Abstract
A skin structure for thermal protection is one of the most interesting components that needs to be considered in the design of a hypersonic vehicle. The thermal protection structure, if a dense structure is used, is heavy and has a large heat conduction path. Thus, a lightweight, high strength structure is preferable. Currently, for designing a lightweight structure with high strength, natural materials are of great interest for achieving low density, high strength, and toughness. This paper presents bio-inspired lightweight structures that ensure high strength for a thermal protection system (TPS). A sinusoidal shape inspired by the microstructure of the dactyl club of Odontodactylus scyllarus, known as the peacock mantis shrimp, is presented with two different geometries, a unidirectionally corrugated core sandwich structure (UCS) and a bidirectionally corrugated core sandwich structure (BCS). Thermomechanical analysis of the two corrugated core structures is performed under simulated aerodynamic heating, and the total deflection and thermal stress are presented. The maximum deflection of the present sandwich structure throughout a mission flight was 1.74 mm for the UCS and 2.04 mm for the BCS. Compared with the dense structure used for the skin structure of the TPS, the bio-inspired corrugated core sandwich structures achieved about a 65% weight reduction, while the deflections still satisfied the limits for delaying the hypersonic boundary layer transition. Moreover, we first fabricated the BCS to test the thermomechanical behaviors under a thermal load. Finally, we examined the influence of the core thickness, face-sheet thickness, and emittance in the simulation model to identify appropriate structural parameters in the TPS optimization. The present corrugated core sandwich structures could be employed as a skin structure for metallic TPS panels instead of the honeycomb sandwich structure.
Highlights
A thermal protection system (TPS) is required to be lightweight, provide high strength under dynamic and acoustic pressures, and withstand aerodynamic heating during hypersonic flight
Even though the boundary conditions were different from the real condition and the tests were performed in room conditions for the test structure, we expected that the results from the experiment would provide precise knowledge of the thermomechanical responses of the bidirectionally corrugated core sandwich structures before they would be employed in the TPS panel
Because a high stress and large deflection were found in the sandwich structures made of stainless steel under a high heating rate and a prototype of the TPS panel with the stainless steel bidirectionally corrugated core sandwich structure (BCS) for future testing was available, we investigated the influence of the core thickness, face-sheet thickness, and emittance on the thermomechanical performance of the sandwich structures made of stainless steel under a high heating rate in order to prevent possible failure in the TPS panel
Summary
A thermal protection system (TPS) is required to be lightweight, provide high strength under dynamic and acoustic pressures, and withstand aerodynamic heating during hypersonic flight. Most of the research focused on the goal of the temperature limit in the internal structure of the vehicle, and they determined the proper thickness and material for the TPS panel [11,14,15,16] They investigated whether the residual stress in the TPS panel remained at high levels [17]. The use of the bio-inspired corrugated core sandwich structure under extreme thermal loads is very rare and thermomechanical characteristics have not been identified yet To address these challenges, we proposed a modified design of a bio-inspired sinusoidal corrugated core sandwich structures and investigated their thermomechanical performance under high-temperature conditions. This paper aims to propose the corrugated core sandwich structure panel to reduce the weight and guarantee the strength for the TPS panel under high-temperature conditions. (a) Odontodactylus scyllarus mantis shrimp with the dactyl club marked in red, (b) the dactyl club was separated from the body, (c) a computerized tomography scan of the section, (d) microstructure of the impact region, (e) higher magnification of the impact region showing the sinusoidal shape, (f) a three-dimensional model of the sinusoidal shape
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