Development of High-Sensitivity and Low-Cost Electroluminescent Strain Sensor for Structural Health Monitoring

Visualized strain/stress sensing is receiving interests in structural health monitoring area, but former approaches cannot be effectively applied to civil infrastructure monitoring, because of limited sensitivity to low-level response and/or limited response to civil structures for both static and dynamic strain/stress. This paper presents a high-sensitivity and low-cost method to visualize the strain by employing the precisely controllable Wheatstone bridge and monochrome electroluminance (EL) technology. A sensor prototype is developed to convert the structural strain responses into visible brightness change with brightness change mode (BCM) and to color change with color alternation mode (CAM). In the BCM, the brightness can be changed according to the strain change. In the CAM, two different-color EL panels are used to light on to indicate the necessity for the professional structural health evaluation. Brightness linearity evaluation results show that the BCM is suitable for both static and dynamic low-level strain visualization. Bill of materials shows the cost of the prototype is as low as U.S. $46 including the EL panels.