Numerical study on thermal conductivities of spread tow woven pierced composites

Textile reinforced composites are extensively used in thermal protection engineering because of their outstanding mechanical and physical properties. Spread tow woven pierced composites (STWPs) are composed of fiber rods, a spread tow and a matrix with small air pores. In the experiment, the STWPs displayed improved thermal conductivities compared with traditional woven composites. Thermal conductivities in the in-plane and out-of-plane directions have increments of 18.7% and 16.7%, respectively. This is mainly attributed to the influence of the fiber volume fraction. Herein, three numerical models were constructed to predict the thermal conductivities of the matrix, spread tow and fiber rods, and as the input parameter of the mesoscale model. The curvature of the interlaced tow in the mesoscale model was defined considering that the spread tow is extremely light and thin. The predicted results are in accordance with the experimental results, with only 8.13% and 8.94% errors in the in-plane and out-of-plane directions, respectively, indicating that the numerical models are accurate and effective. In addition, the thermal conductivities of STWPs decrease with the increase of porosity, but increase with the increment in fiber volume fraction and interphase thermal conductance. This work can provide effective guidance for the thermal design of STWPs.