Embedded Piezoresistive Sensors Printed by FFF for Aerospace Applications

Fused filament fabrication (FFF) is a promising fabrication method to print novel piezoresistive sensors with capability of self-sensing for advanced applications. Moreover, considering to its direct integration into structural parts, it contributes to the fabricate more sensitive strain-sensors without installation problems. However, very few of studies focused on high strength piezoresistive strain sensors suitable for structural parts. In this study, the aim is is to print embedded piezoresistive sensors using multi-material extrusion system in a single-step producing cycle for advanced engineering applications. The sensors were fabricated with 1 and 3 wt.% carbon nanotubes (CNT) reinforced polyetherimide (PEI) filaments using twin-screw extruder. Sensor substrate and conductive traces are printing via multi-nozzle FFF printer using neat PEI and CNT reinforced PEI filaments and two different strain gauge pattern with two different CNT concentration were studied. Electrical conductivity measurements were performed to CNT/PEI filaments and surface conductivity of the 3 wt.% CNT/PEI nanocomposite filaments was found 5.93 x 10-2 S/cm. Then, cyclic tensile tests were conducted coupled with in situ electrical measurements. Strain sensors with 3 wt.% CNT/PEI exhibit excellent piezoresistive behavior and reliable sensor response during cyclic tensile tests.