Evolution of electromechanical properties of cement-based piezoelectric composite material under freeze–thaw cycles

The properties of cement-based piezoelectric (CBPZ) composite materials are significantly affected by freeze–thaw cycles (FTCs). In this study, a 2–2 CBPZ composite material was developed and the evolution laws of mechanical properties, electromechanical response characteristics and electrical properties under FTCs were investigated. Scanning electron microscopy was used to detect damage to the cement matrix, the piezoelectric functional phase and their interfaces. Variations in the diffraction intensities of piezoelectric functional phases were studied using X-ray diffraction and the numbers of domain transitions were estimated. The results confirmed that the piezoelectric strain constant, sensitivity coefficient, electric displacement and compressive strength of the CBPZ composites linearly decreased as the number of FTCs was increased. The piezoelectric voltage constant monotonically increased and the mechanical quality factor continuously decreased with an increase in the number of FTCs. The electric displacement–stress curves showed critical points that denoted transition points from linear to non-linear. Boltzmann functions were used to draw plots of electric displacement–stress and quasi-static stress–strain of the prepared material for various numbers of FTCs. The electric displacement degradation and freeze–thaw damage evolution laws as the number of FTCs was increased are also presented. The findings of numerical fitting agreed well with the experimental data, with a correlation coefficient that exceeded 93%.