T700 Carbon Fiber Research Articles

Flexural Properties of T700 2D C<sub>f</sub>/SiC Composites via Precursor Infiltration and Pyrolysis

2D Cf/SiC composites were prepared by precursor infiltration and pyrolysis (PIP) process with spreaded T700-12K plain weave carbon clothes as the reinforcement. The mechanical properties and microstructures were investigated. The composites are compact with few internal defects since the precursor could infiltrate the preform effectively. CVD-PyC interface modified the surface of T700 carbon fiber, a rough surface is helpful for the interfacial combination and the load transfer. For the Cf/PyC/SiC composites, the flexural strength and flexural modulus were 425±23.2 MPa and 36.3±3.1 GPa, respectively.

The fiber volume fraction influence on mechanical properties of multi-layered carbon tubes

This paper considers development and analysis of the mechanical behaviour of tubes which are made of composite materials under loading. Composite materials interface between layers have an essential influence on mechanical characteristics and are hardly predictable be-fore combining this mix. Presented analysis focuses on tubes, made of unidirectional carbon fiber, epoxy resin, considering various structure combinations and influence on mechanical behaviour under critical circumstances. The specimen tubes were reinforced using the polyacrylonitrile-based Toray T700 carbon fiber tow, of intermediate strength and modulus, combined with epoxy resin matrix of different impregnation, in order to analyse these variations effect on stiffness and bending strength characteristics. DOI: http://dx.doi.org/10.5755/j01.mech.20.6.8880

Life Prediction on a T700 Carbon Fiber Reinforced Cylinder with Limited Accelerated Life Testing Data

An accelerated life testing investigation was conducted on a composite cylinder that consists of aluminum alloy and T700 carbon fiber. The ultimate failure stress predictions of cylinders were obtained by the mixing rule and verified by the blasting static pressure method. Based on the stress prediction of cylinder under working conditions, the constant stress accelerated life test of the cylinder was designed. However, the failure data cannot be sufficiently obtained by the accelerated life test due to the time limitation. Therefore, most of the data presented to be high censored in high stress level and zero-failure data in low stress level. When using the traditional method for rupture life prediction, the results showed to be of lower confidence. In this study, the consistency of failure mechanism for carbon fiber and cylinder was analyzed firstly. According to the analysis result, the statistical test information of carbon fiber could be utilized for the accelerated model constitution. Then, rupture life prediction method for cylinder was proposed based on the accelerated life test data and carbon fiber test data. In this way, the life prediction accuracy of cylinder could be improved obviously, and the results showed that the accuracy of this method increased by 35%.

The size dependence of tensile strength for brittle isotropic materials and carbon fiber composite materials

The size scaling of strength is examined for isotropic materials and for aligned fiber composite materials. The theoretical work follows the Weibull chain of links probabilistic form for the one dimensional cases. The three dimensional, brittle isotropic material theoretical result combines the Weibull chain of links form with a fracture mechanics requirement. The verification procedure involves single T300 carbon fiber testing at different fiber lengths. The aligned fiber strand testing is for standard T300/epoxy composites at different lengths. The theoretical predictions for the size dependence of tensile strength are in reasonable agreement with the testing results.

Low velocity impact properties of carbon nanofibers integrated carbon fiber/epoxy hybrid composites manufactured by OOA–VBO process

A nano-modified prepreg system was fabricated by impregnating T-300 carbon fiber with 1wt.% oxidized carbon nanofibers (O-CNFs) modified EPON 862 epoxy resin system. The O-CNFs modified carbon fiber reinforced polymer (CFRP) prepregs were then molded and cured into CFRP laminates via an Out of Autoclave and Vacuum Bag Only (OOA–VBO) process. Samples of 100×100mm were subjected to low velocity impact test using an instrumented falling weight impact machine at three different energy levels of 10, 20 and 30J. Fracture surface analysis and projected damage area after low velocity impact test were evaluated by scanning electron microscopy and ultrasonic C-scan, respectively. Experimental analysis indicates that the incorporation of O-CNFs into carbon fiber/epoxy laminates has improved impact resistance in terms of enhanced peak load, damage initiation energy and reduced damage area in comparison to control laminates. However, the ductility index was found to be decreased with the increase of O-CNFs loading. Micrographs revealed uniform dispersion of O-CNFs in epoxy, good adhesion between O-CNFs and epoxy polymer, and improved interfacial bonding between fiber/matrix that lead to the stronger shift of the impact resistance of the hybrid composites.

Identification of the mechanical properties of the carbon fiber and the interphase region based on computational micromechanics and Kriging metamodel

Computational micromechanics has been widely used to predict the mechanical properties of fiber reinforced composite. The accuracy of the prediction depends largely on the precise definition of the mechanical parameters of the constituents, the fiber, the matrix and the interphase, which has been increasingly recognized as a transition region between the fiber and the matrix. The mechanical properties of the matrix and the axial modulus of the carbon fiber can be measured directly. However, the interphase effect and other properties of the carbon fiber are difficult to be obtained through experimental methods. This paper deals with the parameter identification of the mechanical properties of the T300 carbon fiber and the interphase region by means of numerical methods. Firstly, a microstructure based three-phase finite element model in which interphase region has been simulated by cohesive elements was developed to predict the elastic properties of the unidirectional carbon fiber reinforced composite. By combining the finite element model with the Latin Hypercube Sampling method, metamodels based on Kriging method were then developed to explicitly parameterize the relationship between the elastic properties of the composite and the input parameters. The mechanical properties of the T300 carbon fiber and the interphase region of the studied composite were finally obtained by an inverse parameter identification procedure based on the constructed Kriging metamodel and the tested mechanical properties of the composite. Benefiting from the proposed procedure, more reliable input parameters were extracted for the T300 carbon fiber and the interphase modeling, resulting in more precise prediction of the elastic properties of the carbon fiber reinforced composites through finite element simulation.

In-plane shear investigation of biaxial carbon non-crimp fabrics with experimental tests and finite element modeling

In-plane shear is one of the basic deformation mechanisms in forming fabrics on complicated shapes. In this paper, the in-plane shear behavior of non-crimp fabrics (NCFs), including NCFs based on T300 carbon fibers with chain or tricot-chain stitches, was characterized by picture frame and bias extension tests. It was found that the stitching yarns’ strained condition depending on loading direction influences the shear behavior of NCFs. Further, the results of these two tests were compared by normalizing the shear force. It was observed that the normalized results of these two tests for shear force are consistent with each other in the direction of shear of the stitching, while deviations in other directions are attributed to the different strain mechanisms, as a result of the clamping way of the sample in the test. Finally, a mesoscopic finite element (FE) model was established to simulate the picture frame and bias extension tests for the selected T300 NCF with chain stitches. The model’s validity was checked by comparing the simulated results with the experimental ones. Although some improvements are still needed, the model provides encouraging results and good foundations to predict the shear behavior for NCFs’ forming.

Development of cross-anchored dual-core self-centering braces for seismic resistance

The steel dual-core self-centering brace (SCB) is an innovative structural member that provides both energy dissipation and re-centering properties to structures, reducing the residual drift of braced structures in earthquakes. The axial deformation capacity of the brace is doubled by using two inner cores and one outer box and by serial axial deformations of two sets of parallel tensioning elements. The original dual-core SCB that used E-glass fiber tendons or T-700 carbon fiber tendons as tensioning elements exhibited good self-centering and energy dissipation up to an interstory drift of 2.5%. The new cross-anchored dual-core SCB halves the work required to apply the initial post-tensioning forces to tendons. The potential use of high-strength steel tendons as tensioning elements is studied herein, and the effects of the number of cycles on the brace behavior, energy dissipation, and durability of the steel tendon-anchorage system are also examined. First, the mechanics and cyclic behavior of the new brace are explained; a 7950mm-long cross-anchored dual-core SCB is then tested six times. The cross-anchored dual-core SCB exhibits excellent self-centering property up to a drift of 2.5% and a maximum axial load of 1700kN. No damage to the steel tendons, anchors or bracing members is found after three cyclic loading tests with increasing displacement amplitudes and 60 low-cycle fatigue tests. Finite element analysis further confirms the hysteretic responses and mechanics of the cross-anchored dual-core SCB in the cyclic test.

Self-healable interfaces based on thermo-reversible Diels–Alder reactions in carbon fiber reinforced composites

Thermo-reversible Diels–Alder (DA) bonds formed between maleimide and furan groups have been used to generate an interphase between carbon fiber surface and an epoxy matrix leading to the ability of interfacial self-healing in carbon:epoxy composite materials. The maleimide groups were grafted on an untreated T700 carbon fiber from a three step surface treatment: (i) nitric acid oxidization, (ii) tetraethylenepentamine amination, and (iii) bismaleimide grafting. The furan groups were introduced in the reactive epoxy system from furfuryl glycidyl ether. The interface between untreated carbon fiber and epoxy matrix was considered as a reference. The interfacial shear strength (IFSS) was evaluated by single fiber micro-debonding test. The debonding force was shown to have a linear dependence with embedded length. The highest healing efficiency calculated from the debonding force was found to be about 82% more compared to the value for the reference interface. All the interphases designed with reversible DA bonds have a repeatable self-healing ability. As after the fourth healing, they can recover a relatively high healing efficiency (58% for the interphase formed by T700-BMI which is oxidized for 60min during the first treatment step).

Nano structural analysis on stiffening phenomena of PAN-based carbon fibers during tensile deformation

The effects of inner microstructures, including crystallite size, orientation and defects on the stiffening phenomena of PAN-based T300 carbon fibers under tension were explored. Single-fiber tensile test was conducted on three types of fiber: as received, 1400 and 1600°C heat treated. The distribution of crystallite orientation in a fiber from core to skin was obtained by using transmission electron microscopy. The observations indicate the load-transfer between crystallites depends on the crystallite entanglement. The slide-lock of the entangled junctions among the loosely compacted crystallites is responsible for the increasing elastic modulus during tension. The sharp drop of tensile strength (−36%) of the fiber after heat treated at 1600°C was attributed to the increasing of crystallite size, nano-pore defects and a higher misalignment of crystallites in the core region.

Healing Carbon Fiber/Polymer Interface by Resistive Heating

Interface is the key region which determines, to a great extent, the set of properties of all heterogeneous systems, including composite materials. We reported interface healing of carbon fiber reinforced thermoplastic composite material via resistive heating. The carbon fiber, T700 carbon fiber, with a resistivity of 1.66 × 103 Ω·cm was used as the heating element while the matrix is polyarylether sulfone with cardo. Micro-droplet experiment was used to study the interface strength before and after heating to determine the healing efficiency. The measurement shows (experimental results show) that resistive heating is an efficient way to heal cracks near interface.

Feasibility Study for Small Scaling Flywheel-Energy-Storage Systems in Energy Harvesting Systems

AbstractTwo concepts of scaled micro-flywheel-energy-storage systems (FESSs): a flat disk-shaped and a thin ring-shaped (outer diameter equal to height) flywheel rotors were examined in this study, focusing on material selection, energy content, losses due to air friction and motor loss. For the disk-shape micro-FESS, isotropic materials like titanium, aluminum, steel and wolfram are shown to be suitable as a flywheel rotor. Wound fiber reinforced composite plastics (T1000-, T300-carbon fibers and carbon nanotubes “CNTs”) were investigated for the flywheel in a ring shape. It was shown that isotropic materials reach the highest energy densities in the shape of a Laval disk with a rim. A micro-FESS with wolfram flywheel would reach the highest half-time-periods due to its high density, and thus, it is the favored material to design a flat disk-shaped micro-FESS with low standby-losses. Fiber reinforced plastic flywheels in ring shape reach the highest energy densities, from 150 W h/kg (T300) to 2,600 W h/kg (CNT), but display higher standby-losses as well. A scaling of the rotors was done within this study and showed that air friction is influenced by the shape of the examined flywheel rotors and the material. A linear correlation of down scaling and air friction losses was shown. As a motor/generator type, an ironless air coil Halbach array motor was suggested. Motor losses due to eddy currents in the stator coil were estimated. Losses correlated in square with downscaling. FESSs with wolfram and CNT showed the lowest standby-losses due to eddy currents.

Characterisation of fiber failure mode in T-700 carbon fiber reinforced epoxy composites by acoustic emission testing

Acoustic emissions generated by a structure under stressed condition provide an insight in to the dynamic behaviour of flaws in the structure for characterization of failure modes. Fiber failure mechanism in T-700 carbon epoxy composites is characterized by testing unidirectional specimens in longitudinal mode. Acoustic emission parameters like amplitude, energy, duration, and signal strength have been recorded and studied with respect to the applied load to assess the fiber failure characteristics. The AE data is analyzed with different correlation plots for visual pattern recognition. Significant fiber breakage is observed at above 70% of the load. Bi-linear trend of the cumulative amplitude distribution curve indicates distinctively matrix and fiber failures. Matrix cracking failure mechanism dominated the entire loading cycle and is represented by AE hits of up to 85 to 90 dB amplitude and the peak amplitude distribution is 58 to 75 dB. The wave forms of matrix cracking hits with less than 90 dB and 100 units of energy are having up to 273 kHz frequency with a peak around 100 kHz. The wave forms of fiber breakage hits with more than 90 dB and 100 units of energy have up to 448 kHz frequency and with a peak from 168 to 437 kHz. From the low amplitude filtering technique the border line for fiber breakage is observed from 89 to 92 dB.

Study of Surface Characteristics of T700 Carbon Fibers and Interfacial Properties of their Reinforced Epoxy Composites

The purpose of this paper is to comparatively study the surface characteristics of domestic and Toray T700 carbon fibers (T700-CFs) and the interfacial properties of their reinforced epoxy composites. The surface roughness and surface energy of the fibers were characterized by scanning electron microscope (SEM) and dynamic contact angle analysis (DCAA). The surface chemistry analysis of the fibers was carried out by using X-ray photoelectron spectroscopy (XPS). The interfacial properties of the T700-CF/epoxy composites were studied by testing the interlaminar shear strength (ILSS), observing SEM images of composites profiles and calculating the interfacial adhesion factors from dynamic mechanical thermal analysis (DMTA) data. The results show that domestic T700-CFs have a better interfacial adhesion to epoxy matrix due to its higher surface roughness, chemical activity and surface energy than Toray T700-CFs.

A Pre-Stitching Method to Manufacture Z-Pins Reinforced Woven Ceramic Matrix Composite Laminates

Z-pins reinforced 2D ceramic matrix composites (CMCs), integratedly designed new materials, are developed to enhance 2D CMCs through-thickness in the form of Z-pins and to ensure significant increase in interlaminar fracture toughness, delamination resistance and impact resistance, and Z-pins reinforced 2D CMCs have much application. A manual pre-stitching method is developed to make holes in the graphite fixture to control Z-pins row spacings and to introduce yarns of 3000 T300 carbon fibers bundle into a preform. Z-pins reinforced woven CMCs for research were manufactured successfully by repeatedly using chemical vapor infiltration (CVI) to infiltrate SiC matrix into woven preform and carbon fiber sutures. It is shown that this method of manufactured Z-pins reinforced woven CMC is feasible.

On the static and dynamic properties of flax and Cordenka epoxy composites

Fibre reinforced composites have excellent specific properties and are widely sought after by engineers seeking to reduce mass. However, end of life disposal is a significant problem and so research into more sustainable natural fibre composites is extremely topical. This paper examines the applicability of natural fibre composites for high performance structural applications. Woven flax and regenerated cellulose (Cordenka) textiles were pre-impregnated with commercially available epoxy resins and consolidated into test laminates in an autoclave to determine their static (compressive, tensile, flexural) and dynamic (energy absorption) properties. The range of compressive strengths was 77.5–299.6 MPa. Tensile strengths ranged from 63 to 92.6 MPa and interlaminar shear strength (ILSS) from 10.7 to 23.3 MPa. Specific energy absorption (SEA) varied between 21.2–34.2 kJ/kg. Biotex flax combined with MTM49 resin matched the SEA of T300 carbon fibre using the same resin system and layup. This work has demonstrated that natural fibre composites have significant scope for use in structural applications but additional work is required on fibre to matrix bonding in order to maximise their properties whilst remaining an environmentally credible option.

Influence of thermal treatment on thermo-mechanical stability and surface composition of carbon fiber

For investigating the influence of thermal treatment on the thermo-mechanical stability and the carbon fiber's surface composition, the T300 carbon fibers were thermally treated at temperatures ranging from 600°C to 1500°C. After treatment, the thermal stability and microstructure were analyzed by mass change and XRD measurement. The mechanical properties and the surface composition of carbon fibers were measured as a function of temperature by the single filament tensile test technique and ESCA analysis, respectively. The results indicated that T300 fiber had good thermal stability and high temperature mechanical properties. To some extent, the high temperature treatment could lead to a further graphitization of carbon fiber. The surface composition measured by ESCA revealed that the oxygen concentrations on the surface of fibers significantly decreased from 17.97% for as-received fiber to 1.97% for 1500°C treated fibers. But the relative content of graphite-like carbon increased from 42.97% for as-received fibers to 53.13% for 1500°C treated fibers. Such composition would result in a decreased surface activity of carbon fiber.

Effects of High Temperature on Tensile and Bending Strengths of T300 Carbon Fiber Three Dimensional Braided Composites

In this paper, the tensile and bending strengths of T-300 carbon fiber three dimensional braided/epoxy resin composites at 23 oC and 150 oC were researched. The results indicate that the effect of temperature on the tensile strength and bending strength of three dimensional braided composites is sentitive. However high temperature makes bending strength of 3D braided composites lost more than that of tensile strength of 3D braided composites. The average tensile strength of 3D braided composites at 150 oC is 65.06% of average tensile strength of 3D braided composites at 23 oC. The average bending strength of 3D braided composites at 150 oC is only 11.44% of average bending strength of 3D braided composites at 23 oC. This means that application temperature should be taken into account when 3D braided composites are used.

Measurement of Thermal Conductivity of CFRPs and Thermal Conductance of the Cold-to-Warm Joint at Low Temperatures

The cold-to-warm joint is often used in the cryogenic system to take advantages of both its thermal and mechanical performances. In this study, we report the experimental measurement of the thermal conductivity and thermal conductance of the cold-to-warm joint for the magnet using from cryogenic temperature to room temperature. The cold-to-warm joint is composed of the carbon fiber reinforced plastics (CFRP) cylinder and metal parts. Two kinds of CFRPs are made of the T300 and T700 carbon fibers and epoxy, respectively. The thermal conductivity of CFRP is measured by a 4 K G-M cryo-cooler based experimental facility and it is measured to be about 0.15-5.0 W/(m·K) in about 40 K to room temperature. And the thermal conductance of the cold-to-warm joint is also estimated based on the experimental data. Those results are essential information for designing the suspension structure in cryogenic applications.

Molecular dynamics simulations of interfacial adhesion between carbon fibers and various epoxies/hardeners and its calorimetric validation

Separate molecular dynamics simulations are carried out to study interfacial interactions between various monomers of epoxies and their hardeners with T300 and CCF300 carbon fibers. Atomistic models of T300 and CCF300 carbon fibers, both in sized and unsized states, are prepared on the basis of their X-ray Photoelectron Spectroscopy data. Calorimeteric measurement of heat of adsorption is used to validate the simulated values of interfacial interactions. Results demonstrate a ranking of epoxies and hardeners on the basis of their interfacial adhesion with T300 and CCF300 carbon fibers.