Study on Low-Velocity Impact Performance of Coal-Based Carbon Foam Sandwich Structures in Thermal Protection Systems

Coal-based carbon foam (CCF) has been widely used in the hypersonic vehicles’ thermal protection system (TPS) due to its good thermal insulation and mechanical properties. In addition, CCF can absorb large quantities of energy when crushed so that the CCF sandwich structure can effectively improve the impact resistance of the TPS. However, there are few studies on the impact performance of CCF sandwich structures, even the mechanical constitutive model (MCM) of CCF. This research work built the CCF MCM and studied the low-velocity impact properties. A large number of experiments were implemented to establish an effective and comprehensive CCF MCM which has three parts: basic mechanical properties, multiaxial loading failure criteria, and hardening rules. A series of tests on the low-velocity impact performance of two CCF sandwich structures were carried out, and finite element models (FEMs) were established according to the CCF MCM to simulate these tests. The experimental and simulation results were in good agreement. The impact damage mechanism was revealed by the tests and the FEMs. The MCM can be used not only for the simulation of low-velocity impact process but also for failure analysis of other CCF structures, which will help to design CCF structures at a low cost.