Numerical Investigation of Characteristic of Anisotropic Thermal Conductivity of Natural Fiber Bundle with Numbered Lumens

Guan-Yu Zheng

doi:10.1155/2014/506818

Abstract

Natural fiber bundle like hemp fiber bundle usually includes many small lumens embedded in solid region; thus, it can present lower thermal conduction than that of conventional fibers. In the paper, characteristic of anisotropic transverse thermal conductivity of unidirectional natural hemp fiber bundle was numerically studied to determine the dependence of overall thermal property of the fiber bundle on that of the solid region phase. In order to efficiently predict its thermal property, the fiber bundle was embedded into an imaginary matrix to form a unit composite cell consisting of the matrix and the fiber bundle. Equally, another unit composite cell including an equivalent solid fiber was established to present the homogenization of the fiber bundle. Next, finite element thermal analysis implemented by ABAQUS was conducted in the two established composite cells by applying proper thermal boundary conditions along the boundary of unit cell, and influences of the solid region phase and the equivalent solid fiber on the composites were investigated, respectively. Subsequently, an optional relationship of thermal conductivities of the natural fiber bundle and the solid region was obtained by curve fitting technique. Finally, numerical results from the obtained fitted curves were compared with the analytic Hasselman-Johnson’s results and others to verify the present numerical model.

Highlights

Natural fibers like kenaf fiber [1], hemp fiber [2], sisal fiber [3], date palm fiber [4], wood fiber [5], and bamboo fiber [6] have unique advantages of low density, high specific properties, biodegradable nature, and low cost; composites filled with natural fibers, such as natural fiber reinforced polymer/cement composites, are usually viewed as green and environmentally friendly composites and have attracted much attention of researchers for potential engineering application
The fiber bundle is assumed to be embedded into a matrix with known thermal conductivity to construct unit composite cell, which is numerically analyzed by applying proper thermal boundary conditions along the cell boundary
A homogenized composite model is constructed, in which the fiber bundle is replaced by an equivalent solid fiber to investigate the influence of the homogenized fiber bundle

Summary

Introduction

Natural fibers like kenaf fiber [1], hemp fiber [2], sisal fiber [3], date palm fiber [4], wood fiber [5], and bamboo fiber [6] have unique advantages of low density, high specific properties, biodegradable nature, and low cost; composites filled with natural fibers, such as natural fiber reinforced polymer/cement composites, are usually viewed as green and environmentally friendly composites and have attracted much attention of researchers for potential engineering application. As one of inherent material properties of natural fibers, thermal property of natural fibers is of great importance in natural fiber reinforced composites, due to inherent hollow microstructure of natural fibers. Liu et al evaluated the transverse thermal conductivity of Manila hemp fiber in solid region by the finite element method and analytical Hasselman-Johnson’s model [2]. They studied the effect of the microstructure of natural fiber on the transverse thermal conductivity of unidirectional composite with abaca and bamboo fibers, by experiment and finite element simulation [9]. Behzad and Sain predicted the thermal conductivity for hemp fiber reinforced composites by experimental measurement [10], and subsequently they developed a finite element

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Conclusion