<報文>非定常法による複合材料の有効熱伝導率導出に関する数値シミュレーション

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A Laser flash technique has frequently used for the thermal diffusivity measurements of various materials. However the apparent thermal diffusivity of composite materials measured by the transient method including the laser flash technique may not be equal to the effective thermal conductivity defined under the steady heat flow condition. The main purpose of this paper is to obtain the information about the relation between the effective thermal diffusivity for a composite system and the apparent thermal conductivity derived from the measured temperature response curve measured by the transient method, as a function of a dispersed phase, its volume fraction to the matrix. Here, the fibrous composites are tested as an example of composite materials. The temperature responses for the model of the simple fibrous composite were calculated under both the steady and unsteady heat flow conditions by using the finite element method (FEM). The calculation was made in the following cases; (1) Ratio of the thermal conductivity of fiber to the thermal conductivity of matrix : 0.01,0.1,1,10,100,(2) Number of fibers : 1,2,4,8,(3) Volume fraction of fiber in matrix : 0.04,0.12,0.24,0.4. The effective thermal conductivity (λ_e) of a model system was estimated from the integration of heat flux on the surface under the steady heat flow condition. On the other hand, the apparent thermal diffusivity of a model (α_a) was determined from the temperature response at the back surface of a sample after flashing a heat pulse on the front surface. Then, the apparent thermal conductivity (λ_a) of a model was estimated. In the cases of a system including 1 or 2 fibers, λ_a shows the significant difference from λ_e. However, λ_a agrees well with λ_e, when the number of fibers increases to 4 or 8. This result clearly suggests that as far as the number of fibers in the sample is more than 4,the effective thermal conductivity value is sufficiently consistent with that determined by the usual laser flash technique. Although this conclusion should be given with respect to the conditions presently investigated, the laser flash technique is considered to be one of the powerful methods for determining the thermal properties of fibrous and other composites.effective thermal conductivityapparent thermal conductivitylaser flash techniquefibrous compositesstcady flow conditionunsteady flow conditionfinite element method
東北大学の論文
1994-03-30

<報文>非定常法による複合材料の有効熱伝導率導出に関する数値シミュレーション

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