Constructing layered structure improves thermal protection performance of silicone rubber-based composites under coupled mechanical-thermal-oxidative conditions

The ablative properties of silicone rubbers significantly deteriorate under coupled mechanical-thermal-oxidative conditions, which limits their application in aerospace and fire protection sectors. In this work, the ablative behavior of silicone rubbers with different molecular chain structure was comparatively studied. Based on the above preliminary screening trials, vinyl methyl silicone rubber-based composite (VMQ-c) exhibited superior thermal insulation performance due to the formation of rich porous structure in char layer, and phenyl silicone rubber-based composite (PVMQ-c) formed a more stable and intact char layer which could withstand external scouring heat flows. As a result, a layered structure was proposed to combine VMQ-c with PVMQ-c to synergistically improve ablative performance. The results showed that the mass ablative rate of samples with layered structure was 0.0548 g/s under the conditions of 1 MW/m², 10 % tensile strain and 20 s, which is 27.9 % lower than VMQ-c and 13.8 % lower than PVMQ-c. Meanwhile, the maximum back-face temperature was 182.4°C for a 3 mm thick sample, which confirms exceptional thermal insulation performance of the proposed structure for thermal protection purpose under harsh conditions.