Cement-based piezoelectric composite sensor designed for charactering the three-dimensional stress state in concrete

We reported a sensor, designed based on the specific working modes of piezoelectric, to characterize the three-dimensional (3-D) stress state in concrete. The sensor contains 6 piezoelectric elements: 3 elements working in normal mode to measure the normal stress, and 3 elements working in shear mode to measure the shear stress. Cement-based piezoelectric composite, fabricated by cutting-filling method, was used to fabricate the sensor, as it has better mechanical compatibility with concrete than piezoelectric ceramics. By embedding the sensor into a cement mortar column, we systematically characterized its performance under dynamic uniaxial load from 3.0 MPa to 7.5 MPa with frequency from 1 Hz to 20 Hz. Results demonstrate that the sensor can measure the 3-D stress state in concrete well, and has good linearity, high sensitively, and excellent working bandwidth. The cross sensitivities of the sensor were also calculated and discussed.