OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Hypersonics The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: The objective of this research is to design hypersonic components and systems using mesostructures to improve manufacturability, maneuverability, speed, and range DESCRIPTION: With emerging manufacturing technologies, engineering design is no longer limited by traditional component manufacturing processes and intrinsic material properties that arise from crystal microstructures. Rather, complex small structures, i.e., mesostructures, may be produced by additive manufacturing (AM) to reduce weight by up to 90% (Deng), integrate components and functionality, and tune effective material properties. A variety of mesostructures have been created using AM technologies including truss structures, triply periodic minimal surfaces (TPMS), and honeycomb structures. With mesostructures, engineers can tune material properties, essentially creating new materials, metamaterials or engineered materials. The properties of the engineered materials with mesostructures can be described at the macroscale using effective material properties and can vary by orders of magnitude from the base material's properties. Therefore, mesostructures are revolutionizing engineering design and are particularly suitable for weight critical industries including hypersonics. In addition to the weight reduction due to the partial density, system weight is also decreased by component integration, multifunctional materials, and property and topology optimization with mesostructures. Engineered materials and AM technology with mesostructures simultaneously improve munitions readiness and effectiveness. There are many complex challenges in the characterizion and subsequent modeling of mesostructures. Many of the simplifying assumptions used to model the behavior of fully dense materials including isotropy, symmetry, and linearity are no longer valid for materials engineered with mesostructures. For example, most polycrystalline materials are isotropic, meaning they behave the same way in every direction. In contrast, most mesostructures are highly anisotropic. Effective material properties vary by orders of magnitude with rotation of the mesostructure. This anisotropy could result in catastrophic failures if not described in the analysis using advanced material models with tensor properties. Anisotropy is incredibly useful to optimize designs and tune material properties utilizing these advanced material models and tensor properties. For example, layered insulation with anisotropic thermal conductivity allows heat to flow from the leading edge along the outer lamina of hypersonic aeroshells while protecting the internal cavity and underlying sensitive components. Current engineering design and analysis techniques, tools, and software were not developed for multifunctional components and systems with variable, tensor material property fields enabled by mesostructures. In state-of-the-art design and finite element analysis (FEA), intrinsic material properties are assigned to entire components, boundary conditions are applied, the analysis is executed, and the thermomechanical response is output. Often entire systems are reinforced, redesigned, or even rejected because the FEA reveals a point failure at a load concentration. The tools required to navigate the burgeoning design space with mesostructures and advanced composites are in development. To inform this development, we must explore the design space, understand the tradeoffs, identify multi-objective optimization functions, develop advanced material models with effective tensor properties, and ultimately map the mesostructures to the hypersonic systems. Therefore, the current challenge in AFRL/RW is to apply mesostructures to a variety of novel hypersonic designs to improve manufacturability and performance in a parallel approach. Exploration of the design space requires the evaluation of the system for opportunities to integrate functionality, reduce component interfaces, distribute loads, reduce weight, and/or otherwise improve system level designs with the application of mesostructures. In the design process, many different variables should be considered for the trade study including but not limited to: anisotropic and multi-physics effective material properties, various base materials and material combinations, mesostructure refinement and density, manufacturability, deformation and distortion of mesostructures, and various types of mesostructures and transition structures. Finally, mesostructures will be mapped to the hypersonic system using advanced models to create fields of tensor material properties for improved manufacturability or performance of representative hypersonic systems. Effective material properties of particular interest include: stiffness, fracture toughness, thermal conductivity, specific heat, density, impact resistance, surface roughness, maximum service temperature, creep, and strength. Manufacturability of mesostructures continues to challenge the AM community. If the engineered materials are not currently manufacturable, manufacturing limitations and progress will be explored in-depth. If the engineered materials are manufacturable, the materials will be characterized to understand the tensor properties, validate advanced material models, and demonstrate mapping, deformed and transition structures, the variable property fields. PHASE I: During phase I, awardees will select a commercial or government-of-the-shelf (GOTS) FEA solver for implementation. Extensive literature surveys and prior research highlighting the advantages and limitations of the chosen approach is required. The firm will then select a representative hypersonic system, subsystem, or geometry for redesign with mesostructures. The objective performance and/or manufacturing improvements and trade space will be defined. The technical approach including design optimization scheme, advanced material models, and mapping functions will be identified. Effective tensor properties for the materials engineered with mesostructures will be collected from the literature and supplemented with FEA analysis, as required. Manufacturing limitations and progress will be identified PHASE II: During phase II, the hypersonic system, subsystem, or geometry redesigned with mesostructures will be completed, modeled using the FEA solver selected in Phase I, and analyzed to demonstrate through modeling and simulation the improved maneuverability, speed, and/or manufacture. Mesostructures and engineered materials will be manufactured and characterized to validate advanced material models and demonstrate tunable tensor properties. Documentation of the implementation including user manuals, theory manuals, validation cases, examples, and source code with U.S. government data rights is required. PHASE III DUAL USE APPLICATIONS: Following successful and innovative applications of mesostructures into hypersonic systems and design, analysis, and optimization tools within Phase I and II, Phase III funding will be available from 6.2 funding for the Advanced Manufacturing Enabled Technologies for Aerodynamics (Advanced META). The contract vehicle is currently being explored with the transition partner, Boeing BRD&T, for integration into developmental hypersonic, high-speed and weight critical systems using the developmental tools. REFERENCES: 1. Deng, Biwei. Lightweight Mechanical Metamaterials Based on Hollow Lattices and Triply Periodic Minimal Surfaces. 2019. 2. Purdue University, PhD Dissertation; Yang, Lei. Continuous Graded Gyroid Cellular Structures Fabricated by Selective Laser Melting: Design, Manufacturing and Mechanical Properties. Materials and Design. 162, 2019, p. 394-404; KEYWORDS: Mesostructures; Metamaterial; Hypersonic; Design Optimization; Maneuverability; Engineered Materials
