Boudjemaa Agoudjil

A comparative analysis of dielectric, rheological and thermophysical behaviour of ethylene vinyl acetate/BaTiO3 composites

Dielectric, rheological and thermal behaviours of ethylene vinyl acetate/barium titanate sphere (EVA/BaTiO3) composite materials were investigated in this work. Several composites were prepared for different volume concentrations (from 5% to 49%) and for two types of spheres sizes d: d = 9 µm and d = 105 µm. We show that the use of larger particles allows an increase of dielectric permittivity and thermal conductivity, particularly at high filler concentrations. A comparison between the thermal, dielectric and rheological behaviours of the composites is also reported in this paper. A linear dependence of the relative variation of thermal conductivity and dielectric permittivity, on the one hand, and thermal conductivity and Newtonian viscosity, on the other, was shown.

Transport properties of polyester composite reinforced with treated sisal fibers

Thermal conductivity, diffusivity, relative permittivity, specific heat, and tensile properties of sisal/polyester composites were investigated as a function of fiber volume fraction and fiber surface modification. The composites were prepared by resin transfer molding (RTM) technique. Sisal fibers were subjected to various chemical and physical modifications such as mercerization, heating at 100°C, permanganate treatment, benzoylation, and silanization to improve the interfacial bonding with matrix. All treatments used in this study improved the relative permittivity, tensile strength, Young’s modulus, and reduced the elongation at break. The use of NaOH and silane treatments decreased the thermal conductivity. Beside these, a comparison between dielectric, mechanical, and thermal behaviors of the composites was reported in this paper. A linear dependence of the relative variation of dielectric permittivity, Young’s modulus, and thermal conductivity was also shown for untreated systems.

Numerical modelling of the effective thermal conductivity of heterogeneous materials

The effective thermal conductivity of several series of polymer composite materials constituting two polymeric matrixes: ethylene vinyl acetate (EVA) filled with micrometric particles of barium titanate (BaTiO3) and polypropylene (PP) filled with copper (Cu) particles were investigated. The finite-element software COMSOL 3.5a was used to model the thermal heat transport for an elementary cell in order to estimate the effective thermal conductivity of the composites. The effect of the filler concentrations and the nature of the particles on the effective thermal conductivity were also numerically investigated. The present work compares the numerically calculated and the measured thermal conductivities for various samples.

Thermal Conductivity of Polymer/Carbon Nanotube Composites

As one of the most important field of current nanoscience, the polymer nanocomposites is a promising and efficient way for new generation materials with high performances and multifunctionalities. The incorporating of nanofillers in a polymer matrix may improve mechanical, thermal, electrical or dielectric properties of the composites. The current paper focuses on the thermal conductivity of polymer/carbon nanotube composites. These last, are considered to be ideal candidates for the development of nanocomposite materials. Clarifying the role of the factors, influencing the properties of the composites, enable us to choose the suitable processing method for obtaining the composites and to improve the different properties of these systems. This article reviews the dependence of thermal conductivity of carbon nanotubes on the tube size and the effect of interface on the equivalent property. The relationship between the thermal conductivity and the nanostructure of composites are discussed.

Dielectric and thermophysical properties of Ethylene Vinyl Acetate/BaTiO3 composites

Dielectric and thermal behaviour of Ethylene Vinyl Acetate/Barium Titanate spheres (EVA/BaTiO3) composite materials were investigated in this work. Several composites were prepared for different volume concentration (from 5% to 49%) and for two types of spheres sizes d: d = 9 and d = 105. A simultaneous determination of the thermal conductivity and the diffusivity was achieved using a periodic method. The experimental results of the relative permittivity were obtained from capacitance measurements performed on square plate samples in the frequency range from 103 Hz up to 106 Hz.

Parametric estimation of thermoradiative properties of materials based on harmonic excitation

A simple device for the measurement of emissivity, thermal conductivity, and diffusivity of opaque materials is described. The measurement method is based on the use of a harmonic excitation of a material sample plate. The front surface of the sample is heated periodically and its temperature is measured using a thermocouple. The sample back surface temperature is obtained by infrared thermography. Half of the sample back surface is covered by a black paint of known emissivity used as a reference to compute the sample surface directional emissivity. Thermal conductivity and diffusivity are simultaneously identified from both real and imaginary parts of experimental and theoretical heat transfer functions. Results are presented for a thermally thick sample of PVC, where the sample thickness is greater than the thermal diffusion length. The identified thermophysical properties are in agreement with literature values and reproducible results are obtained. Moreover, some limitations of the method are consider...

A Possible Correlation Investigation between Young's Modulus and Thermal Properties of Green Composites

In this article greencomposites based on gypsum reinforced with date palm fibers (DPF) were fabricated and investigated experimentally in terms of thermal and mechanical properties. This paper deals with two aspects, the first one is a study on the influence of fibers sizes and content on thermal diffusivity and Young’s modulus of date palm fibers (DPF) reinforced gypsum composite. The second one is an experimental correlation investigation between Young’s modulus and thermal properties (thermal conductivity, thermal diffusivity). According to the results of this study, the Young’s modulus and the thermal diffusivity of the greencomposites is mainly influenced by the interfacial adhesion between the matrix and fibers. The experimental correlation between Young’s modulus and thermal properties shows variant results.