Woven Carbon Fabric Research Articles

Method of reducing the influence of speckles when processing diffraction patterns from moving woven materials

A program has been developed that makes it possible to reduce the noise level determined by the presence of speckles when woven materials are being monitored by laser diffraction. It is shown that, when one accumulates (adds up) the diffraction patterns obtained from metallic, synthetic, or carbon woven fabrics and considers the ratio of the intensity of the principal interference maxima in the cumulative diffraction pattern to the intensity of the speckles observed in them, one observes a growth of this ratio proportional to the number of additions. These results are explained on the assumption that the appearance of speckles in the diffraction pattern is caused by diffraction from randomly located inhomogeneities in the structure of the fabric that are always present inside the repeats of the weave in the illuminated section of the fabric.

Energy Absorption of Nano-Reinforced and Sandwich Composites in Ballistic and Low-Velocity Punch-Shear

This paper presents an investigation on energy absorption characteristics of nano-reinforced panels, laminated face sheets and sandwich composites in high velocity ballistic and low velocity punch-shear experiments. The vinyl ester panels were reinforced with 1.25 and 2.5 wt. percent nanoclay and exfoliated graphite platelets. Three different face sheets were manufactured with E-glass, Owens Corning HP ShieldStrand? glass and T-700 Carbon woven fabric in vinyl ester; and one with the E-glass and graphite platelets impregnated vinyl ester matrix. The sandwich composites were fabricated with balsa, PVC foam, 3D-fiber reinforced Tycor? and fire resistant fly-ash based Eco-Core? cores in between E-glass/vinyl ester face sheets. Ballistic tests were conducted according to NIJ level III using a universal receiver equipped with a barrel to launch 0.308 caliber M80 ball round projectile at about 890 m/s. Low velocity punch-shear tests were performed at around 3 m/s according to ASTM D3763 Standard using a drop-weight impact test system. The tortuosity of the fractured surface in nanocomposite specimens has been investigated using digital microscope. In ballistic tests, the 3-D fiber reinforced Tycor? core provided the most resistance when projectile strikes at the web-flange interface region. The 2.5 wt. pct. graphite platelet reinforced nanocomposite, HP ShieldStrand? glass vinyl ester face sheets, and E-glass/Eco-Core? sandwich composite showed the best energy absorption under low velocity punch-shear.

Hybrid composite laminates reinforced with glass/carbon woven fabrics for lightweight load bearing structures

Light-weight structure utilising novel design and advanced materials is one of the keys to improving the fuel efficiency and reducing the environmental burden of automotive vehicles. To ensure the low cost of applying fibre-reinforced materials in automotive vehicles, it is proposed to selectively incorporate carbon fibres to enhance glass fibre composites along main loading path. This paper investigates the influences of stacking sequence of on the strength of hybrid composites comprising materials with differing stiffness and strength. Hybrid composite laminates were manufactured using varying ratio of glass woven fabric and carbon woven fabric in an epoxy matrix. Static tests including tension, compression and three-point-bending were carried out to composite coupons containing various ratios of carbon fibres to glass fibres. The results show that hybrid composite laminates with 50% carbon fibre reinforcement provide the best flexural properties when the carbon layers are at the exterior, while the alternating carbon/glass lay-up provides the highest compressive strength. The tensile strength is insensitive to the stacking sequence. Analytical solutions are also developed and are shown to provide good correlation with the experimental data, which allow the optimisation of stacking sequence of hybrid composites to achieve the maximum strength.

Evaluation of tension-compression and tension-tension fatigue life of woven fabric glass/epoxy laminate composites used in railway vehicle

In this study, the fatigue characteristics and life of two types of woven fabric glass /epoxy laminate composites with WR580 glass fiber for carbody structures and GEP224 glass fiber for bogie frames were evaluated and compared with those of conventional metallic materials. Additionally, the laminate composite for carbody structures was reinforced with carbon plies to investigate the improvement of fatigue life. A fatigue test was conducted for tension-tension and tension-compression load with a stress ratio, R of 0.1 and -1, and up to endurance limit of 107 with frequency of 5Hz. In tension-compression fatigue test, the anti-buckling jig was designed to prevent buckling of specimen induced by compressive load. The Goodman diagrams were introduced to evaluate the fatigue life of laminate composites. The test results showed that the fatigue life of the GEP224 woven fabric glass/epoxy laminate composite with the stacking sequence of warp direction had a good performance in comparison with that of SM490A used to existing metal bogie frame. Also, the fatigue performance of WR580 woven fabric glass/epoxy laminate composite with the reinforcement of woven fabric carbon /epoxy ply had shown a significant improvement than that of a bare specimen without reinforcement.

Thermal and Mechanical Properties of Epoxy/Carbon Fiber Composites Reinforced with Multi-walled Carbon Nanotubes

Multi-scale hybrid composite laminates of epoxy/carbon fiber (CF) reinforced with multi-walled carbon nanotubes (MWCNTs) were fabricated in an autoclave. For laminate fabrication, 0.5 wt% of pristine MWCNTs or silane-functionalized MWNCTs (f-MWCNTs) were dispersed into a diglycidyl ether of bisphenol-A epoxy system and applied on the woven carbon fabric. The neat epoxy/CF composite and the MWCNTs-reinforced epoxy/CF hybrid composites were characterized by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), tensile testing, and field emission scanning electron microscopy (FE-SEM). A significant improvement in initial decomposition temperature and glass transition temperature of epoxy/CF composite was observed when reinforced with 0.5 wt% of f-MWCNTs. The coefficient of thermal expansion (CTE), measured by TMA, diminished by 22% compared to the epoxy/CF composite, indicating an improvement in dimensional stability of the hybrid composite. No significant improvement in tensile properties of either MWCNTs/epoxy/CF composites was observed compared to those of the neat epoxy/CF composite.

Preparation of ion exchanger layered electrodes for advanced membrane capacitive deionization (MCDI)

A noble electrode for capacitive deionization (CDI) was prepared by embedding ion exchanger onto the surface of a carbon electrode to practice membrane capacitive deionization (MCDI). Bromomethylated poly (2, 6-dimethyl-1, 4-phenylene oxide) (BPPO) was sprayed on carbon cloth followed by sulfonation and amination to form cation exchange and anion exchange layers, respectively. The ion exchange layers were examined by Scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FT-IR). The SEM image showed that the woven carbon cloth was well coated and connected with BPPO. The FT-IR spectrum revealed that sulfonic and amine functional groups were attached on the cationexchange and anionexchange electrodes, respectively. The advantages of the developed carbon electrodes have been successively demonstrated in a batch and a continuous mode CDI operations without ion exchange membranes for salt removal using 100 mg/L NaCl solution.

Polyetherimide composites with gamma irradiated carbon fabric: Studies on abrasive wear

Abstract Interfacial adhesion between matrix and fiber is an important aspect in controlling performance properties of the composites. Carbon fibers are known for chemical inertness and hence limited wettability with the matrix and need prior surface treatment to improve its adhesion with the matrix. In this work, γ (gamma) irradiation technique with varying doses (0–300 kGy) was employed to the twill weave carbon fabric (CF) to develop composites with polyetherimide (PEI) matrix based on impregnation method followed by compression molding. Composites were characterized for interlaminar shear strength (ILSS) and abrasive wear performance. Improvement in the friction and wear properties was correlated with the improvement in ILSS as a result of CF treatment. Higher the treatment dose, higher was the ILSS and better was the tribo-performance. SEM studies on fibers indicated increased roughness of the surface as a consequence of treatment and dose. Fourier Transform Infrared Spectroscopy in Attenuated Total Reflectance (FTIR-ATR) mode indicated inclusion of functional groups (mainly carbonyl). Both these factors were responsible for enhancing the fiber–matrix interface. Various techniques such as adhesion test, fiber tension test and Raman spectroscopic analysis of CF were also exploited to analyze the influence of γ irradiation on CF.

Effect of Moisture and Temperature on Mechanical Properties of Graphite Composite Bipolar Plate for Proton Exchange Membrane Fuel Cell (PEMFC)

The fuel cell is considered to be a promising alternative energy source for the near future. A bipolar plate, which is the major component of the fuel cell, is always exposed to the moisture during operation, because one of the important functions of the bipolar plate is to facilitate water management within the cell. In order to use graphite composite materials as bipolar plate material for PEMFC, the effect of the moisture environment on the mechanical properties of bipolar plate is studied. Two types of specimens, one made of particulate graphite 90%-epoxy 10% composite 'with' woven carbon fabric, and the other 'without' carbon fabric, were fabricated. Both types of specimens were kept in three different environmental conditions: (1) dry at room temperature, (2) immersed in 85° C water for 100 h, and (3) immersed in 85° C water for 300 h. A series of experiments were performed with the samples of the two types: water absorption rate, strength and modulus from the bending and tensile tests were measured. The results showed that a steep increase of water absorption rate occurred at the beginning of the test followed by a slow increase afterwards. Total water absorption rate was lower for the specimens with fabric since the inserted carbon fabric has lower porosity and lower water absorption than the specimens without fabric made of graphite/epoxy composite. Bending strength and modulus decreased for both types of specimens. However, addition of carbon fabrics to the graphite-particle/epoxy composite increased the tensile strength significantly.

Compressibility of carbon woven fabrics with carbon nanotubes/nanofibres grown on the fibres

Growth of carbon nanotubes (CNT) or carbon nano-fibres (CNF) on carbon fibrous substrates is a way to increase the fracture toughness of fibre reinforced composites (FRC), with encouraging results reported in the recent years. If these nano-engineered FRC (nFRC) are destined to leave laboratories and enter industrial-scale production, a question of adapting the existing composite manufacturing methods will arise. The paper studies compressibility of woven carbon fibre performs (two types of fabrics) with CNT/CNF grown on the fibres using the CVD method. The results include pressure vs thickness and pressure vs fibre volume fraction diagrams for one and four layers of the fabric. Morphology of the nFRC is studied with SEM. It is shown that the pressure needed to achieve the target fibre volume fraction of the preform increases drastically (for example, from 0.05 MPa to more than 0.5 MPa for a fibre volume fraction of 52%) when CNT/CNF are grown on it. No change in nesting of the fabric plies is noticed. The poor compressibility can lower the achievable fibre volume fraction in composite for economical vacuum assisted light-RTM techniques and increase the pressure requirements in autoclave processing.

Influence of Plasma Treatment on Carbon Fabric for Enhancing Abrasive Wear Properties of Polyetherimide Composites

Interfacial adhesion between matrix and fiber plays a crucial role in controlling performance properties of composites. Carbon fibers have major constraint of chemical inertness and hence limited adhesion with the matrix. Surface treatment of fibers is the best solution of the problem. In this work, cold remote nitrogen oxygen plasma (CRNOP) was used for surface treatment. Twill weave carbon fabric (CF) (55–58 vol%) was used with and without plasma treatment with varying content of oxygen (0–1%) in nitrogen plasma to develop composites with Polyetherimide (PEI) matrix. The composites were developed by compression molding and assessed for mechanical and tribological (abrasive wear mode) properties. Improvement in tensile strength, flexural strength, and interlaminar shear strength (ILSS) was observed in composites due to treatment. Similarly, improvement in wear resistance (WR) and reduction in friction coefficient (μ) were observed in treated fabric composites when slid against silicon carbide (SiC) abrasive paper under varying loads. A correlation between wear resistance and tensile strength was slightly better than that in Lancaster–Ratner plot indicating that ultimate tensile strength (S) and elongation to break (e) were contributing to control the WR of the composites. It was concluded that enhanced adhesion of fibers with matrix was responsible for improvement in performance properties of composites, as evident from SEM, Fourier Transform Infrared spectroscopy-Attenuated Total Reflectance (FTIR-ATR) technique.

Effect of Glass Fiber Hybridization on the Behavior Under Impact of Woven Carbon Fiber/Epoxy Laminates

The low-velocity impact behavior was studied in hybrid laminates manufactured by RTM with woven carbon and glass (S2) fabrics. Specimens with different thicknesses and glass fiber content (from 0 to 21 vol.%) were tested with impact energies in the range 30-245 J and the resulting deformation and fracture micromechanisms were studied using X-ray microtomography. The results of these analyses, together with those of the impact tests (maximum load and energy absorbed), were used to elucidate the role played by glass fiber hybridization on the fracture micromechanisms and on the overall laminate performance under low-velocity impact.

Characterization of SiC based composite materials by the infiltration of ultra-fine SiC particles

The fabrication route of SiC materials by the complex compound of ultra-fine SiC particles and oxide additive materials has been investigated. Especially, the effect of additive composition ratio on the characterization of SiC materials has been examined. The characterization of C/SiC composites reinforced with plain woven carbon fabrics was also investigated. The fiber preform for C/SiC composites was prepared by the infiltration of complex mixture into the carbon fabric structure. SiC based composite materials were fabricated by a pressure assisted liquid phase sintering process. SiC materials possessed a good density higher than about 3.0 Mg/m 3, accompanying the creation of secondary phase by the chemical reaction of additive materials. C/SiC composites also represented a dense morphology in the intra-fiber bundle region, even if this material had a sintered density lower than that of monolithic SiC materials. The flexural strength of SiC materials was greatly affected by the composition ratio of additive materials.

Characterisation of 3D woven composite internal architecture and effect of compaction

Yarn waviness and resin rich regions play a major role in 3D woven composite mechanical properties and failure. A detailed study of two angle interlock 3D woven carbon fabrics has been carried out to characterise these architectural features and how they change under increasing levels of compaction. Computerised tomography (CT) X-ray scanning was used to capture the internal architecture of the fabrics. The study focussed on the out-of-plane crimp of the yarns and the size and shape of resin rich regions in consolidated panels. Results showed areas of high local crimp at weft/weaver interlace points. This was exacerbated at low levels of compaction but was eventually lowered under higher compaction levels. The appearance of resin channels was found to be heavily dependent on weave style, with large resin pockets appearing in weaver yarn planes which decreased significantly in size under compaction with distinctive changes in profile.

Experimental device for the preforming step of the RTM process

This paper concerns the development of an experimental device which is able to form very complex double curved geometry. Objectives are to analyze the evolution of the woven preform during the forming process. This device contains one mechanical module containing the classical tools in forming process, (punch, blank holder, and open-die), and one optical module to measure the 3D-deformed shape and the distribution of local deformations, like shear angles of the woven reinforcement during all the process. Experimental results are obtained with an interlock carbon woven fabric, used in aeronautical applications. Wrinkling and buckling will be analyzed at the global scale of the piece. The evolution of the shear angle will be presented at local scale (on face, or edges of the geometry).

Work on Impact Properties of Foam Sandwich Composites with Different Structure

Foam core sandwich composites with various facings composed of glass, carbon woven, carbon/Kevlar hybrid, and Kevlar fabrics were fabricated by using RTM process, as well as the through-thickness stitched sandwich samples with glass fabrics; and impact performance was studied at three energy levels. This article proposes that the damage extent of foam core sandwich construction may be characterized by the average damage angle, penetration depth, and maximal cracking width. The results show that the foam core samples with Kevlar facing are optimal for the peak load at load—time plots and the lowest impact damage extent at the same energy level. Compared to the unstitched samples, the average damage angle of stitched samples increases by 48%, the maximal cracking width and penetration depth of stitched samples decrease by 67% and 4% at 25J impact energy level.

Effects of Carbon Yarn Size on the Mechanical Properties of Plain Woven C/SiC Composites

The effects of yarn size on the mechanical properties of silicon carbide composites reinforced with a plain woven carbon cloth with two sizes of yarns (1 and 3 k) were investigated. The experimental results show that the composite fabricated with 1 k yarns exhibits greater stiffness and strength than the composite fabricated with 3 k yarns. Microstructural observations revealed the existence of matrix microcracks in both the composites under the as‐processed condition due to the large difference of thermal expansion between the fibers and the matrix, which are more severe for the composite with 3 k yarns. The fractured surfaces of the composite with 1 k yarns showed extensive fiber pull‐out in contrast to the yarn pull‐out in the composite with 3 k yarns. The larger interyarn and intrayarn voids due to difficulties of matrix infiltration in the composite with 3 k yarns represent the primary contribution to the diminished mechanical properties. Unequal yarn sizes give rise to different yarn waviness, which may be another source of difference in the mechanical properties of composites.

Temperature Dependence of Resin Flow in a Resin Film Infusion (RFI) Process by Ultrasound Imaging

Ultrasonic imaging in the C-scan mode was used in conjunction with the amplitude of the reflected signal to measure the temperature dependence of resin flow rate in single layers of woven carbon fabric. The RFI samples were vacuum-bagged and scanned in a water tank at 50°C, 60°C, 70°C, and 80°C. The measured flow rates were plotted versus inverse viscosity to determine the permeability in the thin film, non-saturated system. The permeability values determined in this work were consistent with permeability values reported in the literature. Capillary flow was not observed at the temperatures and times required for pressurized flow to occur. The flow rate at 65°C was predicted from the measured flow rates, and then measured in a 10-layer laminate. The investigation demonstrates that ultrasonic imaging in the C-scan mode in conjunction with the amplitude of the reflected signal is an effective method for measuring resin flow through fabric.

In situ estimation of through-thickness resin flow using ultrasound

Ultrasonic imaging in the C-scan mode was used to measure the flow rate of an epoxy resin film penetrating through the thickness of a single layer of woven carbon fabric. Assemblies, comprised of a single layer of fabric and film, were vacuum-bagged and ultrasonically scanned in a water tank during impregnation at 70 °C. The permeability of the fabric was calculated using Darcy’s law. The results demonstrated that ultrasonic imaging in the C-scan mode is an effective method of measuring z-direction resin flow through a single layer of fabric. Comparison of ultrasonic and microscopy images yielded consistent results and demonstrated the effectiveness of ultrasonic imaging as an in situ process diagnostic for monitoring through-thickness impregnation and flow rates.

In vitro cytotoxicity assessment of carbon fabric coated with calcium phosphate

The success or failure of medical implants often depends on the cell-surface behavior after implantation of the device. This study investigated the use of woven carbon fabric, which had been sonoelectrochemically coated with calcium phosphate, to enhance bone cell attachment and proliferation in vitro. Human osteoblast-like cells, MG63, were used to study the interactions between cells and the material and assess the cytotoxicity of the substrates. The cytotoxicity of the materials was assessed using an MTS ((3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt)) assay to determine the viability of the osteoblast-like MG63 cells in direct contact with the carbon fabric or calcium phosphate coated carbon fabrics, and to assess the cytotoxicity of extracts from these materials. The morphology of the surface adherent cells was assessed by scanning electron microscopy (SEM). Results showed that neither carbon fabrics nor calcium phosphate coated materials were cytotoxic. Furthermore, cell attachment and proliferation were enhanced by coating carbon fabrics with calcium phosphate. SEM showed that the cells had a normal morphology and were well spread similar to those seen in the tissue culture plate control. These flexible calcium phosphate coated fabrics could, therefore, have uses in the reconstruction of bone in orthopaedic and dental surgery.

Electrical Characterization of GDL Materials for Polymer Fuel Cells (PEMFC)

A gas diffusion layer (GDL) in a Polymer Fuel Cell (PEMFC) has several important functionalities such as water management, uniform transport of reactant gases, gas permeability, mechanical support and compressibility, electrical and thermal conductivity both in-plane and through-plane. All these requirements are best met by carbon fiber-based materials such as carbon fiber paper, or simply a felt-like material or woven carbon fabrics. In this work, the attention is focused on a new series of GDL materials which were realized by an Italian industry, SAATIgroup. In particular, the attention was focused on two different surface treatments in order to make the GDLs samples hydrophobic. Three different kinds of samples were tested: a first sample with a coating of PTFE, a second sample with a plasma treatment and the third one without any surface treatment.