Review on strain transfer effects based on material properties for flexible sensors in structural health monitoring

Abstract Sensor accuracy is vital for effective structural health monitoring (SHM). However, due to the shear lag effect, the strain transferred from the structure to the sensor experiences some loss, which affects accuracy. This paper offers a review of strain transfer effects for flexible sensors within SHM, highlighting the vital role that sensors play in accurately detecting structural strain. A thorough understanding of strain transfer characteristics is crucial for improving measurement accuracy, especially in complex and often harsh conditions typical of practical applications. This review delves into the interactions between substrates and nanomaterials, placing particular emphasis on interfacial mechanics and the influence of various loading conditions, including temperature fluctuations, cyclic loads, boundary conditions, and diverse damage modes, on the strain transfer efficiency. We also discuss the unique properties of flexible sensors, such as their nonlinear responses and increased sensitivity to environmental factors, which further complicate strain measurement. By systematically analyzing these strain-transfer mechanisms, this study aims to establish a robust theoretical framework that supports the development and optimization of flexible sensors for SHM applications. The insights gained from this review are intended to enhance the reliability and accuracy of flexible sensor-based strain measurements, ultimately improving the effectiveness of health monitoring and condition assessment of critical infrastructure.