Damage detection for structural health monitoring using ultra-sensitive flexible piezoelectret sensors

Damage detection is of great importance for structural construction management and safety. In this study, an ultra-sensitive flexible piezoelectret sensor for damage monitoring in structural health monitoring (SHM) is designed and fabricated, based on excellent electromechanical properties and piezoelectric response characteristics of electret films. The charge stability of the piezoelectret sensor was demonstrated by continuous potential measurement experiments. The experimentally measured piezoelectret coefficient is 6610 pC/N, which is about 10 times that of ordinary piezoelectric ceramics and proves the high sensitivity of piezoelectret. A series of comparative experiments on the piezoelectret sensor and piezoelectric ceramics demonstrate the high performance of the former. According to the damage detection test results, the damage index of cement mortar specimens was obtained. The linear relationship between the damage index and the crack widths proves the excellent performance of the piezoelectret sensor. A piezoelectret array is also used to detect cracks in cement mortar specimens, and can roughly estimate the depth of the fracture based on the damage index (DI) value of the sensing array.