An embeddable wireless strain sensor based on inductive coupling

Abstract

This paper reports the development of low-cost inductively coupled passive wireless strain sensors which could be easily embedded within composite prepreg layers for structural health monitoring application. Sensors of different patterns were fabricated and were experimentally tested. Theoretical modeling utilizing three different approaches and electromagnetic simulation were performed to estimate both the strain-free resonant frequency and the shift of resonant frequency of the sensor due to strain. Both the modeling and simulation results showed satisfactory agreement with the experimental data. Experimentally, all the sensors showed great strain sensing potential, as good linearity between resonant frequency and strain and relatively low hysteresis characteristics were observed. In addition, several possible influences on sensor performance were investigated, including the misalignment between sensor and antenna in terms of relative angle, relative in-plane position and relative out-of-plane position, and the effect of metal plate in the vicinity of the sensor. Additionally, the feasibility of constructing sensor array was verified. Finally, no significant degradation of interlaminar shear strength of the composite material was observed due to sensor embedment.