Design Of Lightweight Cellular Core Sandwich Panels For Integrated Thermal Protection System

As the hypersonic vehicles are flying at supersonic speed,the out surface of the vehicle’s body will be subjected to severe aerodynamic heating loads,resulting in a rapid increase in the temperature of the vehicles body and even the risk of ablation.Thus,the thermal protection systems(TPS)as an important part of the hypersonic vehicles,are designed to protect the internal components of the vehicle at a safe temperature and ensure that the shape of the vehicles does not change significantly.Thus,the TPS has an important impact on the overall performance of the vehicle.The integrated thermal protection system(ITPS)is an important development direction of the TPS,since it has both thermal insulation and load-bearing functions.The ITPS with light-weight lattice sandwich structure has light weight,excellent mechanical properties and good heat insulation effect.Nowadays,the ITPS has received extensive attention and research.Current ITPS are mainly used the high-temperature alloy materials,which have low service temperature and are prone to structural failure at high temperatures.The previous work apparently show that compared with ITPS using metalsandwich panels,ITPS incorporating ceramic matrix composites(CMC)sandwich panels gives remarkable advantages of high temperature resistance and low areal density.At the same time,due to the complexity of the cellular core sandwich structure,the research on the heat transfer mechanism and the theoretical exploration of the equivalent thermal conductivity of the cellular core sandwich panels is still imperfect,especially for the more complex body-centered cubic cellular sandwich panels.In addition,most of the ITPSs were designed with one single layer of the sandwich panel,resulting in an inevitable thermal short effect,especially for the ITPS with corrugated core sandwich panel,and this type design will introducing high risk of buckling failure under the action of aerodynamic loads.In this paper,the heat transfer mechanism and thermal insulation performance of lightweight cellular core sandwich panels are analyzed by establishing the heat transfer models and numerical simulation.Firstly,the heat transfer mechanism of the high temperature ceramic corrugated sandwich panels are analyzed and discussed in Section 2,and the influence of thermal insulation materials on the heat transfer mechanism of the corrugated sandwich panels is studied.The results confirmed thatthe cavity radiation can be fully blocked by the insulation materials,and it can remarkably enhance the insulation efficiency and improve the temperature uniformity.Secondly,the relative density of the corrugated sandwich panels is relatively large,and the lightweight characteristic of the lattice core sandwich panels show obvious advantages.Thus,the heat transfer mechanism of the lattice core sandwich panels is studied in Section 3,and the theoretical formula of the effective thermal conductivity is established,which provides a fast and reliable theoretical analysis for the thermal insulation performance of the lattice core sandwich panels.Then,motivated by improving both thermal insulation effect and structural robustness of the CMC ITPS,design and analysis of multi kinds of insulation materials filled in the core of ITPS with certain graded patterns are discussed in Section 4,and the CMC ITPS comprised of multi layers of sandwich panels is also proposed.Finally,this paper proves that the CMC lattice core sandwich panels,combine with the graded insulation materials design can reduce the maximum temperature on the bottom facesheets,and the multilayer sandwich panels in ITPS can suppress the thermal short effect.Besides,the multilayer sandwich panels also enhance the buckling strength.The research work in this paper provides an important basis for the design and analysis of the ITPS.