Integrated impedance and Lamb wave–based structural health monitoring strategy for long-term cycle-loaded composite structure

Impedance of a sensor is sensitivity to small structural damage which surrounds the sensor. Lamb wave propagation provides higher damage detection efficiency in the range of large area. Both methods have been widely developed for structural health monitoring. This article presents integrated impedance and Lamb wave–based structural health monitoring strategy for composite pressure vessels. The output of the presented structural health monitoring strategy includes distribution and classification of damage and health condition of sensor network under varying internal pressure loading environments. In the strategy, a novel damage index adjusting method for Lamb wave damage detection is developed based on the signal features of real and imaginary parts of the sensor impedance. First, the potential structural damage is pre-warned by monitoring the impedance variation of the piezoelectric transducer sensor network. Then, the health condition of sensor network under the working condition is assessed by impedance-based self-diagnosis method; subsequently, the Lamb wave damage index is adjusted based on the result of sensor self-diagnosis. Finally, on the basis of sensor self-diagnosis and damage index adjustment result, damage identification and classification are performed. Practical efficacy of the structural health monitoring approach is tested by the damage monitoring experiment on loaded composite structure.