Additive Manufacturing of Embedded Strain Sensors in Structural Composites

In this paper, a multi-walled nanotube-based nanocomposite is developed for the 3D printing of embedded strain sensors in structural composites. The formulation of nanocomposites is investigated, and the optimal nanotube concentration is identified, considering multiple aspects including cost, processing capability, and printing capability. The developed nanocomposites are directly printed onto glass fiber fabrics using the material extrusion-based additive manufacturing method. Then, the 3D printed nanocomposites in the format of strain gauges are employed for the fabrication of continuous fiber-reinforced composites with embedded sensors. To demonstrate the load and strain sensing capability, composite laminate beam samples are fabricated for testing. The microstructures, potentially embedded voids, and nanoparticle distributions are characterized using a scanning electron microscope. Moreover, the load sensing functionality of the manufactured glass fiber composites using embedded nanocomposite strain gauge is characterized under 3-point bending load conditions. The sensitivity, repeatability, and reliability of the 3D printed nanocomposites are experimentally characterized using a standard mechanical testing system. Particularly, the effects of maximum load and load rates on sensitivities of the developed composites are tested. The 3D printed strain gauges can be used for the monitoring of composite integrity, indicating their safety and reliability under complex and fatigue loading conditions.