Embedding optical fiber strain sensors in aerospace aluminum alloys for structural health monitoring is an important constituent capability for the Virtual Digital Fleet Leader or Digital Twin. In the 2015 NASA Technology Roadmap, TA-12: Materials, Structures, Mechanical Systems, and Manufacturing, the Digital Twin technology state of the art is described as TRL 1. The Digital Twin is in the concept stage, but the constituent capabilities are in various stages of development. The technology performance goal is described as TRL 6. This would include the ability to adjust life prediction based upon the monitored past, the current structural status, and the potential new environments coming in the vehicle life, with confidence in sensor interpretation, and in integrated prediction accuracy. We plan to elevate embedding optical fiber strain sensors in aerospace aluminum alloys to TRL 6 by the end of the Phase II program, fully addressing the need for this constituent capability. NASA plans to have the Digital Twin capability ready for Planetary Exploration Design Reference Missions to Mars in 2033, with the technology ready by 2027. We are on track to meet these goals.
This program, which embeds optical fiber strain sensors anywhere in a metal part, provides multifunction aluminum parts with integrated health monitoring sensors in support of the Digital Twin program. The Digital Twin program is, in fact, a joint Air Force - NASA effort. The initial commercial applications of this technology lie clearly with defense and aerospace manufacturers. Aerospace and Defense are early adopters of additive manufacturing because it enables lightweight designs and the production of parts with complex geometries. Additionally, aerospace and defense manufacturers frequently incorporate high value materials, and additive manufacturing allows them to maintain fine control of material properties and reduce raw material waste. There are very few conceptual approaches for fabricating metallic load-bearing structure with embedded multi-functional capability. Traditional fusion based welding and/or thermomechanical processes used for fabricating metallic structure would destroy delicate instruments. The solid-state nature of UAM is unique in that it allows sensitive sensors, such as thermocouples and strain gages, to be placed inside of metallic structure.