Thermal Diffusivity Of Composites Research Articles

Experimental investigation on fabrication, characterization and properties of spark plasma sintered alumina-based tungsten carbide composites reinforced by carbon nanotubes

In this study, the alumina-based tungsten carbide (WC-Al2O3) composites reinforced by different weight percentages of carbon nanotubes were successfully prepared by the advanced spark plasma sintering technique. This study has the novelty that such composites with the given compositions were never sintered before using spark plasma sintering. The WC-Al2O3-CNTs composites were fabricated to design advanced tool materials with an optimum set of mechanical and thermal properties for high-temperature cutting applications. The experimental results revealed considerable growth in micro-hardness and fracture toughness in WC-Al2O3-CNTs composites as compared to WC-Al2O3 composites. The ideal set of mechanical properties was acquired by WC-Al2O3-CNTs-0.5 composite which also exhibited a minimum value of grain size. At higher concentrations of carbon nanotubes, the mechanical properties of composites tend to degrade due to the agglomeration of carbon nanotubes. The study presented better results in sintered composites than the composites fabricated through other sintering techniques. The improved strengthening and toughening results of WC-Al2O3-CNTs composites along with the fine microstructures were mainly acquired by inhibiting grain growth during sintering, improved dispersion of the constituents in the composites (electron probe microscopy analysis/wavelength dispersive spectroscopy mapping) and consolidation at shorter sintering periods in spark plasma sintering. A thermal study was also conducted to discuss the thermal stability of sintered composites at ambient as well as at higher temperatures to estimate the behavior of thermal conductivity and thermal diffusivity of composites at different temperatures.

Thermo-physical and fire properties of sustainable bio composites: Experimental and computational analysis

ABSTRACT Bio-composites were prepared by incorporating broom grass, fishtail palm, sansevieria fibers as reinforcement in unsaturated polyester resin using hand lay-up method. The thermo physical and fire properties of bio-composites has been examined by varying the fiber content (0 to 39 wt. %) and temperature (30–120°C). The thermal insulation and heat storage capability of samples was assessed using guarded heat flow meter and differential scanning calorimeter. The experimental results reveal that, as the weight fraction of fiber increased, the insulation capability of composites increased, whereas it decreased with the temperature. The response of specific heat and thermal diffusivity of composites with temperature was analyzed. Temperature distribution and heat transfer through the composite materials was computed using ANSYS fluent solver. The rate of heat transfer through the fishtail palm fiber composite is 14.02% lesser than glass fiber composite. Cone calorimeter was used to measure fire behavior of the samples and the results reveal that the broom grass fiber composite material possesses better fire resistance characteristics against fire hazard. Morphological study of composites was performed with the help of Scanning Electron Microscopy (SEM) for the visualization of homogeneity of surfaces. Developed bio-composites are the potential materials to replace petrochemical-based products.

Synthesis and properties of TiB2/Ti3SiC2 composites

The present study aims to investigate the effect of reinforcing TiB2 particles on the properties of in situ synthesized Ti3SiC2. For this purpose, TiB2/Ti3SiC2 composites with 5, 10, and 15 wt%TiB2 addition were synthesized through spark plasma sintering. TiB2/Ti3SiC2 composites were fabricated by this technique for the first time and the effect of TiB2 addition was evaluated comprehensively in terms of sintering behavior and density, phase development, microstructure, mechanical, thermal, and wear properties. Fully densified TiB2/Ti3SiC2 composites without the formation of any impurity phases were obtained at 1300 °C, for 15 min, under a pressure of 50 MPa. The mechanical properties and thermal diffusivity of composites were increased with the increasing TiB2 content. The most significant effect of TiB2 addition was obtained in wear properties compared to Ti3SiC2 matrix.

Effect of Thiodiphenol-Based Epoxy Resin on the Thermal Properties of an Aluminum Oxide Composite

The effects of thiodiphenol based epoxy resin on the thermal property of the composites containing aluminum oxide were investigated. The thermal conductivities and thermal diffusivities of the composites were dependent on the polymer resin. At the same content of Al₂O₃, the thermal conductivity and thermal diffusivity of composites made by synthesized polymer resin exhibited higher than that of composite made by bisphenol-A resin. The obtained maximum thermal conductivity of the composite was 0.25 W/mK, which was 0.4 times as large as that of the conventional bisphenol-A epoxy resin which has an amorphous structure. It is supposed that the reason for the high heat conductivity obtained in thiodiphenol based epoxy resin is certain high packing structure.

Low-Energy Ablation and Low Thermal Diffusivity of a CFRC Composite Modified by SiC

The use of materials for aerospace devices, such as rocket nozzles and thermal shields, depends primarily on their thermal and structural characteristics. Ceramic materials and carbon composites have been studied for this purpose. This work measures and investigates the ablation and thermal diffusivity of hybrid matrix composites of carbon–silicon carbide matrix reinforced by carbon fiber (C/C-SiC). Silicon powder was added to a phenolic thermoset matrix with proportions of 5, 10, and 20 %. In addition, the liquid polymer infiltration (LPI) process using a silicone polymer was used to produce the same composites. A thermal plasma torch was used to obtain the ablation and effective thermal diffusivity characteristics of the materials. The morphologies, microstructures, and chemical compositions of the samples were investigated by scanning electron microscopy and energy-dispersive spectrometry (SEM/EDS) and X-ray diffraction (XRD). The thermal diffusivities of the composites were found to be in the range of 0.2–1.5 × 10−6 m2·s−1 from 700 °C to 1000 °C, respectively. The void volume fraction of the composites was approximately 20 % and decreased the thermal diffusivity.

Thermo physical properties of Jute, Pineapple leaf and Glass fiber reinforced polyester hybrid composites

The objective of this study is to examine the variation in thermal conductivity, specific heat capacity and thermal diffusivity of composites with respect to fiber content and temperature. The fiber content in the composites was varied from 0.18 to 0.42 by volume. The results revealed that the thermal conductivity of composite decreased with increase in fiber content and the quite opposite trend was observed with respect to temperature. The specific heat capacity of the composite as measured by differential scanning calorimeter showed similar trend as that of the thermal conductivity. It was observed that the thermal diffusivity of composite was influenced by the fiber content, and the variation of thermal diffusivity with temperature was not so significant.

Study on thermo physical properties of hemp, jute and glass fiber reinforced polyester composites

The objective of this study is to examine the variation in thermal conductivity, specific heat capacity and thermal diffusivity of composites with respect to fiber content and temperature. The fiber content in the composites was varied from 18 to 36 by volume percentage. The results revealed that the thermal conductivity of composite decreased with increase in fiber content and the quite opposite trend was observed with respect to temperature. The specific heat capacity of the composite as measured by differential scanning calorimeter showed similar trend as that of the thermal conductivity. It was observed that the thermal diffusivity of composite was influenced by the fiber content, and the variation of thermal diffusivity decreased with increase in temperature at maximum volume of fiber.

Thermal diffusivity of ZTA composites with different YSZ quantity

In the present study, ZTA composites containing 0–10 vol% of 5mol% YSZ (in the range 0–10 vol%) were prepared by sol-gel technique followed by powder mixing and sintering up to 1650 °C for 1 h. Microstructure of the composites was observed using scanning electron microscopy and phase compositions was detected by means of X-ray diffraction. Density increased and grain size decreased with the increase of zirconia content. Thermal diffusivity of the composites; determined at various temperatures up to 1400 °C using laser flash technique; decreased with the increase of ZrO2 content and temperature.

Fabrication of novel (5, 10 and 15 mol.-%) CeO2+YSZ ceramic composites by spark plasma sintering

In this research, fabrication of 8 mol.-% yttria stabilised zirconia (YSZ) composites doped with 5, 10 and 15 mol.-% ceria (CeO2) via spark plasma sintering has been studied. Phase evolution during sintering and microstructural characterisation has been carried out with the help of X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Thermal diffusivity of composites has been studied using laser flash method. The results suggest that the cubic structure of YSZ can be retained even at 15 mol.-%CeO2 doping level. There has been a significant hindrance to grain growth of the YSZ matrix with the increase in CeO2 addition. Thermal conductivity of the sintered composite depends on the doping level of CeO2, temperature and porosity in the sintered composites.Dans cette recherche, on a étudié la fabrication de composites de zircone stabilisée par 8% mol d’oxyde d’yttrium (YSZ), dopé à 5, 10 ou 15% mol d’oxyde de cérium (CeO2) via le frittage au plasma à étincelle. On a suivi l’évolution de phase lors du frittage et l’on a caractérisé la microstructure à l’aide des techniques de la diffraction des rayons x (XRD) et de la microscopie électronique à balayage (MEB). On a étudié la diffusivité thermique des composites en utilisant la méthode du flash laser. Les résultats suggèrent la rétention de la structure cubique de l’YSZ, même avec un niveau de dopage au CeO2 de 15% mol. Il y avait une inhibition significative de la croissance de grain de la matrice de l’YSZ avec l’augmentation du CeO2. La conductivité thermique du composite fritté dépend du niveau de dopage au CeO2, de la température et de la porosité.

Thermophysical and fire properties of vakka natural fiber reinforced polyester composites

Partially biodegradable green composites have been made by incorporating vakka fibers as reinforcement in the polyester matrix. The influence of fiber content and temperature on thermal conductivity, specific heat and thermal diffusivity of composites was investigated. The transverse thermal conductivity of unidirectional composites was investigated experimentally by a guarded heat flow meter method. It was observed that the thermal conductivity of composite decreased with increase in fiber content and at maximum volume fraction of fiber, thermal conductivity of the composites was found to be 0.179 W/m · K. Moreover, the experimental results of thermal conductivity as a function of volume fraction were compared with theoretical model. Thermal conductivity and specific heat capacity of the composite increased with temperature. The lowest thermal diffusivity of 0.55 × 10−7 m2/s for the composite was achieved at a temperature of 120℃. Fire behavior of vakka fiber composite and virgin polyester was investigated using cone calorimeter. The composite ignite earlier and emit lower values of heat release rate and peak heat release rate, when compared to neat polyester resin. Theoretical models were used to predict time to flashover and ignition temperature using cone calorimeter test results as input data.

Thermo physical properties of elephant grass fiber-reinforced polyester composites

The objective of this study is to examine the variation in thermal conductivity, specific heat capacity and thermal diffusivity of composites with respect to fiber content and temperature. The fiber content in the composites was varied from 0.172 to 0.362 by volume. The results revealed that the thermal conductivity of composite decreased with increase in fiber content and the quite opposite trend was observed with respect to temperature. Moreover, the experimental results of thermal conductivity at different volume fractions were compared with theoretical model. The specific heat capacity of the composite with respect to temperature showed similar trend as that of the thermal conductivity. It was observed that the thermal diffusivity of composite was influenced by the fiber content, and the variation of thermal diffusivity with temperature was just opposite to that of thermal conductivity.

Thermal and mechanical properties of waste grass broom fiber-reinforced polyester composites

The main focus of this study is to utilize waste grass broom natural fibers as reinforcement and polyester resin as matrix for making partially biodegradable green composites. Thermal conductivity, specific heat capacity and thermal diffusivity of composites were investigated as a function of fiber content and temperature. The waste grass broom fiber has a tensile strength of 297.58MPa, modulus of 18.28GPa, and an effective density of 864kg/m3. The volume fraction of fibers in the composites was varied from 0.163 to 0.358. Thermal conductivity of unidirectional composites was investigated experimentally by a guarded heat flow meter method. The results show that the thermal conductivity of composite decreased with increase in fiber content and the quite opposite trend was observed with respect to temperature. Moreover, the experimental results of thermal conductivity at different volume fractions were compared with two theoretical models. The specific heat capacity of the composite as measured by differential scanning calorimeter showed similar trend as that of the thermal conductivity. The variation in thermal diffusivity with respect to volume fraction of fiber and temperature was not so significant.The tensile strength and tensile modulus of the composites showed a maximum improvement of 222% and 173%, respectively over pure matrix. The work of fracture of the composites with maximum volume fraction of fibers was found to be 296Jm−1.

Synergistic Effect of Hybrid Filler Contained Composites on Thermal Conductivity

Thermal conductivity of polyetheretherketone (PEEK) with fillers was investigated. By adding the hybrid fillers to polymer the thermal conductivity of composites was increased significantly. Thermal diffusivity of composites was measured using laser flash method. Synergistic filler effect between particulate SiC and carbon fiber (CF) was observed for thermal conductivity. In a PEEK based composite, thermal conductivity increased to 8.25 W/m-K for a 50 vol% hybrid filler (SiC+CF) system, whereas the thermal conductivity of 40 vol% CF was 3.1 W/m-K and 50 vol% of SiC was 2.4 W/m-K, respectively. The use of hybrid filler was found to be effective in increasing thermal conductivity of its composites due to formation of effective thermal conductive path. Experimental results of two-phase system were compared with Nielsen prediction.

Effective thermal diffusivity of composites by the flash method

A theoretical study on the application of the flash method to measure the effective thermal diffusivity of composites made of a matrix filled with aligned fibers or spheres is presented. The lack of adherence between inclusions and matrix has also been accounted for by introducing a thermal contact resistance. From the evolution of the rear surface temperature the thermal properties of the inclusions can be retrieved.

10.4313/TEEM.2013.14.5.231

In this paper, the thermal diffusivity of composites comprising hollow carbon microtube (CMT) filler and unsaturated polyester resin (UPR) have been investigated. The thermal diffusivity of the CMT-UPR composites was increased to 4.056 W/m K at 50 wt% filler loading after reaching a minimum value of about 0.210 W/m K at 1 wt%. At higher filler loading, the mechanical and electrical properties of composites are typically changed. Therefore, the properties of CMT-UPR composites were determined using ASTM methods. The surface and volume-resistivity reach minimum values of 10 7 Ohm/sq and 10 8 Ohm-cm at 50 wt%, and maximum values of 10 17 Ohm/sq and 10 15 Ohm-cm for neat UPR. The distribution of CMTs in the UPR matrix was analyzed by scanning electron microscope (SEM). The thermal behavior of the CMT-UPR composites was determined by differential scanning calorimeter (DSC) and thermal gravimetric analysis (TGA).

The thermal diffusivity of silicon nitride/silicon carbide nanocomposites using a photothermal deflection technique

Measurements are presented to show the effect of mass fraction on thermal diffusivity of composites fabricated from 200 nm silicon carbide particles dispersed in a matrix of silicon nitride. The me...

Solidification of SiC particulate-reinforced aluminum metal matrix composites

Solidification of SiC/A1 particulate-reinforced composite was investigated as a function of volume fraction of particles using the finite element method. The mushy zone effect during solidification was taken into account in the model. Numerical results from the finite element analysis were compared with the analytical solutions using Neumann's method. Based on the study, it was found that numerical results for the unreinforced aluminum A357.0 overestimated solidification time as compared with the analytical solutions, which do not take the mushy zone effect into consideration. As compared with the unreinforced aluminum, composites have a lower solidification rate. In addition, at a lower volume fraction of particles, the effective thermal diffusivity of composite is the dominant factor in determining the solidification time, whereas at a higher volume fraction, the initial thermal energy of composite is the dominant factor.

Thermal Diffusivities of Composites with Various Types of Filler

In-plane and out-of-plane thermal diffusivities (conductivities) of Kerimid resin composites reinforced with various types of filler were studied both experimentally and theoretically. The types of filler used are SiO2 particle, Al2O3 short fiber, Boron Nitride (BN) flake, and Si3N4 whisker. The prediction based on our previous model (Eshelby's equivalent inclusion method) agreed reasonably well with the experiment, except for BN flake composite. It was found that the orientation of filler has a strong effect on the overall thermal conductivity of a composite.

Temperature dependence of thermal conductivities and thermal diffusivities of composites using transient hot-strip method

Simultaneous measurements of the thermal conductivity and thermal diffusivity of four composite building materials, namely black marble stone, normal building stone, red sand brick and cement brick have been made at room temperature using the transient hot-strip method. The power supplied to these samples is quite large compared with that for loose building materials owing to their composite (brick) nature. The temperature dependence of thermal conductivity and thermal diffusivity of these materials has also been investigated in a temperature range from 10 to 60°C. Temperature stability is assured within 0.1°C by using a platinum resistance thermometer in the chamber containing samples and a digital voltmeter to record any variation in resistance. The results of these experiments show that there is a very slight variation in thermal conductivity and thermal diffusivity of these materials in this temperature range.