Swansea University researchers have used Optomec aerosol jet technology and successfully printed strain and optical creep sensors onto the surface of jet engine blades.
Aircraft maintenance is an expensive, time-consuming process. The aerosol jet technology enables printing sensors directly onto aerospace components which could optimize the process considerably. The team used a laser inspection system and optical light measurement on the sensors and determined the blades’ degree of creep to less than 10 nanometers.
The researchers at Welsh Center for Printing and Coating (WCPC) at Swansea University said that the new technology can be used to monitor the blades in real time, which could result in increased fuel efficiency and higher running temperatures.
The printing process begins by using a mist generator that atomizes a conductive nano-silver ink. The conductive nanoparticles are further refined in a virtual impactor. The resultant material is aerodynamically focused with a flow guidance deposition head, creating an annular flow of sheath gas which collimates the aerosol.
The coaxial flow exits from the flow guidance head through a nozzle which is directed at the substrate. This coaxial flow focuses the material stream to one-tenth the size of the nozzle orifice. Material patterning is done using CNC commands which positions the flow guidance head while the substrate remains intact.
A five millimeter standoff distance between the substrate and the deposition head ensures that the material gets deposited accurately on non-planar substrates into channels and existing structures.
A thermal post-treatment imbues the sensors with the right mechanical and conductive properties and ensures adhesion to the substrate. The research team also investigated possibilities of locally pressing the deposition with a laser treatment process allowing the use of materials with low temperature tolerances. This resulted in a high-quality film as small as 10 nanometers with very good edge definition and near-bulk properties.
Nano-silver ink remains stable up to 250 degrees Celsius however researchers are developing nano-platinum ink which can withstand temperatures of up to 1200 degree Celsius. The advancements will help the aerospace industry to overcome the temperature limitations.
The compressor blades of jet engines are subject to lower temperatures than the high-pressure and low-pressure turbines. The sensors could most likely be used on those components. Although the sensors enable monitoring stress and degree of creep in real time, they would add tremendous value to high-pressure turbine blades where stress are creep are significantly higher.
Excerpts from Engineering.com. Image courtesy of WCPC