Thermoelastic anisotropy of a natural fiber

In order to develop structure–property relationships in composite systems, it is often necessary to know the properties of the fiber and matrix constituents. Much research indicates that natural-fibers exhibit a complicated anisotropic structure. Unfortunately, the property anisotropy of most natural fibers has been left undetermined. In this study, dynamic mechanical and thermal mechanical techniques have been employed to measure the elastic and thermal expansion characteristics of a model composite system containing jute fibers over a broad temperature range. The results of these measurements were in turn incorporated into a number of pertinent micro-mechanical models to estimate the thermoelastic properties of the natural fibers. The jute fibers investigated in this study exhibited considerable elastic and thermal expansion anisotropy. The longitudinal Young’s modulus of the fibers has been determined to exceed the transverse fiber modulus by as much as an order of magnitude in certain temperature regimes. The fibers exhibit negative thermal expansion coefficients along their lengths; however, large positive thermal expansion coefficients, similar in magnitude to many polymeric materials, have been estimated in the transverse directions.