High Modulus Carbon Fibers Research Articles

補強量の違いが耐爆補強効果に及ぼす影響

When designing blast-resistant reinforced concrete (RC) structures, it is important to reduce spall damage due to reflected tensile stress waves. In this study, to devise a blast-resistant strengthening method for existing RC slabs, contact detonation tests using 200 g of explosive charges were conducted on RC slabs with rear surfaces strengthened with continuous fiber sheets/meshes. High-strength carbon fiber (HSCF) and high-modulus carbon fiber (HMCF) sheets were employed to strengthen 75-mm-thick RC slabs, and the number of layers used for strengthening them was varied between 2, 4, and 6 layers. Two types of carbon fiber reinforced plastic (CFRP) meshes, in which the weight per unit area of carbon fibers was varied between 215 and 430 g/m2, were also used to strengthen 100-mm-thick RC slabs. The results showed that the spall failure of the 75-mm-thick RC slabs could be prevented by bonding more than four HSCF sheets onto the rear side of the slab; however, the HMCF sheets had no effect on the blast resistance of the slabs because of fiber rupture. Further, the spall failure of the 100-mm-thick RC slabs could be prevented by bonding the CFRP meshes with fibers 430 g/m2 in volume. On the basis of the test results, the criteria for fiber rupture in CF sheets due to detonation loading was discussed in terms of the fracture energy of the sheets and the modified-scaled concrete thickness of the slab. Furthermore, high-speed photography was employed to investigate the spall failure process of each strengthened slab.

Modulus Effect of Bonded CFRP Laminates Used for Repairing Preyield and Postyield Cracked Concrete Beams

AbstractTwo different prerepair loading histories were simulated in 3,000×300×150 mm reinforced concrete beams, namely cracking within the elastic range, and overloading in the plastic range. After unloading, the beams were repaired with either high or ultrahigh modulus (210 or 400 GPa) carbon fiber–reinforced polymer (CFRP) plates, or a hybrid system, and then reloaded to failure. It was shown that the level of preexisting damage has insignificant effect on strengthening effectiveness and failure mode at ultimate. The 210 and 400 GPa CFRP of reinforcement ratio ρf=0.17% increased the yielding load by 33 and 60%, respectively, whereas the ultimate strength was increased by up to 29 and 51%, respectively. Doubling ρf of the 400 GPa CFRP to 0.34% resulted in a 63% overall gain in flexural strength, which is only an 8% increase over ρf=0.17%, because of change in failure mode from rupture to concrete cover delamination. The beam retrofitted by hybrid CFRP showed remarkable pseudoductility and warning signs....

Radiation curing of carbon fibre composites

Epoxy/carbon fibre reinforced composites were produced by means of e-beam irradiation through a pulsed 10MeV electron beam accelerator. The matrix consisted of a difunctional epoxy monomer (DGEBA) and an initiator of cationic polymerisation, while the reinforcement was a unidirectional high modulus carbon fibre fabric. Dynamic mechanical thermal analysis was carried out in order to determine the cross-linking degree. The analysis pointed out a nonuniformity in the cross-linking degree of the e-beam cured panels, with the formation of clusters at low Tg (glass transition temperature) and clusters at high Tg. An out-of-mould post irradiation thermal treatment on e-beam cured samples provides a higher uniformity in the network although some slight degradation effects. Mode I delamination fracture toughness and Interlaminar Shear Strength (ISS) were also investigated by means of Double Cantilever Beam (DCB) and Short Beam Shear tests, respectively. Results from this mechanical characterisation allowed to correlate fracture toughness of the bulk matrix resin, cross-linking density and fibre/matrix interaction to the delamination fracture behaviour of the fibre reinforced material.

Fatigue tests on steel plates with longitudinal weld attachment strengthened by ultra high modulus carbon fibre reinforced polymer plate

ABSTRACTWelded steel connections of infrastructures are susceptible to fatigue failure. Advanced carbon fibre reinforced polymer (CFRP) has been demonstrated promising for fatigue strengthening of steel structures. Limited research was conducted on CFRP strengthening of welded connections. This paper focuses on the application of ultra high modulus (UHM) CFRP plates with a modulus of 460 GPa to strengthen steel plates with longitudinal fillet weld attachment using five CFRP strengthening configurations. A series of fatigue tension tests were carried out with constant amplitude fatigue loading. Beach marking technique was adopted to record the crack propagation process. Effects of CFRP bond length, bond width and bond locations on fatigue performance of welded steel joints were investigated. The experimental results showed that UHM CFRP plates could generally increase the fatigue life of the welded steel joints. It seems better to apply CFRP on the welding side of the specimen to achieve longer fatigue life. Then, the effects of weld and weld attachment on the CFRP strengthening efficiency was further studied by comparing experimental results of non‐welded steel plates with single side UHM CFRP plate strengthening. Finally, the classification method was adopted to assess the strengthening efficiency of the UHM CFRP plate to the steel plates with longitudinal weld attachment.

CARBON NANOTUBES AND SHORT HIGH MODULUS CARBON FIBRES COMBINATION TO COMPOSITE PREPARATION

The improvement of the thermal properties of high conductive metal matrix composites is expected with suitable coefficient of thermal expansion CTE by using short carbon fibres Granoc XN-100 having axial thermal conductivity of 9 00 W/m.K upon its combination with carbon nanotubes (CNTs). From this reason a parametric study of the synthesis of multi wall carbon nanotubes (MWCNTs) by catalytic decomposition of acetylene over catalyst precursor based on nanometer sized hematite particles was performed. The nanoparticles were applied on the surface of commercial short high modulus (HM) carbon Granoc XN-100 fibres and MWCNTs were grown by catalytic chemical vapour deposition (CCVD) method. SEM and TEM images showed that multi wall CNTs was prepared but coaxial cylindrical graphene sheets and bamboo like microstructure was observed. The variation the CNTs synthesis parameters e.g. reaction time and surface covering density of hematite catalyst on HM carbon fibres resulted in production of desired quantity and quality of CNTs.

Electron microscopy investigation of interface between carbon fiber and ultra high molecular weight polyethylene

Scanning electron microscopy was used to investigate the surface of initial and modified high-strength and high-modulus carbon fibers as well as interfaces in the ultra high molecular weight polyethylene, filled with above-mentioned fibers. Effect of the fibers surface modifying method on the adhesive interactions in composites was studied. It was observed that interaction of matrix with a modified surface of fibers results in a formation of bonds with strength higher than the yield strength of the polymer. It results in a formation of long nanosized polymer wires at tensile fracture of composites.

The Effect of Abrasion Surface Treatment on the Bonding Behavior of Various Carbon Fiber-Reinforced Composites

In this paper we show that current abrasion surface preparation practices do not perform equally on all composite surfaces. The effect of abrasion on the adhesive bond strength of various carbon fiber (CF) composites was investigated. Cyanate ester composites were fabricated using a low, a high and an ultra high modulus carbon fiber (T300, M55J, K13C2U). XPS and contact angle measurements showed that the surface energy of all three composites increased due to the removal of contaminants as well as increased in surface roughness. However, the lap shear strength degraded sharply for a number of cases, irrespective of roughness, depending on the fiber used. Composites utilizing lower modulus carbon fibers increased in adhesive bond strength following abrasion in comparison to composites with higher modulus fibers. As the modulus of the fiber and the abrasive grit size increased, the degree of degradation caused by abrasion was shown to increase significantly. Scanning electron microscopy (SEM) and profilometry measurements showed the development of an abrasion-affected zone that was especially prevalent for higher stiffness composites. The failures for the higher modulus specimens were caused by subsurface damage located a few fiber diameters below the abraded surface. However, an alternate technique using atmospheric plasma surface treatment exhibited efficient removal of contaminants while showing no degradation of bond quality when treating these ultra high modulus composites.

Investigation of the long term effects of moisture on carbon fibre and epoxy matrix composites

The aim of this work is to investigate the long term effects of moisture on the interface between a carbon fibre and an epoxy matrix. High modulus carbon fibres were used to prepare single fibre model composites based on an epoxy resin. The samples were immersed in the seawater and demineralised water and their moisture uptake behaviour was monitored. The equilibrium moisture content and diffusion coefficients for the samples were determined. DSC has been used to analyse the moisture effects on glass transition temperature and thermal stability of the pure epoxy specimens. These results showed a reduction in the glass transition temperature (Tg) after moisture absorption. Tensile tests were also carried out for the epoxy specimens and a general decrease in the mechanical properties of the epoxy matrix was observed. Raman spectroscopy was used to observe the effects of moisture on the axial strain of the carbon fibre within the composite and stress transfer at the interface as a function of exposure time. The results show that the decrease in the mechanical and interfacial properties of the model composites under the seawater immersion is more significant than under demineralised water immersion.

Fatigue Properties of the Cell 3D Composite Structure

A novel type of hybrid cell composite structure has been developed, experimentally investigated and used for many practical applications. The cell system can fill relatively thick parts of cross sections of beams with lower risk of shear stress damage and cracks between uniaxial oriented fibres. Typical macroscopic sub-cells in the cross section structure are formed by the stamping process of partially cured and axially-oriented high modulus carbon fibre bundles (about 4-6 mm in the diameter), which are wrapped around by a thin layer of high strength fibres (oriented in ±45 or 89 degrees). An advantage of this final 3D cell composite structure is its higher static and fatigue strength and shear stiffness in comparison with thick unidirectional composite parts. Static, fatigue and residual static strength was experimentally investigated for 1D unidirectional as well as for 3D cell structure under four point bending loading on specimens with the rectangular cross section. The 3D structure shows much better static and fatigue properties as the thick 1D unidirectional structure.

Study on Thermal Dilation Coefficient of Fiber Concrete at early Stage

The addition of fiber into concrete can not only suppress the interior shrinkage strain and decrease the thermal dilation coefficient (TDC) of concrete, but also it can lessen the width of shrinkage crack, especially reduce the appearance of interconnected pore, thus the reduction of the water content of capillary pore will make the TDC of paste matrix lessen. In this paper, an experiment was designed to study the TDC from the 5th day to the 29th day after the concrete was poured. The results show that the addition of fiber can effectively reduce the TDC of concrete. When the addition is the same, high-modulus carbon fiber reinforced concrete has a lower TDC than low-modulus polyester fiber concrete.

Structural features of polyacrylonitrile-based carbon fibers

The structural changes as functions of spinning conditions and heat treatments were investigated with respect to the structural feature of PAN-based carbon fibers by scanning tunneling microscopy (STM). The distinct granule structure on the cross section of both high tensile strength and high modulus carbon fibers was observed by SEM, while slender granule-shape domain on the longitudinal surface was revealed by STM. A structure model was proposed, which depicted that the PAN-based carbon fiber was a heterogeneous structure composed of aggregated mesostructural domains. These domains were closely arranged into spiral form along fiber axis, allowing the fibers have high strength and good elongation. The initial shape and size of domains was determined by the precursor composition and spinning conditions and also strongly depended on the heat-treated temperature and stretching conditions. The smaller or slender domain, the higher tensile strength obtained for fibers. We expect that the PAN-based carbon fiber with better performance should be produced by optimizing the size and shape of these domains.

Preparation of Polyacrylonitrile High Modulus Carbon Fibers by Catalytic Graphitization Using Boron

Catalytic graphitization of polyacrylonitrile-based carbon fiber by doping boric acid was reported in this paper. The microstructure and mechanical properties of polyacrylonitrile-based carbon fibers with and without doping boric acid after heat treatment of 1300°C,1500°C,1800°C, 2100°C,2300°C,2400°Cand 2500°Cwas investigated by X-ray diffraction (XRD) and mechanical testing. The results showed that the tensile modulus of the carbon fibers either boron modified or not, increased obviously with increasing temperatures, and that of the modified carbon fibers was much higher than the unmodified fibers at all temperatures, reaching 404Gpa when the fiber was graphitized at 2500°C. The tensile strength of the modified carbon fibers was lower than the unmodified ones after being graphitized at temperatures below 2300°C, but increased to 2.69 GPa and 2.46 GPa respectively after the fibers were treated at 2300°C and 2500°C, which were higher than that of unmodified fibers treated under the same conditions, indicatinging that the mechanism of boron catalytic graphitization changed at the temperatures higher than 2300°C. It also showed that the interlayer spacing (d002) decreased, while the crystallite size (Lc) and the orientation increased with increasing temperatures.

Latent Curing Agent Modified Epoxy Sizing Agent for High Modulus Carbon Fiber

A new kind of latent curing agent (LCA) for epoxy resin was synthesized to improve the properties of epoxy sizing agent for high modulus carbon fiber by the reaction of ethylenediamine with butylacrylate in equal molar ratios, and the chemical structure and thermal property of the LCA were studied with FTIR and TGA, respectively. Moreover, LCA modified epoxy resin used as sizing agent for high modulus carbon fiber was studied. The results show that the wettability of sized high modulus carbon fiber tends to increase due to the increase of LCA content in sizing agent on the surface of the carbon fiber; while absorbability of sized high modulus carbon fiber tends to decrease; and drape of the sized high modulus carbon fiber which indicates the shaping effect of the fiber changes with the content of LCA, and interlaminar shear strength (ILSS) of the sized high modulus carbon fiber/epoxy composites is improved to 78MPa, which increased by 8.6% compared with the composites reinforced by high modulus carbon fiber with unmodified sizing agent, indicating that using LCA modified epoxy resin as sizing agent for high modulus carbon fiber is a feasible method to improve the interfacial performance of high modulus carbon fiber/epoxy composites.

Study of the Surface Morphology and the Microstructure of PAN-Based Carbon Fibers

The microstructure of two kinds of self-made PAN-based high-modulus carbon fibers (HMCF-1, HMCF-2) was studied by scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM), and was compared with that of T800 and M55J. The correlation of XRD and HRTEM in terms of graphite crystallite sizes and interlayer spacing of graphite layer was also investigated. The results show that the diameters of T800, HMCF-1 and HMCF-2 are almost the same (~5.20μm) and all of them are lager than that of M55J (~4.86μm). The crystal sizes and the degree of graphitization are in the order of HMCF-2>HMCF-1>M55J>T800, while the regularity of the lattice fringes of HMCF-2 is better than those of others.

Effect of vacuum thermal cyclic exposures on unidirectional carbon fiber/epoxy composites for low earth orbit space applications

The effects of the low earth orbit environment on three types of unidirectional high-modulus carbon fiber (M40J, M55J and M60J)-reinforced composites were determined in detail. The synergistic environmental factors were the vacuum environment and thermal cycling. Cyclic thermal loading was performed in the temperature range between 120°C and −175°C for up to 2000cycles under the high-vacuum state of 1.3−3Pa. The material responses were characterized through an assessment of the physical, thermal and mechanical property changes. It follows from the experimental results presented that the synergistic actions of the vacuum and the thermal cycling on the composite property degradation can be attributed to the formation of microvoids and interfacial sliding at the fiber–matrix interface in the early stages of cycling. The implications of these degradation processes based on the dependence of composite properties on vacuum thermal cycling are also discussed.

Epoxy Modified Polyurethanes Coated High Modulus Carbon Fiber: Synthesis and Properties Studies

With toluene 2, 4-diisocyanate (TDI), polyethylene glycol (PEG) and 2,3-Epoxy-1-prop -anol (glycidol) used as the raw materials, two epoxy terminated polyurethanes (EPU) was synthesized by prepolymerization and closed end. Moreover, EPU with high toughhess is chosen as a coating agent for carbon fiber with three ethylene tetramine (TETA) as curing agen. The influence of the content of crosslinking agent in the coating layer on properties of composites and the mechanism of interface toughness are investigated. The chemical structure and thermal property of the EPU were studied with FTIR, 1HNMR and TGA, respectively. It proves that the thermal stability of EPU is more stable than epoxy coating. The interlaminar shear strength (ILSS) of the sized high modulus carbon fiber/epoxy composites is improved to 71MPa, which increased by 19.4% compared with the composites reinforced by unsized high modulus carbon fiber, and DMTA show that using EPU as a new kind of polymer coating for carbon fiber is a feasible method to improve the interfacial performance of high modulus carbon fiber/epoxy composites.

Heat durability of carbon fiber reinforced nickel composites

Carbon fiber is a highly heat resistive material in an oxygen free atmosphere. Nickel is also a heat resistive metal and an important element for a superalloy. We can expect an excellent heat durable composite when they are combined. Nickel was electroplated on a carbon yarn to form a monofilament composite. When the high strength fiber was tested, the composite started to lose its strength at 600°C. The deterioration was caused by graphitization of the carbon in the fiber. This is caused by the difference of the graphitization degree between crystallites in a fiber. A high modulus carbon fiber has little difference of the graphitization degree in a fiber. The high modulus fiber did not react when tested and the fiber strength was maintained after heat treatment at 1100°C for 9 h. From the results, the high modulus carbon fiber composite is promising to be durable at a high temperature.

Hybrid effect on mechanical properties of M40‐T300 carbon fiber reinforced Bisphenol A Dicyanate ester composites

AbstractInterply and intraply hybrid composites based on Bisphenol A Dicyanate ester (BADCy), high strength carbon fibers T300, and high modulus carbon fibers M40 were prepared by monofilament dip‐winding and press molding technique. The tensile, flexural, interlaminar shear properties and SEM analysis of the hybrid composites with different fiber content and fiber arrangement were investigated. The results indicated that the mechanical properties of intraply hybrid composites were mainly determined by fiber volume contents. When the ratio of fiber volume content was close to 1:1, the intraply hybrid composites possessed lowest tensile and flexural strength. The mechanical properties of interply hybrid composite mainly depended on the fiber arrangement, instead of the fiber volume contents. The hybrid composites using T300 fiber layout as outside layer possessed high flexural strength and low flexural modulus, which was close to that of T300/BADCy composites. The hybrid composites ([(M40)x/(T300)y]S) using M40 fiber layout as outside layer and T300 fibers in the mid‐plane had high flexural modulus and interlaminar shear strength. POLYM. COMPOS., 2010. © 2010 Society of Plastics Engineers

Synthesis of Latent Curing Agent for Epoxy Resin

A new kind of latent curing agent (LCA) for epoxy resin was synthesized by the reaction of Ethylenediamine with Butylacrylate in equal molar ratios, and the chemical structure and thermal property of the LCA were studied with FTIR and TGA, respectively. Moreover, LCA was also used to modify the epoxy sizing agent for high modulus carbon fiber. The results show that the wettability of sized carbon fiber tends to increase due to the increase of the polymer film on the surface of the carbon fiber, and interlaminar shear strength (ILSS) of the sized high modulus carbon fiber/epoxy composites is improved to 78MPa, which is increased by 8.6% compared with the composites reinforced by high modulus carbon fiber with unmodified sizing agent, indicating that using LCA modified epoxy resin as polymer coating for carbon fiber is a feasible method to improve the interfacial performance of high modulus carbon fiber/epoxy composites.

Development of High Modulus/High Strength Carbon Fiber Reinforced Nanoparticle Filled Polyimide Based Multiscale Hybrid Composites

The polyacrylonitrile (PAN)-based and pitch-based carbon fiber-reinforced nanoparticle filled polyimide based multiscale hybrid composites have been fabricated using vacuum assisted resin transfer molding (VaRTM) and autoclave curing. The carbon fibers used in this study were high tensile strength PAN-based (T1000GB) and high modulus pitch-based (K13D) carbon fibers. Fiber orientations of the T1000GB/K13D hybrid composites were set to [0(T1000GB)/0(K13D)]2S (T1000GB and K13D unidirectional layers were alternately and symmetrically laminated). The fiber volume fraction was 50 vol% (T1000GB: 24.9 vol%, K13D: 25.1 vol%). Polyimide used in this study was a commercially available polyimide precursor solution (Skybond 703). Four different types of nanoparticle (25nm-C, 20-30nm-β-SiC, 130nm-β-SiC and 80nm-SiO2) and particle volume fraction was 5.0 vol% used for the inclusion. The tensile properties and fracture behavior of T1000GB/K13D nanoparticle filled and unfilled hybrid composites have been investigated. For 25nm-C, 20-30nm-β-SiC and 80nm-SiO2 nanoparticle filled and unfilled hybrid composites, the tensile stress-strain curves show a complicated shape. By the high modulus pitch-based carbon fiber, the hybrid composites show the high modulus in the initial stage of loading. Subsequently, when the high modulus carbon fiber begin to fail, the high strength fiber would hold the load (strength) and the material continues to endure high load without instantaneous failure.