This article presents a new application of two-scale asymptotic homogeni zation schemes to predict the orthotropic thermal conductivity of plain-weave fabric rein forced composite laminates. A unit-cell, enclosing the characteristic periodic repeat pat tern in the fabric weave, is isolated and modeled. A new three-dimensional series-parallel thermal resistance network is developed to solve a steady-state heat transfer boundary value problem (BVP) for this unit-cell. Laminate effective orthotropic thermal conduc tivities are obtained analytically and numerically as functions of (1) thermal conductivity of the constituent materials, (2) fiber volume fraction, and (3) weave style. The analyti cally predicted thermal conductivity values are compared with numerical finite element predictions, with existing models in the literature and with experimentally obtained values.
Thermal properties, such as thermal conductivity, thermal diffusivity, and specific heat, of treated and untreated oil palm fiber-reinforced PF composites were measured simultaneously at room temperature and normal pressure using the transient plane source (TPS) technique. An increase in thermal conductivity was observed in the fiber-treated and resin-treated composites. Surface modifications of fibers by prealkali, potassium permanganate, and peroxide treatments increased the fiber-matrix adhesion by increasing porosity and pore size of the fiber surfaces. The increase in crosslinking enhanced the thermal conductivity of a composite of resin treated with peroxide compared to other composites. Also an attempt was made to explain the temperature dependence of thermal conductivity and thermal diffusivity of amorphous polymer samples using the same technique. It was observed that at the glass-transition peak of the polymer, thermal conductivity and diffusivity were maximum. Below and above this temperature their values decreased. This has been explained on the basis of predominant scattering processes. An empirical relationship was established for the theoretical prediction of thermal conductivity and diffusivity.
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