Carbon Fiber Preforms Research Articles

The influence of processing techniques on the matrix distribution and filtration of clay in a fibre reinforced nanocomposite

A nano-modified matrix based on an epoxy resin and montmorillonite (MMT) layered silicates, was successfully infiltrated through 10 ply of carbon fibre preform. A combined fabrication process of a vacuum assisted resin infusion method (VARIM) followed by a rapid heating rate and mechanical vibration during cure, facilitated the infiltration of the nano-modified matrix through the preform. This was achieved by dispersing the MMT clay in the resin and ensuring that the viscosity of the nano-modified matrix remained low during fabrication. SEM-EDX (energy dispersive X-ray spectroscopy) spectra showed that chemical constituents within MMT clay including silicon, aluminium and magnesium elements had permeated through the fibre preform and were detected throughout the laminate. A homogeneous resin/particle distribution was achieved with the size of clay particles ranging from 100 nm to 1 μm.

Fabrication of PyC/SiC Compound Coating on Carbon Fiber Preform and Its Effect on the Properties of Cf/Al Composite

Abstract PyC/SiC compound coating was deposited on carbon fiber preform by chemical vapor deposition (CVD) process for improving the wettability and reducing the chemical reaction between molten aluminum alloy and carbon fibers. Cf/Al composites were fabricated through the extrusion directly following vacuum pressure infiltration process. Effects of coating deposition parameters on the quality of carbon fiber coating were studied, and the influences of the coating on the infiltration quality and the mechanical properties of composites were also investigated by means of the microstructural analysis and mechanical property tests. The results show that the deposition rate of the coating is mainly controlled by the deposition temperature, and the uniform thickness of PyC/SiC compound coating can be obtained by controlling the deposition temperature or deposition time. The coating on carbon fiber preform can improve the infiltration quality and mechanical properties greatly based on the suitable interface bonding strength and good wettability. The optimized PyC/SiC compound coating thicknesses are 0.068 µm (PyC coating) and 0.257 µm (SiC coating) for better improving the composite properties.

An experimental study of the influence from fibre architecture on the permeability of 3D-woven textiles

In this work experimental measurements of the permeability of fully interlaced 3D-woven carbon fibre preforms are performed using the unsaturated parallel flow method. The effect on the permeability from three different parameters is studied by altering the architecture of woven preforms and varying mould sizes in a duct flow set-up. Influences from the geometrically different surface layers of the woven preforms, from fibre volume fraction and from warp yarn crimp are studied. The measurements show negligible influence on the permeability from crimp and the fraction of weave surface layers while the fibre volume fraction has a prominent influence. However, the effect is not consistent in terms of fibre volume fraction variation alone but depends on how it is varied.

Electrical resistivity prediction of dry carbon fiber media as a function of thickness and fiber volume fraction combining empirical and analytical formulas

The transverse electrical resistivity of the dry unidirectional carbon fiber preforms was studied experimentally taking into consideration various parameters. The dependency of the electrical resistivity transverse to the fibers was thoroughly experimentally studied as a function of the preform thickness and the fiber volume fraction. Empirical mathematical relations were extracted and combined with a non-linear compaction semi-analytical formula. The extracted formula consolidates the compressibility of the preform material, the preform thickness and the fiber volume fraction or the applied pressure in order to calculate the electrical resistivity of the unidirectional preform material transverse to the fibers. Two electrical resistance measurements, at two different thicknesses and two electrical resistance measurements, at two different pressure levels, are necessary to obtained, in order to predict the full range of the electrical resistivity values of the preform material transverse to the fibers as a function of thickness and fiber volume fraction. Very good agreement between the proposed formulas and the experiments has been obtained.

Damage tolerance of composite T-sections made of cost-effective carbon fibre preforms

Purpose – T-sections of carbon fibre-reinforced composites are prone to delamination because they lack reinforcement through their thicknesses. The purpose of this paper is to present the structural response of cost-effective laminated T-sections when subjected to various types of loads and impacts. Design/methodology/approach – The core of the automated manufactured beams is analysed. Pull-off, flange tension, and flange bending were tested for specimens extracted from an I-beam. The failure processes for all of the specimens were investigated in detail, leading to the statistical evaluation of the failure modes. Findings – A correlation is apparent between the impact damage energy and certain fracture patterns. These results can be used to assess damage tolerance when designing stiffeners, beams, and various complex structures. The increase in strength by 25 per cent was measured for the advanced stitching located in the web section for the flange tension test. Originality/value – The resistance displayed by the T-sections toward impact damage was studied experimentally, as the literature describing this topic is limited. The prevalence of one fracture mode for higher impact energies shows a possible advantage of the cost-effective preforms for the damage tolerant philosophy.

Effect of oxidation on the damping behavior of 2D C/SiC composites

A carbon fiber preform was chemical vapor infiltrated with a pyrocarbon (PyC) interphase and a SiC matrix, and then coated with a SiC outer layer by chemical vapor deposition to prepare 2D C/SiC composites with a density of 2.1 g/cm3. The composites were oxidized at 700, 1000, 1300 °C for 2, 5 and 10 h, respectively. The damping behavior of the oxidized composites was measured by a dynamical mechanical analyzer and the microstructural damage produced by the oxidation was investigated by scanning electron microscopy. Results show that the damping of the composites oxidized at 700 °C and 1000 °C increases initially and then decreases with increasing oxidation time while that of the composites oxidized at 1300 °C is independent of the oxidation time.The damping capacity of the C/SiC composites is determined by the carbon fibers, PyC interphase, SiC matrix and their interaction. The oxidation of the composites increases the damping by weakening the interfacial bonding due to the oxidation of PyC during the initial stage of oxidation, and decreases the damping by the oxidation loss of carbon fibers and excessive damage of the PyC interphase during the latter stages of oxidation. SiO2 formed at 1300 °C by the oxidation of SiC fills the voids produced by carbon oxidation, which increases the damping and compensates for the decrease of damping produced by carbon loss and excess damage of the PyC interphase. [New Carbon Materials 2014, 29(6): 522–528]

Effect of fiber orientation on mechanical properties of 2D-Cf/Al composites by liquid–solid extrusion following Vacuum infiltration technique

Through the method of fiber lamination, carbon fiber preforms with different orientation angles of 30°, 45°, 60° and 90° were prepared, and 2D-Cf/Al composites were fabricated by liquid–solid extrusion following the vacuum infiltration technique (LSEVI). Through mechanical properties test of the above composites, it showed that ultimate tensile strength (UTS) of the obtained Cf/Al composite was improved more than that of the matrix alloy. It was found that the volume fraction of four kinds of preform was about 45%. Fibers were arranged according to a certain direction, and this was very helpful in improving the performances of composites. In the preparation process, squeeze pressure was far greater than theoretical calculated value, and this was because many infiltration factors had been simplified and ignored in the theoretical calculation model. Infiltration of composites was sufficient and uniform and obvious defects could not be found. Tensile fracture was uneven, indicating that fibers played the reinforced role effectively, which also improved the properties of the composites greatly. Meanwhile, the increased rates of composites׳ UTS with different angles had large differences. When the angles were 45° and 90°, the increased rates were 112.5% and 63.9%, respectively. Through theoretical analysis and experimental comparison, it was concluded that the total fiber bearing capacities were the key dominant factor.

Investigations on pressure and thickness profiles in carbon fiber-reinforced polymers during vacuum assisted resin transfer molding

Systematic experiments have been carried out by monitoring the in-situ pressure and thickness profiles for three different configurations, viz., flat plate, flat plate with a central circular hole, and an L-section using vacuum assisted resin transfer molding (VARTM) process. The effect of anisotropy on resin flow has been quantified by considering uni-directional carbon fiber preforms with 0° and 90° orientation to the flow direction for each configuration. A quasi-isotropic [45°/0°/−45°/90°]S layup has also been included for flat plate case. Additionally, the study has been extended to understand the effect of using high permeability medium for each configuration. Fluid pressure profiles and thickness variation profiles have been obtained using an array of pressure sensors and linear variable differential transformers for each configuration. Experimental data reveal that anisotropy (due to changing fiber orientations), configuration, and gravity significantly change fluid pressure and displacement fields obtained during VARTM.

Residual thermal stresses in carbon/carbon–Zr–Ti–C composites and their effects on the fracture behavior of composites with different preforms

Carbon/carbon(C/C)–Zr–Ti–C composites were fabricated using chemical vapor infiltration and liquid metal infiltration processes. The residual thermal stress (RTS) distribution in the C/C–Zr–Ti–C composites was analyzed by Raman spectroscopy and finite element (FE) calculation. The mechanical behaviors of C/C–Zr–Ti–C composites with three types of carbon fiber preforms were tested. The results showed that there was very high compressive RTS in the fibers and high tensile RTS in the pyrocarbon (PyC) in the marginal region near the carbide. However, in the central region away from the carbide, relatively low compressive stress and tensile RTS were found in the fibers and PyC, respectively. The FE analysis showed that the introduction of carbide into the C/C composites caused a significant increase of the RTS in the PyC near the carbide, indicating that the carbide could change the RTS distribution in C/C composites. Moreover, the distribution of the RTS and its release combined with the carbide distribution and fiber architecture led to variations in the mechanical performance of composites with different preforms.

Carbon Fiber Reinforced SiC Matrix Composites Fabricated by Preceramic Impregnation and Pyrolysis Process Combining SiC Nano Powder Infiltration

SiC nanopowder, polycarbosilane and divinylbenzene mixed slurries were prepared for viscosity measurement, which were used as matrix source of ceramic matrix composites. Results showed that apparent viscosity of the slurries increased with the increase of the content of SiC particles. The slurries with 50 nm SiC particles showed a low viscosity as compared with those slurries with 20 nm or 120 nm SiC particles at the same content of SiC. In particular, when the viscosity of slurry was higher than 30 mPa•s, the slurry could not be used in the test. Three-dimensional carbon fiber (3D-Cf) preforms were infiltrated with the aforementioned slurries. Addition of the nanoSiC powder as the inert filler in the slurries led to reduce the porosity and the infiltration–curing–pyrolysis cycles to manufacture 3D-Cf/SiC composites by the subsequent polymer impregnation and pyrolysis (PIP) process. Characterizations of the composites showed that the maximum flexural strength of specimen in the composites was 326 MPa and its fracture toughness was 10.5 MPa•m1/2.

Novel form-flexible handling and joining tool for automated preforming

AbstractThe production rates of carbon fiber reinforced plastic (CFRP) parts are rising constantly which in turn drives research to bring a higher level of automation to the manufacturing processes of CFRP. Resin transfer molding (RTM), which is seen as a production method for high volumes, has been accelerated to a high degree. However, complex net-shape preforms are necessary for this process, which are widely manually manufactured. To face these challenges a new concept for the manufacturing of carbon fiber preforms with a form-flexible gripping, draping and joining end-effector is presented and discussed. Furthermore, this paper investigates the application of this concept, describes the initial build-up of a demonstrator, focusing on material selection and heating technology, and discusses test results with the prototype. This prototype already validates the feasibility of the proposed concept on the basis of a generic preform geometry. After a summary, this paper discusses future in-depth research concerning the concept and its application in more complex geometries.

Effects of yarn size and Z-yarn density on the interlaminar shear properties of two Z-reinforced 3D C/SiC composites

This work investigated the effects of yarn size and Z-yarn density on the interlaminar shear strength (ILSS) of two 3D C/SiC composites fabricated by chemical vapor infiltration. They were the 3D needled (3DN) composite and the 3D stitched (3DS) plain woven composite, respectively. For 3DN C/SiC, short-cut fiber lamina was confirmed as the initial facture source. Large yarn size resulted into the occurrence of 0° non-woven fiber lamina fracture source and increased the crack extending paths. The ILSS of textile preforms indicates ILSS of their composites. The existing knowledge had displayed that increasing Z-yarn density increased the ILSS of 3DN carbon fiber preform. Thus the ILSS of 3DN C/SiC increased with increasing yarn size and Z-yarn density. For 3DS C/SiC, the interlaminar region was considered as the initial fracture source and caused the matrix crack sources in the weft and warp yarn. Large yarn size alleviated SiC densification effect of preform while high Z-yarn density enhanced Z-pinning effect and SiC densification effect of interlaminar region. Thus the ILSS of 3DS C/SiC decreased with increasing yarn size and decreasing Z-yarn density.

Assessment of the interfacial properties from fatigue hysteresis loss energy in ceramic-matrix composites with different fiber preforms at room and elevated temperatures

The fiber/matrix interface shear stress is a key parameter in the fatigue behavior of fiber-reinforced ceramic-matrix composites (CMCs). In this paper, the interface shear stress of three CMCs with different carbon fiber preforms, i.e., unidirectional C/SiC, cross-ply C/SiC and 2.5D woven C/SiC, has been estimated from fatigue hysteresis loss energy at room and elevated temperatures. Under fatigue loading, the fatigue hysteresis loss energy and fatigue hysteresis modulus versus the applied cycles have been analyzed. The theoretical relationships between the fatigue hysteresis loops, the fatigue hysteresis loss energy, the interface slip and the interface shear stress have been established. When the interface shear stress degrades, the fatigue hysteresis loss energy first increases to the maximum value, then decreases to zero; the fatigue hysteresis loops correspond to different interface slip cases. By comparing the experimental fatigue hysteresis loss energy with theoretical computational values, the evolution of the interface shear stress versus the applied cycles of C/SiC composites has been analyzed. The effects of fiber preforms and test conditions on the interface shear stress degradation have been investigated. The fatigue hysteresis loops of unidirectional, cross-ply and 2.5D woven C/SiC composites have been predicted for different applied cycles at room and elevated temperatures.

A new approach to fabricate SiC nanowire-embedded dense SiC matrix/carbon fiber composite

A novel and simple sol-gel route has been used for the fabrication of composite structure composed of carbon fibers and silicon carbide nanowires embedded in dense silicon carbide matrix. The carbonaceous silica sol was impregnated in the carbon fiber preform at atmo- spheric pressure. The sol impregnated carbon preform was cured and heat treated to convert into silicon carbide. The analysis by X-ray diffraction, scanning electron micros- copy, X-ray tomography, and transmission electron microscopy indicates that the impregnated carbonaceous silica gel converts to b-silicon carbide with dense and wire morphology. Different morphological silicon carbide was uniformly distributed inside carbon fiber preform and there was no degradation in thermophysical properties of carbon composite during processing. These results reveal high efficient reinforcement of different morphological silicon carbide in carbon composite, demonstrate a new mecha- nism of carbon composite reinforcement and suggest a new direction to carbon composite reinforcement.

Synthesis and Characterization of Hyperbranched Polyazomethine Ablators for Space Exploration Applications

A novel series of ablative composites containing a hyperbranched polyazomethine synthesized inside a carbon fiber preform (HyPAZA) were prepared, which have similar density to phenolic impregnated carbon ablators (). A novel method of synthesizing strong hyperbranched polyazomethine thermosets has been developed, enabling polyazomethines to be studied in ablators for the first time. Several formulations of HyPAZA perform better than the phenolic impregnated carbon ablator in terms of polymer char yield, composite mechanical strength, laser ablation tests at heat fluxes of 550 and , and small-scale arcjet testing at a heat flux of . Char yields of hyperbranched polyazomethines were as high as 79% at 1000°C by thermogravimetric analysis. This is one of the highest char yields ever reported for a fully organic polymer. Some HyPAZA composites are over 10 times stronger than the carbon fiber preform, as determined by compression tests. Specimens were also tested in an arcjet facility at . Several formulations exhibited better performance than the phenolic impregnated carbon ablator in terms of ablation rate by a factor of 1.2 to 1.7. In addition, HyPAZA composites impregnated with aerogel show a lower rate of increase of back wall temperature, and therefore a lower thermal conductivity.

Preparation and Microstructure Characterizations of Novel C/C-Zr(Hf)B<sub>2</sub>-Zr(Hf)C-SiC Composites

A series of novel C/C-Zr (Hf)B2-Zr (Hf)C-SiC composites were prepared by chemical vapor infiltration (CVI) of pyrolytic carbon and polymeric impregnation and pyrolysis (PIP) with hybrid polymeric precursors of SiC (polycarbosilane), Zr (Hf)C and Zr (Hf)B2 in carbon fiber preforms. The formed ultra-high temperature ceramics (UHTCs) matrix of SiC-ZrC-ZrB2 and SiC-HfC-HfB2 were designed to improve the oxidation resistance of carbon/carbon composite at very high temperatures above 2000°C. The pyrolysis process of Zr (Hf)C and Zr (Hf)B2 polymeric precursors was investigated, and the results showed that the hybrid precursors could be successfully transformed into Zr (Hf)C and Zr (Hf)B2 ceramic particles with the sizes of nanometer with temperatures above 1500°C. Furthermore, the multiscale structure of C/C-Zr (Hf)B2-Zr (Hf)C-SiC composites were also characterized , showing that the carbon fibers were covered by pyrolytic carbon, and the continuous ceramic matrix was well dispersed, formed by Zr (Hf)C and Zr (Hf)B2 nanoparticles distributing homogeneously in the continuous SiC matrix. This homogeneous dispersion of composite ceramics of Zr (Hf)C and Zr (Hf)B2 with SiC plays excellent protection of C/C composites from oxidation at high temperature via formation of stable oxides coatings.

3D Cf/ZrC–SiC composites fabricated with ZrC nanoparticles and ZrSi2 alloy

3D Cf/ZrC–SiC composites were fabricated via a combination process of polymer infiltration and pyrolysis and reactive melt infiltration with ZrC nanoparticles and ZrSi2 alloy. ZrC nanoparticles was first introduced into 3D needle-punched carbon fiber preforms by impregnating the mixture of ZrC nanoparticles and phenol resin, followed by pyrolysis at 900°C. As-prepared composites were densified by PIP with phenol resin for five cycles, and then were heat treated at a higher temperature. Molten ZrSi2 alloy was then infiltrated into the porous 3D Cf/ZrC–C to obtain 3D Cf/ZrC–SiC composites. Microstructure evolution associated with phase variation was investigated. Mechanical properties and ablation properties of 3D Cf/ZrC–SiC composites were reported. Results show that ZrC nanoparticles have important roles in the fabrication procedure of 3D Cf/ZrC–SiC and that the mechanical properties of 3D Cf/ZrC–SiC composites can be further improved. The mass loss rate and linear recession rate of 3D Cf/ZrC–SiC composites without F/M interphase are 3.4×10−3g/s and 2.1×10−3mm/s, respectively.

Porous-Material Analysis Toolbox Based on OpenFOAM and Applications

The Porous-material Analysis Toolbox based on OpenFOAM is a fully portable OpenFOAM library. It is implemented to test innovative multiscale physics-based models for reacting porous materials that undergo recession. Current developments are focused on ablative materials. The ablative material response module implemented in the Porous-material Analysis Toolbox relies on an original high-fidelity ablation model. The governing equations are volume-averaged forms of the conservation equations for gas mass, gas species, solid mass, gas momentum, and total energy. It may also simply be used as a state-of-the-art ablation model when the right model options are chosen. As applications, three physical analyses are presented: 1) volume-averaged study of the oxidation of a carbon-fiber preform under dry air, 2) three-dimensional analysis of the pyrolysis gas flow in a porous ablative material sample facing an arcjet, and 3) comparison of a state-of-the-art and a high-fidelity model for the thermal and chemical response of a carbon/phenolic ablative material.

Effect of nickel introduced by electroplating on pyrocarbon deposition of carbon-fiber preforms

In order to improve the deposition rate and microstructure of pyrocarbon, nickel was introduced by electroplating on carbon fibers and used as a catalyst during the deposition of pyrocarbon at 1000°C using methane as a precursor gas. The distribution of nickel catalyst and the microstructure of pyrocarbon were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Raman micro-spectrometry. Results show that nano-sized nickel particles could be well distributed on carbon fibers and the pyrocarbon deposited catalytically had a smaller d002 value and a higher graphitization degree compared with that without catalyst. In addition, the deposition rate of pyrocarbon in each hour was measured. The deposition rate of pyrocarbon in the first hour was more than 10 times when carbon cloth substrates were doped with nickel catalysts as compared to the pure carbon cloths. The pyrocarbon gained by rapid deposition may include two parts, which are generation directly on the nickel catalyst and formation with the carbon nanofibers as crystal nucleus.

Plastic Micromechanical Response of 2D Cross Ply Magnesium Matrix Composites

2D cross ply magnesium matrix composites were fabricated by melt magnesium infiltration in carbon fiber preform. Carbon fiber uni-directional fabric was used to prepare the carbon fiber preform by alternatively placing fabric in orthogonal way layer by layer. Preform was strengthened by stitching in the perpendicular direction to the fabric layers. The micromechanical model was generated based on the real microstructue of 2D cross ply magnesium matrix composites. The plastic response of 2D cross ply magnesium matrix composites was predicted based on the constructed micromechanical model by applying tensile load in different direction with respect to the fabric direction. Effects of layer mode and packing mode on the plastic response were investigated by numerical simulation. The results showed that composites were strengthened maximally along the fabric direction. Layering mode of fabric played important role on the plastic response of composite. The best layer mode for maximum properties improvement was that perpendicular layer and parallel layer should be used alternatively. The simulated results were verified through corresponding experiments.