INVESTIGATION OF THERMAL CONDUCTIVITY OF LUFFA AND LUFFA-COIR REINFORCED EPOXY COMPOSITES

Thermal behavior of luffa and coir reinforced epoxy composites have been evaluated for a constant total fiber volume fraction 0.4Vf by varying the ratio of luffa and coir fiber. Thermal conductivity of luffa-epoxy and luffa-coir reinforced epoxy composite was studied experimentally and analytically in terms of fiber size and fiber volume. Thermal conductivity of composites was investigated experimentally by a guarded heat flow meter method. The experimental results at different volume fraction were compared with three theoretical models. The composite C has the lowest thermal conductivity of 0.206 W/mk with 0.81 % of voids. The experimental values of thermal conductivity of hybrid composites are the good correlation with the Maxwell and Maxwell-Eucken models. As in a case of 0.4 Vf of luffa-epoxy composites these values are closer to the rule of mixture models. The thermal stability of the composites was investigated by thermogravimetric analysis. This result reveals that the hybridization of luffa and coir with epoxy allows a significantly improved insulation ability of the composites.

Heat Dissipation in Epoxy/Amine-Based Gradient Composites with Alumina Particles: A Critical Evaluation of Thermal Conductivity Measurements

For the design of the next generation of microelectronic packages, thermal management is one of the key aspects and must be met by the development of polymers with enhanced thermal conductivity. While all polymer classes show a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers, yielding polymer-based composite materials with high thermal conductivity. The inorganic fillers, however, are often available only in submicron- and micron-scaled dimensions and, consequently, can sediment during the curing reaction of the polymer matrix. In this study, an epoxy/amine resin was filled with nano- and submicron-scaled alumina particles, yielding a gradient composite. It was found that the thermal conductivity according to laser flash analysis of a sliced specimen ranged from 0.25 to 0.45 W·m−1·K−1 at room temperature. If the thermal conductivity of an uncut specimen was measured with a guarded heat flow meter, the ‘averaged’ thermal conductivity was measured to be only 0.25 W·m−1·K−1. Finite element analysis revealed that the heat dissipation through a gradient composite was of intermediate speed in comparison with homogeneous composites exhibiting a non-gradient thermal conductivity of 0.25 and 0.45 W·m−1·K−1.

Processing and Thermal Conductivity Characterization of Solid Glass Micro-Spheres Filled Polymer Composites

This paper describes the preparation and thermal conductivity characterization of solid glass micro-spheres (SGMs) filled polymer composites. SGMs of different sizes are embedded in epoxy resin to develop composites by hand layup technique. A numerical simulation of the heat-transfer within the composites is made by using finite element method (FEM). Three-dimensional spheres-in-cube lattice array models are constructed to simulate the microstructure of composite materials for various SGM content ranging from 0 to about 27 vol % and the effective thermal conductivities (Keff) of the composites are estimated. Keff values are also calculated using some of the existing theoretical models. Finally, guarded heat flow meter test method is used to measure the conductivity of these composites. The simulations are compared with Keff values obtained from experiments and it is found that the FEM simulations are fairly close to the measured Keff. This study shows that the incorporation of SGMs results in reduction of conductivity of epoxy resin and thereby improves its thermal insulation capability. Further, the size and content of SGMs influence the extent of reduction of Keff. Keywords: Composites; Glass Microspheres; FEM; Thermal Conductivity; Simulation