Sensitivity increase of 3D printed, self-sensing, carbon fibers structures with conductive filament matrix due to flexural loading

TL;DR

This paper explores how 3D printed, self-sensing carbon fiber structures can have their sensitivity enhanced through a breaking-in process involving large compressive loads, improving their sensing capabilities.

Contribution

It introduces a novel method of increasing the sensitivity of 3D printed carbon fiber strain gauges via a breaking-in process and demonstrates the benefits of conductive filament coextrusion for sensor reliability.

Findings

Sensitivity increases irreversibly after breaking-in

Local fiber failure enhances gauge factor

Coextrusion improves electrical contact and noise performance

Abstract

The excellent structural and piezoresistive properties of continuous carbon fiber make it suitable for both structural and sensing applications. This work studies the use of 3D printed, continuous carbon fiber reinforced beams as self-sensing structures. It is demonstrated how the sensitivity of these carbon fiber strain gauges can be increased irreversibly by means of a pretreatment by ``breaking-in'' the sensors with a large compressive bending load. The increase in the gauge factor is attributed to local progressive fiber failure, due to the combination of the thermal residual stress from the printing process and external loading. The coextrusion of conductive filament around the carbon fibers is demonstrated as a means of improving the reliability, noise and electrical connection of the sensors. A micrograph of the sensor cross section shows that the conductive filament contacts the various carbon fiber bundles. All-in-all, the use of ``breaking-in'' carbon fiber strain gauges in combination with coextrusion of conductive filament hold promises for 3D printed structural sensors with a high sensitivity.