Contents lists available at ScienceDirect International Journal of Thermal Sciences journal homepage: www.elsevier.com/locate/ijts Thermal and thermomechanical performance of actively cooled pyramidal sandwich panels Jingzhe Xie a,b , Ruiping Zhang b , Gongnan Xie a,d,∗ , Oronzio Manca c a School of Marine Science and Technology, Northwestern Polytechnical University, Box 24, Xi'an, 710072, China b School of Mechanical Engineering, Northwestern Polytechnical University, Box 552, Xi'an, 710072, China c Dipartimento di Ingegneria Industriale e dell'Informazione, Universita' degli Studi della Campania Luigi Vanvitelli, Via Roma 29, Aversa (CE) 81031, Italy d Research & Development Institute of Northwestern Polytechnical University in Shenzhen, Shenzhen, 518057, Guangdong, China ARTICLE INFO Keywords: Pyramidal sandwich panels Actively cooled Thermal performance Thermomechanical performance Convection flow Aerodynamic heating ABSTRACT Previous research has proved that pyramidal core sandwich panel is an excellent kind of passive Thermal Protection Systems (TPSs) for hypersonic aerospace aircrafts suffered from in-service environment. To explore its further insulation performance and load-bearing capability, four kinds of actively cooled pyramidal core sandwich panels are designed and investigated in this paper. Convection flow mechanism for cooling channels is described in details. Influences of the coolant velocity, channel height ratio and flow direction of the two layers on thermal performance are firstly studied and discussed in an appropriate way. Analysis of thermomechanical performance is then performed. The effect of the cover board thickness on thermomechanical performance is also studied. In consequence, a light-weight, structural and thermal integrated thermal protection system (ITPS) has been designed to protect hypersonic aircrafts from intense radiation heat flux in service. 1. Introduction The hypersonic aircrafts have a trend of becoming lightweight and faster, which commonly suffer a harsh and complex environment. Heat dissipation problem for the thermal protection system (TPS) has drawn a wide attention. To achieve a successful hypersonic flight, TPSs on reusable launch vehicle (RLV) is extremely significant and certainly required to be light-weight. Additionally, high thermal gradient in- duced by “aerodynamic heating” on different parts of aircrafts causes a large thermal stress, which would lead to a huge damage for hypersonic aircrafts. Therefore, the main function of the TPS is to keep the struc- tural temperature of vehicles within an acceptable range and also to provide an appropriate aerodynamic surface to avoid premature tran- sition to turbulence flow during the atmospheric re-entry [1]. Espe- cially, the leading edges and nose cone of hypersonic aircrafts require the most sophisticated TPSs, since they experience much larger thermal and structural loads [2]. In the previous investigations, efforts mainly focus on the study of passive TPSs for supersonic aircrafts. Fatemi and Lemmen [1] applied equivalent thermal and mechanical properties of a honeycomb core into a laminate shell structure, and showed the reasonably accurate thermo- mechanical behavior and considerably decreased the computational costs of the finite-element analysis. Based on the asymptotic expansion method, Buannic et al. [3] adopted the homogenization theory to compute the effective properties of corrugated core sandwich panels. Zhu et al. [4] made a comparison between the integrated sandwich structure with titanium foam core as insulation and a structural panel with Saffil insulation. It indicated that the integrated sandwich design tends to require thick insulation while the Saffil design is in favor of thin structure for temperature alone. Bapanapalli et al. [5] established a procedure for the optimization to design an integral thermal protection with a minimum mass, and simplified the geometry of the corrugated core sandwich panel and obtained a preliminary design. The improve- ments in design have been proposed as a portion of the future work to make the TPS to be lightweight. Bezazi et al. [6] described the prop- erties of mechanical in-plane and thermal conductivity for a novel cellular configuration, named hexagonal rectangular honeycomb for multi-functional applications. An integrated thermal protection system for spacecraft reentry (i.e., a corrugated core sandwich panel), which concurrently met the thermal and structural requirements, was opti- mized to the minimal mass by Gogu et al. [7]. Using one-dimensional analysis for transient and non-linear problems, Ferraiuolo and Manca [8] developed a procedure to estimate the temperature variation with time and space of a multi-layered body, which was subjected to aero- dynamic heating. A micromechanical method was developed by Martinez et al. [9] in https://doi.org/10.1016/j.ijthermalsci.2019.02.002 Received 23 March 2017; Received in revised form 6 March 2018; Accepted 2 February 2019 ∗ Corresponding author. School of Marine Science and Technology, Northwestern Polytechnical University, Box 24, Xi'an, 710072, China. E-mail address: xgn@nwpu.edu.cn (G. Xie). International Journal of Thermal Sciences 139 (2019) 118–128 1290-0729/ © 2019 Elsevier Masson SAS. All rights reserved. T