Tech Update


Fabrisonic's Embedded-in-AM Capability Key to NASA Project

Wednesday, December 18, 2019

Recently Fabrisonic LLC partnered with Luna Innovations on a project for NASA to gather data in cryogenic fuel pipes for rocket test stands at NASA Stennis Space Center. NASA’s goal was to get data on pressure and temperature gradients inside of their fuel piping closer to the test article to better understand how a particular engine is behaving.

Why the partnership? The solid-state nature of Fabrisonic’s Ultrasonic Additive Manufacturing bond allows for encapsulation of wires, fibers, and sensors into a metallic substrate. Over the years, Fabrisonic has embedded strain gauges, microphones, thermocouples and ultrasonic inspection sensors into solid metal parts. By burying a sensor into solid metal, according to Fabrisonic officials, the sensor is hardened, allowing it to operate in more aggressive environments; located exactly where the relevant data is needed; and is constrained by metal instead of adhesives, which allows for a much larger operating regime.

Historically, NASA has mounted sensors to the outside of the pipe using elbows and ports, which communicates some data. However, it does not provide the same fidelity as a sensor located adjacent to the fuel stream, and can disrupt the fuel stream. Similarly, NASA has mounted sensors directly into the flow path using pass-throughs in the existing pipe. These ports and pass-throughs can influence the fuel flow, adding uncertainty to the measurements.

The Fabrisonic team assigned to this project 3D printed sensors directly into the wall of the pipe. This allows a suite of sensors to be embedded in essentially the same space, reportedly providing a much clearer picture of thermal and pressure gradients in the piping, as no ports are required. Luna Innovations provided the fiberoptic-based sensors, chosen due to their small size. In addition, the fiber-based sensors also collect data over the entire length of the fiber, allowing for a continuous length of sensing instead of a fixed point.

The Fabrisonic team printed only a portion of the pipe to save on printing expense and to prove out the concept. The team started with an existing pipe, milling a flat section into its OD to create a landing strip for embedding, then cutting a small groove to positively locate each fiber. Once the fibers were inserted by hand, Fabrisonic printed additional material over the landing strip to build the OD back to spec. After printing, CNC milling removed extra printed material.

The team has tested the pipe at various pressures and temperatures to calibrate the sensor. This included boiling the pipe in water and filling it with liquid nitrogen to emulate cryogenic fuel. The pipe reportedly continued to provide solid data throughout all of the extreme conditions. The project’s next phase: Print a larger pipe section for use at NASA Stennis Space Center.


See also: Fabrisonic LLC

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