High Modulus Carbon Research Articles

Enhanced Interfacial Properties of High-Modulus Carbon Fiber Reinforced PEKK Composites by a Two-Step Surface Treatment: Electrochemical Oxidation Followed by Thermoplastic Sizing

Enhanced Interfacial Properties of High-Modulus Carbon Fiber Reinforced PEKK Composites by a Two-Step Surface Treatment: Electrochemical Oxidation Followed by Thermoplastic Sizing

Threshold properties of high modulus carbon fiber reinforced plastic composite with picosecond laser processing

The picosecond laser processing thresholds and morphology characteristics of polyacrylonitrile-based high modulus carbon fiber reinforced cyanate ester composite (M55/BS-4) and an asphalt-based high thermal conductivity carbon fiber reinforced plastic (K600/5418) were studied. Diameter-regression method was used to test and compare the ablation threshold, threshold incubation effect, and single-pulse thresholds for each composite were predicted. The influence of incident energy fluence (0.7-25 J/cm2) and beam scanning velocity (0.2-5 m/s) on the incision quality was analyzed. The results show that the great difference in the fiber thermal conductivity leads to significant quantitative difference in processing threshold and morphology. Using the highest scanning speed (5 m/s) available and fluence equivalent to 3.2 times the single-pulse threshold (i.e., about 8 J/cm2), carbon fiber and resin can be almost synergically removed, characterized by uniform slit inlet widths and neat cutting edge. The use of higher scanning speeds coupled with appropriate processing energy is expected to further improve the quality of processing.

Adjustable carbon fiber reinforced plastic panel for a large-aperture telescope

Segmented mirrors are commonly used to construct large-aperture telescopes. We present a methodology for structural analysis and experimental results of an adjustment of a mm- to far-IR range (10 mm to 70 μm) segmented mirror panel to correct its deviation from an optimum paraboloid of rotation. The panel is made of high-modulus carbon fiber–reinforced plastic and has a shape of a 15-deg sector with a 1207 × 390 mm2 reflecting surface area. A system of mechanically operated adjusters for correcting large-scale surface deformations is described. We used our original method to correct fabrication errors and improved the surface shape accuracy from 23.8 to 4.5 μm (RMS values). The method is based on distance-to-target-surface minimization using vector influence functions and arbitrary movements. The results of the long-term panel shape stability monitoring and the effect of cooling the panel down to 77 K are also presented.

INFLUENCE OF THE PYROLYTIC COMPACTION PROCESS ON THE PHYSICAL AND MECHANICAL PROPERTIES OF HIGH-DENSITY CARBON-CARBON COMPOSITE MATERIALS BASED ON PITCH MATRICES

The efficiency of the pyrolytic carbon compaction process by decomposing methane in samples of a carbon-carbon composite randomly reinforced with discrete high-modulus (graphitized) carbon fibers with different densities is investigated. The analysis of the test results of samples for determining the compressive strength, determining the densities of samples after compaction with pyrocarbon and after compaction by impregnation and carbonization under pressure is carried out. Scanning electron microscopy (SEM) was used to study the structure of material samples with different initial density values.

Debonding characterization for all-lightweight RC T-Beams strengthened in flexure with FRP

This paper presents an experimental, analytical and numerical comparison of the behavior of lightweight and normal weight concrete beams strengthened with externally bonded high modulus carbon fiber. The main objective of this paper is to study the efficiency of using CFRP with all-lightweight concrete beams in flexural performance and validate the use of the modification factor (λ), proposed by ACI 318-19 for various concrete parameters, in adjusting the ACI 440.2 debonding strain. An experimental program was conducted using six full-scale T-beams made of two different concrete types, normal weight concrete, and all-lightweight concrete. Each series consisted of a control beam, and two beams strengthened using either two or four layers of high modulus CFRP. The results showed that the percent increase in flexural capacity is more evident in the normal weight beams as the number of layers increases. At the same time, this increase in lightweight beams is shown to be about the same beyond the use of two layers. Moreover, the reduction factors were found to be 0.93 and 0.85 leading to accurate recovery of the debonding experimental failure using the ACI 440.2 equation for the two-layered and four-layered beams, respectively. A nonlinear analysis parametric study was conducted to examine the parameter not varied in the experiments. A comparison to the debonding strain specified by other standards and models was also performed.

Calculation of strength, rigidity, and stability of the aircraft fuselage frame made of composite materials

Carbon-carbon composite materials (CCCM) are characterized by high heat resistance and thermostability for which they, in most of their physical and mechanical characteristics, can be attributed to the most promising materials. Approximately 81% of all carbon-carbon composite materials are used for the manufacture of brake rotors for aircraft, 18% – in space rocket technology, and only 1% – for all other areas of application. This study discusses calculations of the strength, rigidity, and stability of a frame made of carbon-carbon composite materials. It is known that the strength of CCCM based on high-strength carbon fibers is higher than the strength of a composite material based on high-modulus carbon fibers obtained at various processing temperatures. The stress-strain behaviour (SSB) of the material is carried out. Among the special properties of CCCM are low porosity, low coefficient of thermal expansion, maintaining a stable structure and properties, as well as product dimensions.

Shear and Flexural Strengthening of Steel Beams with Thick Carbon Fiber Reinforced Polymer Laminate

In this paper, shear and flexural behavior of structural steel beams strengthened by high modulus carbon fiber reinforced polymer (CFRP) laminates are presented. Totally, 18 steel specimens including 6 un-strengthened beams as control specimens and 12 strengthened steel beams with simple supports were tested under 3-point bending test set-up. All specimens were strengthened using the bonded system. Influence of different parameters including length of steel beams, section size of specimens, number of CFRP laminates, and location of CFRP laminates were studied. Based on anticipated failure modes, the bonded laminates were implemented on the surface of tension flange, compression flange, and web of beams. Three failure modes of flexural, shear, and lateral-torsional buckling failures were observed in the tested beams. The main goal of these experiments was to evaluate the enhancement in load capacity, beam ductility, and initial stiffness. The results showed that the yield load, ultimate load capacity, and energy absorption of strengthened steel beams improved up to 15, 29 and 28 percent, respectively. Finally, in order to predict test results and compare the actual and predicted valves, analytical and numerical studies were carried out.

Shear behavior of RC T-beams externally strengthened with anchored high modulus carbon fiber-reinforced polymer (CFRP) laminates

This work presents the results of an experimental study on the effect of shear strengthening of reinforced concrete (RC) T-beams with high modulus carbon fiber-reinforced polymer (CFRP) laminates and anchors. The parameters considered were the anchor insertion angle and dowel diameter. Experimental results showed that the addition of U-wraps led to a 61% increase in shear strength compared to the control specimen, but failure was dominated by the brittle debonding of the CFRP laminates, with no ductility exhibited prior to failure. Anchoring the CFRP laminates with CFRP spike anchors further enhanced the shear capacity of the U-wrapped specimen by 14–51% and improved the shear contribution of the FRP by 36–136%, respectively. In addition, the CFRP anchorage system highly utilized the strain in the CFRP laminates and substantially enhanced the ductility of the specimens. A comparison between the shear resistance provided by the FRP reinforcement of the tested specimens and predicted capacity using current design guidelines showed that the current provisions could be safely applied to design RC T-beams strengthened in shear with anchored CFRP U-wraps.

Gradual failure in high-performance unidirectional thin-ply carbon/glass hybrid composites under bending

This paper introduces new composite architectures using carbon and glass fibre-reinforced epoxy prepregs to achieve gradual failure under bending. The concept is based on a technique developed by the authors to design hybrid composites with gradual failure in tension combined with beam theory to identify and control the failure sequence of the plies in the layups. Two layups are designed based on standard ply thickness S-Glass and hybrid sub-laminates made out of intermediate and high modulus thin-ply carbon prepregs. The layups are tested under 4-point bending loading where a gradual failure alongside high values of flexural displacement are achieved. No catastrophic failure is observed throughout the whole loading process. The gradual layer-by-layer failure of the surface layers on the tensile side produces a brush-like appearance. Microscopy observations from interrupted tests verified fragmentation of the high-modulus carbon layer followed by gradual failure of the intermediate modulus carbon layer and delamination on the tensile side, as well as stable shear cracks of the high-modulus carbon layer on the compression side.

Effect of Process-Induced Resin Bead on the Measured Tensile Strength of Polyacrylonitrile-Based Carbon Fibers

Abstract The aim of this work is to investigate the effect of a process-induced resin bead on the measured tensile strength of polyacrylonitrile-based carbon fibers. It is found that the resin bead was formed on the surface of carbon fiber specimens if the carbon fibers impregnated with resin were positioned horizontally during the tensile specimen preparation. Mechanical testing results indicated that the measured tensile strength of carbon fibers noticeably decreased by about 10 % due to the formation of the resin bead, and the initial fracture of carbon fibers usually occurred around the resin bead. Moreover, the bending of the filaments in the resin bead had been observed by optical microscope. It is concluded that the flowing and curing of excess resin lead to the bending of loose filaments in carbon fiber tow during specimen preparation; thus, internal stress was subsequently formed in the fiber specimen, which is detrimental to the measured tensile strength. Finally, based on the microscopic observations, theoretical analysis under the maximum stress criterion was employed to predict the tensile strength of carbon fibers with a resin bead, and the theoretical results agree well with the experimental results. It is verified that the bending angle and the fraction of the bending filaments in the resin bead play important roles in deteriorating the measured tensile strength. These conclusions can help to improve the tensile testing method for accurately measuring the tensile strength of high modulus carbon fibers.

A Study of the Thermo-Mechanical Behavior of a Gas Turbine Blade in Composite Materials Reinforced with Mast

The turbine blades are subjected to high operating temperatures and high centrifugal tensile stress due to rotational speeds. The maximum temperature at the inlet of the turbine is currently limited by the resistance of the materials used for the blades. The present paper is focused on the thermo-mechanical behavior of the blade in composite materials with reinforced mast under two different types of loading. The material studied in this work is a composite material, the selected matrix is a technical ceramic which is alumina (aluminum oxide Al2O3) and the reinforcement is carried out by short fibers of high modulus carbon to optimize a percentage of 40% carbon and 60% of ceramics. The simulation was performed numerically by Ansys (Workbench 16.0) software. The comparative analysis was conducted to determine displacements, strains and Von Mises stress of composite material and then compared to other materials such as Titanium Alloy, Stainless Steel Alloy, and Aluminum 2024 Alloy. The results were compared in order to select the material with the best performance in terms of rigidity under thermo-mechanical stresses. While comparing these materials, it is found that composite material is better suited for high temperature applications. On evaluating the graphs drawn for, strains and displacements, the blade in composite materials reinforced with mast is considered as optimum.

Effect of nickel electroplating followed by a further copper electroplating on the micro-structure and mechanical properties of high modulus carbon fibers

The nickel electroplating followed by a further copper electroplating process was conducted on high modulus carbon fibers (HMCFs), and the HMCFs were oxidized in nitric acid prior to the Ni-plating process. Effect of the electroplating process on the microstructure and mechanical properties of HMCFs was investigated. Uniform nickel particles were observed on the surfaces of Ni-plated HMCFs and fiber diameter increased from 5.0 μm to 6.1 μm. With a further Cu-electroplating process, the fiber diameter continued increasing to 7.5 μm. The Ni-plating process resulted in increased surface roughness, whereas the surface RMS and Ra values dropped significantly after the Cu-plating process. Owing to the Ni-plating treatment, the relative content of carbon element on fiber surfaces decreased from 96.54 % to 36.74 %. After a further Cu-plating process, the relative content of Cu element on HMCF surfaces was as high as 54.01 %. The electroplating process resulted in decreased tensile modulus from 415.71 GPa to 407.71 GPa. By contrast, the tensile strength of electroplated HMCFs increased by 1.1 % due to the reduction of fiber defects and stress concentration. Results also showed that both the Ni-plating and Cu-plating process could lead to significant decreases in the values of electrical resistance and resistivity.

Tension-tension fatigue behavior of hybrid glass/carbon and carbon/carbon composites

This work investigates the quasi-static, low-cycle and fatigue behavior of hybrid glass/ultra-high modulus carbon (GC) and low modulus/ /high modulus carbon (CC) fiber composites. These pseudo-ductile unidirectional interlayer hybrids are a new type of composites whose potential is not yet fully understood, particularly under cyclic/fatigue loading. Different test methods (digital image correlation, video extensometer and thermal camera) were used to record the evolution of the strain, damage and temperature during loading. The results of quasi-static loading shown pseudo-ductile responses with multiple fractures for all the series. The CC specimens exhibited higher initial elastic modulus, ‘yield’ stress and strength, while the GC specimens showed the highest pseudo-ductile strain. Much higher capacity of CC to resist to fatigue loading was observed. In the GC specimens significant damage was accumulated during fatigue loading, when the damage evolution of multiple fractures in different layers developed to delamination between the glass and carbon layers.

Promising Hybrid Fabrics Based on Carbon and Aramid Fibers as a Reinforcing Filler for Polymer Composites

The possibility of using a hybrid fabric made of a high-modulus carbon fiber ZhGV yarn and a high-strength aramid Rusar-NT yarn for reinforcing a polymer composite material is considered. The results of determining the physicomechanical characteristics of a hybrid composite material and the values of the coefficients of realization of the strength and modulus of elasticity of carbon and aramid fibers in the composition of the composite material are presented.

Tunneling cracks in arbitrary oriented off-axis lamina

The steady-state energy release rate for tunneling cracks under mixed-mode loading is determined using finite element analyses. The balanced and symmetric laminate layup $$[0/\theta /0/-\theta ]_s$$ is investigated, where the tunneling crack is located parallel to the fiber direction of the central off-axis oriented layer. It is found that for the steady-state situation, a simple energy balance calculation of the released energy of the separated crack surfaces for a fully developed crack gives the same value as the average value of a detailed J-integral analysis of the crack front. Furthermore, the crack front mode-mixity, obtained by the same energy balance calculation, was found to give a good prediction of the average mode-mixity found from a detailed stress intensity calculation along the crack-tip. Based on this simplified energy balance approach, the energy release rate is determined for all angles $$\theta \in {]}0;90]^{\circ }$$ for orthotropic elastic properties ranging from typical low modulus glass fiber reinforced polymers to high modulus carbon fiber reinforced polymers. The predicted results can be used to investigate the influence of the layup angles on static and fatigue tunnel crack evolution in composite materials used within, e.g. automotive, aerospace, and wind energy applications.

Understanding compressive strength improvement of high modulus carbon-fiber reinforced polymeric composites through fiber-matrix interface characterization

Low fiber-direction compressive strength of high-modulus (HM) carbon fiber-reinforced polymers (CFRPs) has been their major weakness prohibiting implementation of such materials in aircraft primary structures despite improving mechanical stiffness at a lower weight. A new HM CFRP achieving fiber-direction compressive strength of intermediate-modulus (IM) CFRPs but with more than 30% higher axial modulus has been recently developed. This work looks into fiber-matrix interface shear strength as a potential mechanism driving the compression strength improvement of the new material system. In-situ scanning electron microscopy (SEM) based single fiber push-out experiments addressing standing challenges associated with manufacturing high-quality samples as well as distinguishing same-diameter HM and IM carbon fibers in the hybrid composite system are used to measure fiber-matrix interface shear strength. The experiments show a 29% lower average value of the fiber-matrix interface shear strength for the HM carbon fibers compared to the IM carbon fibers in the new material system. Such a significant reduction corresponds to a 22% lower fiber-direction compressive strength of the HM CFRP without the integrated IM fibers. The results support the idea of integrating off-the-shelf IM carbon fibers with a stronger fiber-matrix interface and a higher shear modulus into HM CFRPs to improve their compressive strength.

Analytical hybrid effect prediction and evolution of the tensile response of unidirectional hybrid fibre-reinforced polymers composites for civil engineering applications

The performance of a progressive damage model in quantitative hybrid effect prediction of a comprehensive set of different 16 unidirectional interlayer (layer-by-layer) hybrid composites was assessed. Composites, produced by the hand lay-up method, made out of four different commercially available dry unidirectional fabric materials, namely high-modulus carbon, standard carbon, E-glass and basalt, were tested. Tensile tests on single fibres were performed in order to determine their Weibull strength distribution parameters, which were used as inputs of the progressive damage model. Reasonably good agreement between analytical and experimental hybrid effect results was obtained, which allowed to estimate satisfactorily the reference strengths of the unidirectional low strain composite materials. Next, an existing analytical model for the simulation of stress–strain curve of hybrid composites was adapted to contemplate the hybrid effect, which allowed to predict the following properties of unidirectional hybrid combinations: ‘yield’ stress (or pseudo-yield stress), pseudo-ductile strain and strength. It was verified as well that predictions of the three properties referred to were in close agreement with the test results. Finally, damage mode maps were used in the analysis of these properties and, furthermore, of the hybrid effect and the elastic modulus of hybrid combinations.

High Young's modulus carbon fibers are fouling resistant with fast-scan cyclic voltammetry.

We report evidence that high Young's modulus carbon-fibers resist detrimental chemical fouling at their surface similarly to carbon nanotube fibers with fast-scan cyclic voltammetry. This provides a new method for stable monitoring of neurochemicals like serotonin, without the need to purchase costly carbon nanotube microfibers or perform complicated electrode immobilizations.

Fatigue Behavior of Unidirectional High Modulus Carbon Fiber Reinforced Plastics

Fatigue Behavior of Unidirectional High Modulus Carbon Fiber Reinforced Plastics

Enhancing the interfacial properties of high-modulus carbon fiber reinforced polymer matrix composites via electrochemical surface oxidation and grafting

Surface modification of carbon fiber is a traditional research field and many techniques have been developed to improve the adhesion force between fiber and the polymer matrix. However, most studies were focused on the carbon fibers with standard modulus. The surface of high-modulus carbon fiber (HMCF) is difficult to be activated due to the highly inert structure after graphitization. A convenient and effective surface modification method that can simultaneously improve the content of function groups with containing oxygen and nitrogen on the surface of HMCF was developed in this paper. The surface of HMCF was first anodized to be activated by electrochemical oxidation, and then the diethylenetriamine (DETA) was grafted by electrochemical grafting. The effect of the type of electrolyte on the electrochemical grafting of DETA was studied by the addition of NH4HCO3 and (NH4)2SO4, respectively. The results indicated that the addition of NH4HCO3 electrolyte in DETA solution will promote the grafting and increase the grafted amount on HMCF surface. Moreover, the addition of (NH4)2SO4 electrolyte can not only promote the grafting, but also oxidize the surface of the fibers further to generate more oxygen-containing groups. In addition, the interfacial performance of HMCF composites was significantly improved after modification by this method. Especially, when (NH4)2SO4 was added to DETA solution, the inter-laminar shear strength (ILSS) of HMCF/epoxy composites reached 97.5 MPa, which was 257.1% higher than that of untreated HMCF.