-glass-epoxy (S-1) and pure Carbon-epoxy composite (S-5).With the help of opto digital microscope fracture morphologies were analysed and the reasons for the observed results trends were proposed.

Physico-mechanical properties of composite structural parts for machine tools

The paper is focused on experimental comparison of beam profiles made from welded steel, cast-iron and from fiber composites based on high-strength and high-modulus carbon fibers and epoxy resin. Three versions of composites were prepared with variation in their structure and composite lay-up. All the coupons were prepared with equal outer dimensions 130×130×1100mm. The coupons were tested to evaluate their static stiffness using three-point bending test, by experimental modal analysis to evaluate their mode-shapes with according frequencies and damping ratio and by heating to compare their deformation under thermal loading.

Evaluation of composite interfacial properties based on carbon fiber surface chemistry and topography: Nanometer-scale wetting analysis using molecular dynamics simulation

According to surface chemistry and topography of different high-modulus carbon fiber (HMCF), interfacial properties of various HMCF composite were evaluated, and nanoscale wetting analysis of HMCF were studied using experimental methods and molecular dynamics simulation. Hierarchical amount of active functional groups and nanoscale grooves were detected on the surface of pristine HMCF (p-HMCF), anodic oxidized HMCF (a-HMCF) and sized HMCF (s-HMCF). Remarkable enhancements in interfacial properties of a-HMCF and s-HMCF composites were obtained, which was ascribed to free-void interface from improved surface energy and wettability. Poor interfacial bonding of p-HMCF composites was due to generation of many nanobubbles with pinned contact lines during the wetting of the surface microgrooves with high aspect ratio and chemical inertness. Schematic of interfacial compatibility mechanisms was proposed to illustrate the correlation between surface features of carbon surface and interfacial properties of their composites.

Performance improvement in carbon fiber reinforced polymer-based composites

As the key strategic materials for national security, carbon fibers (CF) and CF reinforced composites must be independently guaranteed. Among them, the amount of carbon fiber reinforced polymer (CFRP) composite material accounts for more than 70% of carbon fiber composites. Resin matrix (content over 35 wt%) is one of the two basic materials of CF reinforced polymer composites, which directly determine the service performance and processing of the composites. The Advanced Composites Center (ACC) in Beijing University of Chemical Technology (BUCT) has carried out a series of fundamental and engineering research solve problems about how to prepare domestic high-performance resin matrix for carbon fiber with the aim of meeting the national strategic needs. ACC research team has made great progress in promoting domestic carbon fiber application and the innovation of high-performance domestic CF reinforced polymer composites. Since 2005, ACC research team have developed the resin matrix system and composites which are compatible with Toray T700/T800/T1000 carbon fibers and M40J, M55J high-modulus carbon fibers, and suitable for forming process with wide viscosity range. A series works have been conquered to promote the development of domestic carbon fibers from usable to easy-to-use. Research results have significantly improved the performance of domestic carbon fiber reinforced composites, optimized the preparation technology, and guaranteed the design and supporting capability of advanced weapons. In this paper, the research achievements and technical breakthroughs on CF reinforced polymer-based composites done by ACC research team in recent 10 years are summarized. The details include: (1) The cross-linking structure simulation of resin molecules used for CF. (2) Prediction of the relationship between molecular structure and properties of resins through molecule simulation method. (3) The new mechanism of double interface/double interphase and modulus transition layer for carbon fiber reinforced polymer composites. (4) The multiscale toughening and reinforcing methodologies of interfacial phases of carbon fiber reinforced polymer matrix composites. (5) In situ characterization of interface between carbon fiber and resin matrix composites through fluorescence matter. (6) Innovation of methodology for multi-stage/multi-scale toughening and strengthening of carbon fiber reinforced polymer composites. (7) Innovation in preparation technology of high performance resin materials used for carbon fiber. (8) Processing technology innovation and the related product engineering of CF reinforced polymer composites. The above-mentioned research works of BUCT have been supported by more than 30 projects, such as the National Military and Civilian Population Matching Project, the National Natural Fund Key Project and the National High Technology Research and Development Program (863) of China. And research results have been used in many key defense models of national defense industries, such as aerospace, weapons, nuclear industry, and aviation and so on. It has achieved considerable economic and social benefits and promoted the nationalization process of carbon fiber resin in the field of national defense. In the end, the development trend on high-performance CF reinforced polymer composites is generally prospected. And ACC research team will also tireless promote the whole life cycle usage of CFRP materials and contribute to the healthy and sustainable development of CFRP industry.

Manufacturing process and mechanical properties characterization for steel skin – Carbon fiber reinforced polymer core laminate structures

The research presented in this paper aims to introduce the manufacturing process and quantify the mechanical properties and fracture behavior of laminate structures made of thin steel skins and carbon fiber reinforced polymer core. For the skins, AISI-304 and AISI-1008 steels have been utilized whereas, for the core, an epoxy-matrix high-modulus carbon fiber reinforced polymer woven (0°/90°) is employed. Skins and core are bonded by a thin layer of Araldite420 epoxy-based adhesive. The mechanical properties of the laminate material have been characterized by means of 3-point bending test and the laminate material concept has been also utilized for the realization of simplified automotive B-pillar profiles, whose bending performances have been compared with B-pillar specimens made only of steel, showing a 48% improvement in the maximum bearable load.

Towards aerospace grade thin-ply composites: Effect of ply thickness, fibre, matrix and interlayer toughening on strength and damage tolerance

Thin-ply composites represent a promising approach to further improve the performance of carbon fibre composite structures thanks to their ability to delay the onset of matrix cracking and delamination up to the point of fibre dominated failure. However, this increased strength comes with a more brittle failure response which raises concerns on damage tolerance. Thus a careful material optimization is needed to address this trade-off. In this work, eight different formulations of thin-ply composites ranging from low modulus to high modulus carbon fibres are evaluated to understand the effects of the fibre and matrix constituents on the onset of damage and strength in unnotched tensile (UNT) tests of quasi isotropic laminates for ply thicknesses between 300 and 30 microns. The obtained experimental data are combined in master curve diagrams for simplified material selection process. It is observed that certain thin-ply composites with a ply thickness t < 134 μm can reach UNT strength corresponding to or approaching the ultimate strain of the fibres as well as UNT stress at onset of damage as high as 92% of the latter. Based on this knowledge, a novel aerospace grade toughened thin-ply composite system is developed which can reach a quasi-isotropic UNT strength above 1 GPa (>95% of the fibre strain). The newly developed composite is further optimized to improve damage tolerance by toughening the resin and selected interfaces. The effect of those modifications on damage tolerance are evaluated through compression strength after impact (CAI) tests and open hole tensile tests (OHT). It is found that an optimized interlayer toughened thin-ply composite based on 68 microns plies of intermediate modulus fibre can reach both outstanding strength properties with comparable or better CAI and OHT strength compared to current aerospace grade composites.

Siloxane Precursor-Based Protective Coatings for High Modulus Carbon Fibers in Ceramic Matrix Composites

Carbon fibers are outstanding reinforcements for ceramic components due to their excellent creep and long-term thermochemical and thermomechanical stability. Nevertheless, these properties are dramatically downgraded if the unprotected fibers are exposed to an oxidative or corrosive environment. Thin ceramic coatings can improve the corrosion resistance and tailor the fiber/matrix interface in order to achieve optimized stress transfer and damage tolerance. The continuous liquid phase coating (CLPC) technique with subsequent pyrolysis is a promising alternative to chemical vapor deposition (CVD) processes. The possibility to deposit homogenous thin flaw-free coating layers on every filament of high tenacity carbon fiber bundles has been successfully proven in previous studies. In this work, high modulus carbon fibers were coated with different polysiloxane-based resins, and the obtained rovings were implemented in SiOC matrices by the precursor impregnation and pyrolysis (PIP) route. Thermogravimetric analysis shows an increased oxidation resistance of the coated fibers compared with reference samples. Enhanced fiber/matrix interface strength further improved the mechanical performance of the fabricated composites.

Evolution of microstructure and electrical property in the conversion of high strength carbon fiber to high modulus and ultrahigh modulus carbon fiber

Evolution of microstructure and electrical property in the conversion of high strength carbon fiber (HSCF) to high modulus carbon fiber (HMCF) and ultrahigh modulus carbon fiber (UHMCF) was investigated. Longitudinal grooves on fiber surfaces became less well-defined during high temperature graphitization. The tensile modulus of carbon fibers was affected by fiber crystalline structure and it increased with decreases in the value of interlayer spacing and improvements in the value of crystallite thickness. Increases in the crystallite size almost had little effect on the tensile strength. However, a lower interlayer spacing and a higher preferred orientation could result in a higher tensile strength. The crystal structure of carbon fibers became much more ordered during high temperature graphitization. It was found that the electrical resistivity gradually decreased from 14.69 × 10−4 Ω·cm to 9.70 × 10−4 Ω·cm and 8.80 × 10−4 Ω·cm, respectively, in the conversion of HSCF to HMCF and UHMCF.

Enhanced interfacial and mechanical properties of high-modulus carbon fiber composites: Establishing modulus intermediate layer between fiber and matrix based on tailored-modulus epoxy

Tailored-modulus epoxy matrix was designed on basis of surface analysis of high-modulus carbon fibers (HMCF), and the effects of modulus intermediate layer on interfacial and mechanical properties of HMCF composites were investigated. Narrow grooves and active functional groups were detected on HMCF surface. The modulus of epoxy was tuned by stiff organic molecular structure of cycloaliphatic epoxy (CE) and amide acid (AA). Modulus intermediate layer was established along with modulus gap shrinkage and interphase extension between HMCF and high-modulus epoxy, causing remarkable improvements in interfacial properties of composites. Schematic model of interphase reinforcing mechanism was proposed, and modulus intermediate layer with a platform in the composites with high modulus epoxy matrix could facilitate the shift in stress concentration and suppress initiation and propagation of cracks, which resulted in improved mechanical properties of HMCF composites by enhancement of interfacial bonding and stress transfer capability between fiber and matrix.

Hybrid effect and pseudo-ductile behaviour of unidirectional interlayer hybrid FRP composites for civil engineering applications

An experimental study on the tensile stress-strain curves of interlayer (layer-by-layer) unidirectional hybrid FRP composites was conducted aiming at evaluating the corresponding hybrid effect and pseudo-ductility of this innovative solution. Different combinations of the following dry unidirectional fabric materials, also varying the number of layers, were adopted in tests: high-modulus carbon, standard carbon, E-glass, and basalt. The composites were produced layer-by-layer by hand lay-up method, using an epoxy-based resin as matrix.The results have shown a strain increase at failure of both standard carbon and high-modulus carbon fibres with the volume decrease of these materials in hybrid combinations. It was also concluded that combining high-modulus carbon with E-glass, high-modulus carbon with basalt, or high-modulus carbon with standard carbon can lead to very good pseudo-ductile tensile behaviour. Finally, it should be highlighted that an existing analytical model in the literature was satisfactorily adopted to predict the tensile response of these hybrid composites.

Novel carbon fibers reinforced composites based on polysulfone matrix

The aim of this study is to create composites based on the high-temperature polymer reinforced with the carbon fibers and to study interfacial interaction between carbon fibers and polymer matrix. We propose a new method to obtain polysulfone based composite materials reinforced with high-modulus carbon fibers. The influences of thermal oxidation of carbon fibers on mechanical and thermal properties of the composites were studied. It was found that the obtained composite materials have sufficiently high mechanical properties, tensile strength up to 1047 MPa and Young’s modulus up to 70.9 GPa were found. Considerable interest to the polymer composites is associated with their high performance and good mechanical and thermal properties, which enable a broad range of aerospace, automotive and medical applications. Additionally, the manufacturing process of such composites can easily be optimized and automatized, furthermore, it is not time-consuming process in relation with thermosetting polymer based composites.

Sorption properties of PAN-based carbon fiber corrugated by ion irradiation

The sorption properties of the corrugated surface of PAN-based high-modulus carbon fiber by high-fluence irradiation with 30keV Ar+ ions at the irradiation temperature of T=220-230°C have been studied. The effect of carbon fiber corrugation leads to a multiple increase in specific surface area. Analysis of the specific surface area data for irradiated and non-irradiated fiber has been shown the influence of corrugation on increasing in sorption capacity and distribution of mesopores by size

Physical and mechanical properties of high-modulus carbon fiber crimped by ion irradiation

The experimental results of ion-induced crimping of the high-modulus carbon PAN-fibers using nitrogen, neon and argon ions with energies of tens keV are presented. Ion-induced surface nanostructuring of the formed crimps provides more than a hundredfold increase in the specific surface area of the fiber and its shrinkage that retains in thermal processes in the production of composites.