Carbon Fiber Mat Research Articles

Analytical and experimental evaluation of elastic properties of vacuum assisted resin infusion molded polymer composites with eight‐harness woven fiber mats

AbstractAn analytical and experimental evaluation of elastic properties of composite materials under tensile load is presented in this paper. The analysis focuses on composite materials molded by vacuum assisted resin infusion molding (VARIM). The molded composite structure consists of AS4‐8 harness carbon fiber mats and a high‐temperature polymer (5250‐4‐RTM). The analytical model presented is adapted and formulated using optical microscopy observations of cross sections of samples molded by VARIM. Effects of resin degree of cure, fiber undulation, and resin rich areas between fiber bundles are addressed in the model. An experimental case study is presented to evaluate the accuracy of the adapted analytical model. The evaluation shows a reasonable agreement between the experimental and analytical results. POLYM. COMPOS., 29:63–71, 2008. © 2007 Society of Plastics Engineers

Sensor Characteristics of Carbon Fiber Mat

Structural health monitoring (SHM) is becoming a popular topic. Carbon fiber reinforced concrete (CFRC) is an intrinsically smart material that can sense strain. The resistivity increases reversibly under tension and decreases under compression. A new skin-like sensor —cement-based smart layer had been put forward, which can serve as whole field strain sensor. The smart layer is satisfactorily consistent with concrete structure. The smart layer is a thin carbon fiber mat cementbased composite material layer with finite electrodes. It can cover the surface of concrete structure, and provide on-line reliable information about the deformation of whole concrete structure. The static characteristics of the new-type sensor had been researched. Its gage factor is 20-25 under tension and 25-30 under compression within the elastic deformation range. Furthermore the smart layer has satisfactory linearity and repeatability. In this paper, the sensor characteristics of the bare carbon fiber mat have been reached. The resistivity of carbon fiber mat has good agreement with strain under uniaxial tension. The gage factor can be up to 375, and the sensor limit can be up to 10000 microstrain. The strain and the fractional change in electrical resistance .R/R0 are totally reversible and reproducible under cyclic loading and amplitude-variable cyclic tensile loading.

Electrophoretic Deposition of Ceramic Powders-Influence of Suspension and Processing Parameters

The electrophoretic deposition (EPD) of AlN, Al2O3 and SiC, respectively, from ethanolic suspensions stabilised by suitable organic additives has been investigated. A main topic of this paper is the EPD in the direction of the gravitational force. Using an AlN suspension, the deposit weight depending on the experimental parameters was determined. The deposition was carried out under constant voltage or constant current conditions. Several factors influencing the effective electric field strength will be discussed. It could be shown that the conductivity of the suspension results mainly from the free ionic species. By EPD from the different suspensions, green bodies with monomodal pore size distributions were produced. The electrophoretic deposition of alumina from an ethanolic and from an aqueous suspension of the same composition led to similar results regarding the homogeneity of the particle packing in the deposits. The SiC suspension was also used for infiltrating woven carbon fibre mats by EPD in order to fabricate ceramic matrix composites.

Mats and Fabrics for Electromagnetic Interference Shielding

Fabrics (with continuous electrically conductive fibers) are more effective than mats (with discontinuous conductive fibers) for electromagnetic interference shielding. Conductive fibers in the form of metal-coated polymer fibers or metal-coated carbon fibers are more effective than those in the form of bare carbon fibers. The highest shielding effectiveness of 53 dB at 1.0 GHz was attained by a metal-coated polymer fabric. The shielding is due mainly to reflection. A higher shielding effectiveness correlates with a higher reflectivity and a lower electrical resistivity. Both shielding effectiveness and reflectivity decrease with increasing frequency from 300 kHz to 1.5 GHz. The shielding effectiveness increases with thickness, as shown for bare carbon fiber mats. A nickel-coated carbon fiber mat of areal weight 9 g/m2 is similar to a bare carbon fiber mat of areal weight 17 g/m2 in shielding effectiveness.

Deformation adjustment of concrete beams laminated with carbon fiber mats

A carbon fiber mat is a sheet composed of intercrossing short carbon fibers, which has more stable and lower electrical resistivity compared with dispersed short carbon fiber mixed in cement. Thereby carbon fiber mats can be used in cement and then make cement structures exhibit obvious electro-thermal effect. In this paper, Electro-thermal properties of carbon fiber mats and an elementary strengthening experiments against deformation of carbon fiber mat cement laminated beams were researched. Firstly, electro-thermal properties of carbon fiber mats were studied. Secondly, carbon fiber mat laminated beams are designed and experiments were conducted to get temperature and deformation responses driven by the electro–thermal effects of the carbon fiber mat cement laminated beams. Finally, some experiments of deformation adjustment were done according to the above experimental results. The results show that deformation of concrete beams upon loads can be reduced even removed, and the beams can be strengthened against deformation.

Short-term static and cyclic behavior of two automotive carbon-fiber composites

Abstract The basic static (tensile, compressive, and in-plane shear) and fatigue properties, including temperature and fluid environment effects, for two carbon-fiber polymeric composites, produced by a rapid-molding process suitable for high volume automotive applications, are described. The two composites had the same urea/urethane matrix and were reinforced with stitch-bonded carbon-fiber mats, in a crossply layup in one case, and in a quasi-isotropic layup in the other. All properties were determined over a temperature range from −40 to 120 °C, and the degradation of the properties due to distilled water and windshield washer fluid was established. In all cases, two fiber orientations of the crossply, 0/90° and ±45°, relative to the specimen axes were addressed. As expected, matrix-dominated properties were degraded more by rising temperatures than were fiber-dominated properties. Fluid had only a modest effect in both cases. Basic fatigue behavioral characteristics were established through tensile fatigue tests over the temperature range of interest. An assessment of fatigue test results for the two composites revealed differences in a progressive loss in stiffness and an increase in permanent strain, both of which are indicative of increasing damage. In all cases, fatigue reduction factors were established to account for the effects of temperature and fluids.

Physical and numerical modeling of mold filling in resin transfer molding

AbstractFinite element modeling and experimental investigation of mold filling in resin transfer molding (RTM) have been performed. Flow experiments in the molds were performed to investigate resin flow behavior into molds of rectangular and irregular shapes. Silicone fluids with viscosity of 50 and 100 centistoke as well as EPON 826 epoxy resin were used in the mold filling experiments. The reinforcements consisted of several layers of woven fiberglass and carbon fiber mats. The effects of injection pressure, fluid viscosity, type of reinforcement, and mold geometry on mold filling times were investigated. Fiber mat permeability was determined experimentally for the five‐harness and eight‐harness woven mats. Resin flow through fiber mats was modeled as flow through porous media. Pressure distributions inside both types of molds were also determined numerically. In the case of resin flow into rectangular molds, numerical results agreed well with experimental measurements. Comparison between the experimental and numerical results of the resin front position indicated the importance of edge effects in resin flow behavior in small cavities with larger boundary areas. Reducing the resistance to resin flow at the edge region in the numerical model allowed for good agreement between the numerical simulation and the physical observations of the resin front position and mold filling time.

Mold‐filling simulations for the injection molding of continuous fiber‐reinforced polymer

AbstractInjection molding can be used to fabricate fiber‐reinforced polymer composites by impregnating a continuous fabric mat preplaced in a mold cavity with a polymer resin. The mold‐filling time is dependent on the flow and heat transfer behavior in the mold. A model is proposed that considers the non‐Newtonian How through the porous fabric mat and the heat transfer between mold, fabric mat, and flowing fluid. The model was simulated for the mold filling of a carbon fiber mat with a pseudoplastic polymer solution. The results from the simulation provide Information for optimizing mold‐filling parameters through proper selection of inlet fluid pressure, heat source temperature, and type of polymer‐solvent system.