THEORETICAL AND EXPERIMENTAL INVESTIGATIONS ON THE DIFFUSIVITIES OF COMPOSITES

Abstract

Dealing with the tailoring of thermo-hygro-elastic (THE) composites the powerful tool of anisotropy is multiplied by taking into account the crosscoupling effects (Soret and Dufour) of heat conduction (Fourier) and moisture diffusion (Fick). In this case four diffusivities arise (k/pc, dm , d'!:t, dP), which are somehow related depending all of them on the microstructure of material, but the two latter ones are equal according to the Onsager's relations. Based on our previous investigations [1, 2] we introduced the governing equations of the problem and solved them numerically for 1D with given initial and boundary con- ditions. With a special definition of the coupled coefficient of thermal/moisture expansion (CT /ME), we got the displacement (L( t)) and temperature (TL( t)) versus time at the end of the rod. The experiment was performed with a rod type specimen made of heat conducting and moisture absorbing composite matrix material. The conditions modelled thermal shock, perfect insulation and different moisture content. The comparison of the numerical and experimental values of L(t) and TL( t) enables us to conclude to the diffusivities. Comparing with values of literature [3, 4] we have certain hope to separate the different diffusivities.