In this study, we develop and characterize an asbestos-free rubber composite for potential use as a rocket motor insulator. The insulator is based on ethylene propylene diene monomer blended with aramid fiber (Kevlar) in the pulp form (KP), together with alumina and/or silica as reinforcement. Different formulations based on these fillers were prepared. The fillers were dispersed in the ethylene propylene diene monomer polymeric matrix to obtain a homogenous master batch for curing. We analyzed and compared physical, mechanical and thermal properties of different compositions (density, hardness, tensile strength, elongation, ablation resistance and mass loss on heating). Reinforcement of ethylene propylene diene monomer with Kevlar improves the performance of the material with respect to mechanical and thermal properties, while not improving well the performance with respect to ablation resistance. Using hybrid reinforcement (KP + alumina + silica) within ethylene propylene diene monomer improves the performance of ethylene propylene diene monomer with respect to mechanical properties, thermal properties, ablation resistance and thermal decomposition resistance. The optimum performance of the insulation material was achieved when the formulation consisted of 10 part per hundred ratio KP with even amounts of alumina and silica. A novel composite engineered for improved insulation of solid rocket motors using the hybrid reinforcements was developed for the first time, which can be applied in future space missions.