Thermal diffusivity of carbon/phenolic composites exposed to harsh hyperthermal environments: theoretical assessment and experimental protocol

Carbon/Phenolic Composites (CPCs) are essential to manufacture many portions of the nozzle assembly of Solid Rocket Motors (SRMs) which are essential both to preserve an independent and responsive access to space as well as for homeland security. In current research, in terms of heat transfer analysis, starting from the assumption of one-dimensional (1D) semi-infinite solid, the analytical solutions of certain selected hyperthermal heating scenarios will be presented, and criteria will be given for their use in solving ablation problems. From the assumption of constant thermo-physical properties, an approach permitting the exact solution of a 1D unsteady heat conduction problem involving variable thermal properties, was introduced and tested for CPCs. Starting from these theoretical results, a method aimed at preliminary retrieving the in-plane and out-plane thermal diffusivity of CPCs through the Oxy-Acetylene Torch (OAT) tests was validated. The proposed approach showed to be effective especially in terms of capability to determine the thermal diffusivity of CPCs at high heating rates. A comprehensive work of comparison of the obtained data with state-of-the-art CPCs such as MX-4926 and FM-5014 was carried out. The proposed protocol can be used not only with hyperthermal sources such as torches, but it can also be extended to other heating devices such as electrical or induction heaters.