Modeling of Thermal Conductivity of CVI-Densified Composites at Fiber and Bundle Level

Abstract

The evolution of the thermal conductivities of the unidirectional, 2D woven and 3D braided composites during the CVI (chemical vapor infiltration) process have been numerically studied by the finite element method. The results show that the dual-scale pores play an important role in the thermal conduction of the CVI-densified composites. According to our results, two thermal conductivity models applicable for CVI process have been developed. The sensitivity analysis demonstrates the parameter with the most influence on the CVI-densified composites’ thermal conductivity is matrix cracking’s density, followed by volume fraction of the bundle and thermal conductance of the matrix cracks, finally by micro-porosity inside the bundles and macro-porosity between the bundles. The obtained results are well consistent with the reported data, thus our models could be useful for designing the processing and performance of the CVI-densified composites.

Thermal Characterization of Carbon Fiber-Reinforced Carbon Composites

“…One way to determine and to distinguish the effect of components in the C/C composite (carbon fibers and matrix), is by obtaining the thermal conductivity of samples of pure matrix (without carbon fibers). A good approximation to thermal behavior of the pure matrix is to consider it as glasslike carbon (GC) material [31], then the effective thermal conductivity of the matrix (κ me ) can be expressed by: κ me = ξκ GC , where ξ is a constant that depends on volume fraction of solid matrix and porous, as well as the pore shape factor [81]. Effective thermal conductivity of the matrix out of plane can be expressed as [50]:…”