Adaptive Thermal Conductivity Metamaterials: Enabling Active and Passive Thermal Control

The novel adaptive thermal metamaterial developed in this paper provides a unique thermal management capability that can address the needs of future spacecraft. While advances in metamaterials have provided the ability to generate materials with a broad range of material properties, relatively little advancement has been made in the development of adaptive metamaterials. This metamaterial concept enables the development of materials with a highly nonlinear thermal conductivity as a function of temperature. Through enabling active or passive control of the metamaterials bulk effective thermal conductivity, this metamaterial that can improve the spacecraft's thermal management systems performance. This variable thermal conductivity is achieved through induced contact that results in changes in the F path length and the conductive path area. The contact can be generated internally using thermal strain from shape memory alloys, bimetal springs, and mismatches in coefficient of thermal expansion (CTE) or it can be generated externally using applied mechanical loading. The metamaterial can actively control the temperature of an interface by dynamically changing the bulk thermal conductivity controlling the instantaneous heat flux through the metamaterial. The design of thermal stability regions (regions of constant thermal conductivity versus temperature) into the nonlinear thermal conductivity as a function of temperature can provide passive thermal control. While this concept can be used in a wide range of applications, this paper focuses on the development of a metamaterial that achieves highly nonlinear thermal conductivity as a function of temperature to enable passive thermal control of spacecraft systems on orbit.