Thermo-Mechanical Performance Of Micro-Truss Sandwiched Panel With Flow Channels Made By 3D Printing

Hypersonic vehicles have to withstand extremely high aerodynamic heating and pressure loads in their service environment. What's more, multifunction and lightweight are needed for the aerospace structure design. Therefore, it is particularly important to investigate the integrated thermal protection system (ITPS) which possesses multifunction of thermal protection and load-bearing capabilities. In recent years, domestic and overseas scholars put forward many schemes. Among them, lattice truss sandwiched panel is the best choice for multifunctional structures because of its extraordinary mechanical performance. However, traditional processing technology limits the application of lattice truss structures. In this thesis, based on Additive Manufacturing(AM) and the design concept of lightweight and multifunction, multi-layered truss sandwiched panel and a new micro-truss sandwiched panel with flow channels are manufactured. The mechanical performance of multi-layered truss structures and thermo-mechanical performance of a new micro-truss sandwiched panel with flow channels are analyzed by experiments and numerical simulation. The main contents are as follows:(1) Mechanical performance of the multi-layered truss structures fabricated by 3D printing. Traditional approaches not only are difficult to manufacture complicated structures but also produce many defects. In this thesis, a simple 3D printer is used to fabricate multi-layered truss structures by FDM technology, and specimens are tested in quasi-static compression to assess their mechanical properties. The results show that it is convenient and successful for AM to fabricate complicated structures which can not be achieved by traditional technology. Compared to other lattice structures, multi-layered truss structures exhibit excellent mechanical properties. Besides, finite element models with displacement loading and periodic boundary conditions are simulated to assess the compressive elastic modulus and the value is a little higher than experiment result.(2) Thermal performance of a new micro-truss sandwiched panel with flow channels. Good performance and lightweight are urgently needed for aerospace structures. Therefore, it is of great significance to carry out the research on integrated thermal protection system (ITPS) which can meet the requirements of thermal protection and load-bearing. For aircraft structure design requirements, a new micro-truss sandwiched panel with flow channels is proposed. The triangular flow channels are directly connected with heating surface, other space between two face sheets is filled with the stretch-dominated micro-truss architecture. As an actively cooled UPS, the new structure can be used in moderate heat fluxes and long times thermal environment. For the thermal performance evaluation, the complicated heat transfer mechanism in structure is analyzed in details. Based on some conservative assumptions, the analytical model and evaluation method about channel heat transfer are given under three typical boundary conditions. A special example illustrates the effectivity and validity of the analytical solution by comparing to detailed results provided by Fluent software.(3) Mechanical performance of a new micro-truss sandwiched panel with flow channels. Considering that the mechanical performance of the new configuration also has an important influence on structure application. The complicated sandwiched panel is homogenized as a continuous, orthotropic plate to estimate its mechanical characteristics. A new implementation approach of the asymptotic homogenization method is used to determine the equivalent stiffness properties by analyzing model in ANSYS software. This equivalent method is easy and convenient to manipulate and of high efficiency. The new structure with triangular flow channels has better performance than that with elliptical flow channels, and various stem diameters as well as angles have a little influence on the stiffness properties. Besides, quasi-static compressions about different kinds of the new sandwiched panel are tested to compare mechanical properties. Results indicate that the new micro-truss sandwiched panel with flow channels has the same high mechanical performance as well.