Influence of pore morphology on thermo-mechanical response of ceramic matrix composite plates

Ceramic matrix composites (CMCs) are promising candidates for next-generation aero-engine hot-section components due to high-temperature capability and low density relative to nickel-based superalloys. Pores in CMCs are introduced during manufacturing due to incomplete densification, thermal expansion mismatch between fibers and matrix, and the deliberate incorporation of porous interphases to enhance toughness. However, fabrication-induced porosity remains a critical factor limiting thermo-mechanical reliability. This study reconstructs micro- and meso‑scale representative volume elements (RVEs) from 3D X-ray computed tomography of actual CMC plates and blades to quantify the influence of pore morphology under fixed porosity conditions (5–15%) using coupled thermo-mechanical simulations. Results show that pore morphology induces <10% variation in effective thermal conductivity across both scales, confirming its negligible role in bulk thermal transport. In contrast, irregular morphologies significantly elevate local temperature gradients—reaching up to 45,000 K/m (137% higher than spherical pores)—with pronounced concentrations at geometric discontinuities such as edges, corners, and termini. These extreme gradients govern thermal stress concentrations, elevating peak stresses to approximately 60 MPa. A direct spatial correlation is established between perturbed thermal conduction paths around complex pore geometries and the resulting stress hotspots. Critically, strategic tailoring of pore architecture to suppress these extremes reduces peak thermal stress by 37%, thereby extending the service life of exhaust nozzle flaps by 10–20% during engine start-up transients. These findings provide actionable design guidelines for enhancing the thermo-mechanical durability of CMC components in aerospace propulsion systems.