Integrated Wireless Distributed Strain Sensing Using Flexible Electronics for Structural Health Monitoring

Real-time, distributed monitoring of the structural integrity of active space habitats is a critical function for manned-space missions, requiring systems that are redundant, compact, robust, and easily reproducible. Toward this goal, we developed resistive and capacitive strain gauges (CSGs) using commercial flexible printed circuit (FPC) technology that are directly integrated with readout electronics for distributed and wireless structural health monitoring. In our prototype system, we distributed 16 gauges that are interconnected on a structural Kevlar strap. Using a single flat flexible cable (FFC) cable between each device, the gauges are daisy-chained to a control hub, where strain information is wirelessly relayed from the hub to a base station via Bluetooth. The developed capacitive and resistive gauges were tested for dynamic strain while attached to Kevlar straps that have a maximum loading of 26.7 kN. We measured gauge factors (GFs) of 1.70 and 1.55 for capacitive and resistive gauges, respectively. The readout system has a volume of 0.1976 cm³ and is capable of interconnecting up to 16 gauges per hub, and multiple hubs can be connected to a base station for large-area strain monitoring.