A computing method on equivalent thermal conductivity of plain braided C/SiC composites material was proposed based on finite element method. Mesoscopic structure of materials was studied firstly

including microscopic model of carbon fiber bundles with matrix and single-cell model. Effects of porosity on the matrix equivalent thermal conductivity coefficient were calculated using random-pore single-cell model. The equivalent thermal conductivity coefficient of carbon fiber bundles with matrix and composites material was calculated under the condition of three sets of boundary conditions. Finally with the proposed method

the relationship between equivalent thermal conductivity coefficient and fiber volume fraction/porosity was studied in detail. The results indicate that the equivalent thermal conductivity coefficient of the composites material decreases linearly with the increase of fiber volume fraction. While fiber volume fraction increases from 54% to 78%

the equivalent thermal conductivity coefficient in y axis direction declines by 12.8% and that in x and z axis directions by 8.6%. The equivalent thermal conductivity coefficient of the composites material presents an accelerating downward trend during the porosity's rising process. While the porosity increases from 0% to 30%

the equivalent thermal conductivity coefficient declines by 22.91% in x and z axis directions and 34.66% in y axis direction.