RÉSUMÉ

The details of the burning surface layer can have a great influence on the combustion performance of solid fuels for hybrid propulsion. In composite solid fuels, a substance with a low decomposition temperature or a fast burning rate leaves holes in the initial matrix after decomposition or burning, thus increasing the regressing surface area. Azodicarbonamide (ADCA)/hydroxyl-terminated polybutadiene (HTPB) composite fuels can achieve this kind of mechanism: ADCA decomposes at the temperature of 150–306°C while HTPB decomposes at 417–591°C, thus forming a certain thickness of porous layer after the decomposition of ADCA particles when the fuel burns. However, the gaseous products increase the blocking effect, hindering heat transfer from the flame zone to the fuel surface and suppressing combustion. In this study, we investigate the effects of ADCA on the combustion characteristics of HTPB-based composite solid fuels. The first exothermic peak of thermal gravimetry and differential scanning calorimetry (TG-DSC) tests for ADCA/HTPB fuels decreases, while the second exothermic peak increases in intensity and simultaneously shifts to lower temperatures with increasing ADCA contents. The optimal addition to the HTPB matrix of 3% in mass of ADCA particles enhanced the pre-expansion during combustion and showed an increased regression rate by 41.52%, while 1% and 5% in mass of ADCA increased by 2.99% and –0.40%, respectively, at G_OX = 340 kg/m²s, but revealed a decrease to –15.61%, –11.81%, and –25.74%, correspondingly at G_OX = 150 kg/m²s. This suggests that appropriate ADCA acts as an effective burning rate modifier by favoring the formation of a certain thickness of porous layer.