*5.3. Thermal Response of the Corrugated Core ITPS*

While the focus of this work aims at comparing ablative TPS with a novel ITPS based on metallic lattice core sandwich structures with PCMs embedded, the comparison with CMC-based corrugated ITPS is useful, as this technology is established in the literature. The considered structural material is an existing C/SiC composite obtained via chemical vapour infiltration whose properties are homogenised based on [10]. The thermal conductivity parallel to the fibre orientation is considered on the webs, whereas the one orthogonal to the fibre is considered for the face sheets. The filling material considered is the Saffil® fibrous insulation felt.

The SLSQP optimisation algorithm described in Section 3 is used to obtain the geometrical parameters of the component, which are reported in Table 3. The obtained overall areal weight is 23.7 kg/m2. Figure 11 shows the temperature evolution under the same boundary conditions previously analysed. It can be noticed that a thermal gradient of 1100 K is present between the top face sheet and the bottom face sheet. This indicates that the optimisation reached its goals, achieving a component with a very low effective thermal diffusivity. This allows the re-radiation of a wide amount of the convective heat input. This

design is beneficial from the thermal protection design point of view. However, due to the combination of high stiffness of C/SiC and high thermal gradient, thermo-mechanical stresses can become a concern, given the low specific strength of CMCs.

**Table 3.** Optimized geometric parameters for the corrugated core ITPS.


**Figure 11.** Temperature evolution at different points in the out-of-plane direction (z) for the optimised CMC-based corrugated core ITPS.
