The Department of Defense, specifically the Navy, is seeking proposals for the Small Business Innovation Research (SBIR) program focused on developing a Highly Applicable Mechanical Metamaterial (HAMM) for high G-load flight structures. The objective is to create a mechanical metamaterial with an adaptive hierarchical microarchitecture that can withstand extreme mechanical loading and high temperatures, utilizing novel high entropy alloys to enhance specific strength while minimizing material usage. This initiative is crucial for advancing flight vehicle structures operating in hypersonic environments, where traditional materials face limitations due to stringent temperature and mechanical load requirements. Interested parties should note that the solicitation is set to open on January 8, 2025, with proposals due by February 5, 2025, and can find more information at the official SBIR website.

## Description

Flight vehicle structures operating in hypersonic environments are traveling at speeds above MACH 5 and may experience structural G-force loads above 50Gs. These variables make the material property requirements very stringent for survivability. To account for these conditions, structural alloys designed must have high strength, creep resistance, and high operating temperature. Historically, new material systems have always played a transformative role in advancing these capabilities. In the operation of flight structures, reducing weight while increasing strength improves flight performance with each new design iteration. For structural materials, aluminum and titanium alloy manufacturing have made advances by providing structures with high specific strength in operation. These alloys are used in a limited number of flight applications for hypersonics, due to operational temperatures of ~300&deg;C (Al alloys) and ~540&deg;C (Ti alloys). Nickel based alloys, like Inconel, provide a solution when extreme temperatures, mechanical loads, and high corrosive environments are persistently present. Inconel has been able to withstand temperatures up to 1200&deg;C, which makes it very unique for these environments. The caveat is that traditional manufacturing makes Inconel production expensive due to machining and overall material cost. For sustainability, Inconels have a material design limitation due to the requirements for a high nickel concentration, &gt; 50%. Advanced manufacturing methods that use less material, reduce machining time, or provide a whole new materials solution without significant loss of mechanical properties are of need. Mechanical metamaterial provide a unique approach by specifically using advanced manufacturing to create hierarchal lattice structures. These structures have macroscopically high mechanical strength in the designed principle direction due to their multiple instances of material orthotropy. Topological optimization has been utilized to research hierarchal structures that are specifically designed for higher loads. These designs seek to use less material without sacrificing mechanical capability. This SBIR topic looks for a Mechanical Metamaterial structural design that is able to maintain or improve upon the properties of a forged structural component. This topic intends for the use of new high entropy alloys that reduce or provide alternatives to nickel based alloys. The design should be informed by using modern topological optimization tools driven by machine learning. The final design will be a representative component structure to be tested under loading conditions experienced by hypersonic flight environments.Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. owned and operated with no foreign influence as defined by 32 U.S.C. &sect; 2004.20 et seq., National Industrial Security Program Executive Agent and Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence and Security Agency (DCSA) formerly Defense Security Service (DSS). The selected contractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances. This will allow contractor personnel to perform on advanced phases of this project as set forth by DCSA and SSP in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material during the advanced phases of this contract IAW the National Industrial Security Program Operating Manual (NISPOM), which can be found at Title 32, Part 2004.20 of the Code of Federal Regulations.

## Objective

Develop a mechanical metamaterial with adaptive hierarchical periodic microarchitecture that can survive increased mechanical loading at high temperatures. The design will provide an increase in overall specific strength using novel high entropy alloys per volumetric performance.

## Phase I

Develop a high entropy alloy and architecture with an optimized design for incorporating high mechanical loads via advanced manufacturing. Produce sample test articles using advanced processing and characterize them under tension, compression, and hardness. Assess the alloy through crystallography, microscopy, calorimetry, and gravimetric analysis to access ablative mass loss at high temperature. The resulting article must have a low oxygen concentration and be able to operate in extreme temperatures above 1000&deg;C. Use an understanding of characteristics to demonstrate a viable proof of concept.

## Phase II

Create a larger mechanical test architectures to conduct a side-by-side comparison of properties to other comparable structural alloys. Perform a manufacturing repeatability analysis on the manufacturing process for this optimized mechanical metamaterial. Establish a manufacturing process workflow to incorporate an optimization design of experiments to allow for future concept variability.It is probable that the work under this effort will be classified under Phase II (see Description section for details).

## Phase III: Dual Use Applications

Integrate manufactured metamaterial into a component scale flight experiment and begin developing a pilot line for transition to full production. Support the government in transitioning the technology for government use. The transitioned product is expected to be able to support current and future weapon and space systems, as well as a wide range of other air, land, and sea-based systems.Commercial applications should be considered for transition (i.e., 5G, navigation systems, and tracking systems). The primary objective of this project is for transition to defense contractors for high-speed weapons and space systems. To meet these needs, maturation and packaging of the technology to meet practical size, weight, and power constraints will be required. Extreme environments may require special considerations to conform to airframe shape and shielding from the aerothermal environment.

Highly Applicable Mechanical Metamaterial (HAMM) for High G-Load Flight Structures.

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