A hybrid multiscale approach to the thermal conductivity of 3D woven composites with porous ceramic matrix

3D woven composites with porous ceramic matrix, distinguished by their high-temperature resistance, light weight, and high stiffness, offer considerable potential for applications in thermal protection systems and aeroengine hot-section components. Inaccurate evaluation of their thermal properties may introduce risks in assessing thermal behavior under varying conditions. However, the existing predictive models mainly focus on plain-woven composites, often neglect interfacial thermal resistance, and rely on numerical methods that can be computationally demanding across scales. Thus, this study aims to propose an efficient hybrid method to evaluate the effective thermal conductivity of 3D woven composites with porous ceramic matrix. A multiscale modeling framework was established for the thermal conductivity across three length scales, namely the micro scale (for matrix with pores), the meso scale (for woven yarns), and the macro scale (for the composite). Theoretical models based on effective medium theory using the Maxwell far-field matching method were derived for the matrix and yarns, while a Micro-CT-based representative volume element incorporating interfacial thermal resistance was used for finite element analysis at the macro scale. This approach is applied to a 3D woven Al 2 O 3 /SiO 2 composite with porous matrix. The predicted thermal conductivity shows good agreement with experiments, with deviations within 20% when interfacial effects are included, while neglecting them leads to overestimation of up to 58%. The influences of porosity, pore shape, and fiber volume fraction on the effective thermal conductivity were further explored across various scales. For the overall composites, increasing porosity reduces the thermal conductivity by approximately 30%, while variations in fiber volume fraction lead to changes of up to 74%.