Ablative properties and mechanisms of hot vulcanised silicone rubber (HVSR) composites containing different fillers

Hot vulcanised silicone rubber (HVSR) composites were prepared using silicon carbide (SiC), hafnium oxide (HfO2), zirconium oxide (ZrO2) and zirconium boride (ZrB2) as fillers, respectively. The tensile properties and the ablative response of the composites were examined. Tensile tests indicated that the tensile strength of HVSR was increased by the incorporation of ZrB2. The linear ablation rate of the composites increased in the order HVSR/ZrB2 < HVSR/ZrO2 < HVSR/SiC < HVSR/HfO2 < blank HVSR. The maximum back-face temperatures of the composites acquired from the burnt specimens during the ablation test were 350 and 364 K for the HVSR/ZrB2 and HVSR/ZrO2, respectively, compared to that of 333 K for the blank HVSR. Scanning electron microscopy and X-ray diffraction results showed that the dense and rigid ceramic layer was hard to peel off under the high pressure and shearing forces of ablative gases. The HVSR/ZrB2 specimens exhibited the best ablation resistance among all the composites involved in this work.