Piezoresistive polymer nanocomposite sensors for structural health monitoring of concrete beams

Various methods such as fiber optic sensors, acoustic emission techniques, digital image correlation, embedded sensors, and strain gauges are utilized to monitor stress/strain in concrete. The embedded sensors offer advantages of real-time monitoring, high accuracy and sensitivity, and long-term performance data. These sensors can be embedded in concrete to monitor the condition of a section of the concrete at critical points throughout its life cycle. This work presents an innovative approach using a 3D-printed piezoresistive sensor composed of a conductive thermoplastic polyurethane filament to monitor strain within a concrete sample under four-point loading conditions. The performance of the sensor at different locations, temperature and humidity within the concrete was studied. The findings demonstrate that the 3D-printed sensor effectively captures strain within concrete samples under cyclic loading. The sensor’s signal output varies between 20% and 120% based on its distance from the crack location, enabling accurate crack position monitoring. Additionally, the sensor’s response depends on temperature and humidity, and prior to failure it closely follows a mathematical model based on beam theory, achieving an R2 value greater than 0.94. Furthermore, artificial intelligence-based clustering achieves 98.9% accuracy in identifying crack locations from sensor data, highlighting its potential as a practical tool for structural health monitoring. The results suggest that when the sensor is positioned close to a theoretical crack formation location, a high-confidence signal is obtained.