Refractory Metal Foam Core Sandwich Panel Development to Enable Morphing of Hypersonic Air Platform Control Surfaces, Phase II

Development of surface morphing technology is critical to enhance performance of multi-mission air platform aerodynamic control surface components operating under high-Mach conditions. In Phase I, Ultramet demonstrated the initial feasibility of a robust flexible, oxidation-resistant, and highly insulating multilayered structure for deformable aerodynamic control surfaces. In conjunction with design and modeling performed by Plus Designs Inc., the feasibility of a nominally 1" thick multilayered panel composed of thin refractory metal front side and back side facesheets, highly porous refractory metal structural open-cell foam, and ceramic felt insulation was demonstrated. Based on thermostructural modeling, front side (hot face) facesheet materials were selected that have good potential to operate at 3000°F and remain elastic. The flexible, high temperature open-cell foam near the hot face serves as a thermal/chemical standoff between the front side facesheet and oxide felt insulation to prevent unwanted reaction and reduce heat transfer to the felt. Near the back side (cool face), the foam provides additional structural support and interface contact resistance to reduce heat transport. During oxyacetylene torch testing to 3000°F, heat transfer through the multilayered structure yielded a back face temperature that was close to the 300°F target, and a means of further reducing temperature below the target was established through modeling of different insulator material combinations. Room temperature flexural tests to a 12" radius of curvature showed the ability of the multilayered structure to deform elastically, and thermostructural modeling indicated good potential for the structure to behave similarly at 3000"F. Maintaining high temperature oxidation resistance for a morphing surface is a significant challenge, as conventional ceramic protective coatings are brittle. The feasibility of thin, high-ductility platinum group metal coatings diffusion-bonded to the front side facesheet materials was demonstrated through oxyacetylene torch testing up to 3000°F to show oxidation resistance, and through post-test cyclic room temperature flexural testing to show retention of coating/facesheet flexibility and damage resistance. In Phase II, Ultramet will team with Northrop Grumman Defense Systems, a potential end user of the technology, and Plus Designs to target a specific MDA program application for the surface morphing technology and demonstrate performance through panel screening tests at the Air Force LHMEL facility to compare performance with competitive designs and through increased-scale panel tests at the Air Force Aerospace Structures Test Complex, which will include cyclic panel bending during high temperature testing. The deformable surface technology is anticipated to find application in non-airbreathing as well as airbreathing vehicles, and the proposed Phase II development and testing will be beneficial for both. Approved for Public Release | 22-MDA-11102 (22 Mar 22)