Using Additive Manufacturing to Improve Supersonic Air Vehicle Design

Researchers at ARI are studying using additively manufactured materials to improve the design and performance of support structures within super- and hypersonic air vehicles.

Aerospace structural sizing and design for supersonic/hypersonic air vehicles involve complicated reaction forces between the hot outer surfaces and the cooler inner surfaces of the vehicle as they strive to reach a state of strain equilibrium. The skin panels of such air vehicles (Fig. 1) are known to further complicate design due to the coupled thermal, mechanical, and aerodynamic loads leading to nonlinear panel responses and potential aero-elastic instability. These panels are stiffened to combat these responses by adding hat stiffeners/honeycomb or by making the panel thicker; however, a stiffer skin necessitates stiffer internal structures, adding weight to the vehicle. An alternative approach is the design of monocoque, or structural skin, panels with tailored compliance to passively control buckling, snap-through, internal resonances, and/or aero-elastic instabilities. The use of metallic additive manufacturing (AM) in this project significantly opens the design space for such panels allowing for novel structural designs impossible to manufacture using traditional machining techniques.

Figure 1: Schematic of notational hypersonic air vehicle with panel motivating design constraints.

Utilizing additive manufacturing techniques to build structural members such as beams and/or panels is still in its infancy; therefore, tunning of the AM process as it applies to panels and/or structural members is needed. Utilizing the currently available AM machine at ARI, small scale panels (Fig. 2) are being printed and tested to determine optimum build parameters and support structures to produce repeatable panels. A plot of the 3D shape of the panel as printed is shown in Fig. 2b demonstrating stable geometry after printing. An annealing procedure will be performed before removal from the build plate to preserve the final geometry of the panel. Further study into support placement, build orientation, and annealing processes for AM structures will be pursued with the final goal to maintain geometric errors within the same order of magnitude of machined panels when considering simple flat geometries.