Design approximation and proof test methods for a cellular material structure

The Mission Adaptive Digital Composite Aerostructure Technology (MADCAT) project is to assess the feasibility of ultralight lattice structures for high performance space and aero applications, using building block based construction methods, and with primary potential benefits of system mass reduction over the duration of mission life cycles that can span both space and aero operation modes. As part of the project, an ultralight technology demonstrator was designed, built, and tested, with aerodynamic and structural mechanical overviews provided in prior work [1] [2]. This article details the first order design approximation method estimation used to set a preliminary design envelope and the corresponding proof load testing method for the final MADCAT demonstrator, as a notional optimized structural element with variable cross section. For the proof load testing, a complete built model was load tested under estimated critical loading conditions, with loads applied using a whiffletree system. Architected cellular materials represent a new frontier in material science, with potentially revolutionary benefits such as high specific stiffness in the ultralight density regime (<10 kg/m3). However, because most of these materials are made using additive manufacturing, they are limited in scale (<1m) due to size constraints of the 3D printing platform. A new approach is based on the reversible assembly of discrete lattice building blocks. This method has been employed to design and build a large scale (>1m) ultralight lattice structure with application as novel aircraft as part of the Mission Adaptive Digital Composite Aerostructure Technology (MADCAT) project. Prior to wind tunnel testing, the structure had to undergo non-destructive, full-scale tests to validate modeling predictions and ensure factors of safety. This paper will describe the required first order design approximation method estimation to set a preliminary design envelope and a corresponding proof load testing method for the final MADCAT demonstrator, as a notional optimized structural element with variable cross section. For the proof load testing, a complete built model was load tested underestimated critical loading conditions, with loads applied using a whiffletree system. This work presents the testing and validation of the largest ultralight lattice material structure built (2m in length), which represents a significant step towards full-scale integration of architected cellular materials into high performance space and aero applications.