Establishment of strain rate‐dependent intrinsic models for short‐cut carbon fiber/nitrile composites in different pyrolysis states

Abstract Flexible nozzle extension technology has been extensively researched throughout the world, but traditional materials cannot meet the growing demands in harsh environments. Short‐cut carbon fiber‐reinforced nitrile rubber (CF/NBR) composites, which are similar to the phenolic impregnated carbon ablator, are currently a hot research topic in this field. The mechanical properties of CF/NBR composites were experimentally tested to study the change in the mechanical behavior of a rocket engine's flexible nozzle extension section under thermal coupling. As indicated by the results, existing models cannot accurately predict changes in materials' mechanical behavior. The theoretical foundation of the nonlinear viscoelastic intrinsic model of rubber is utilized. The uniaxial tensile intrinsic model of CF/NBR composites has been improved by introducing physical parameters, such as fiber reinforcement, strain rate‐dependent correction and temperature‐dependent correction coefficients, and fiber volume fraction. Results show that the intrinsic model developed in this article provides a guide to the uniaxial tensile mechanical behavior of randomly distributed short‐cut CF/NBR composites with known mass‐part formulations and fiber volume fractions at room temperature and under different pyrolysis conditions.