In this work, the second harmonic generation (SHG) technique based on embedded piezoelectric (PZT) sensors is developed for the defect assessment of concrete samples. Three different imperfection forms of concrete including internal capillary void during the curing process, cracking damage due to compression, and bending loads are examined and analyzed. Clear second harmonics are observed by Fourier transform of time domain signal, and the square of fundamental signal amplitude shows a linear relation with the second harmonic amplitude as theoretically expected. The nonlinear parameter presents a good distinction for samples in different states of three cases, indicating the well-round feasibility of SHG technique based on embedded sensors. In addition, the nonlinear parameter presents an excellent correlation with the variation of internal capillary void and cracks in concrete. The high sensitivity of the developed SHG technique is further validated through a comparison between the nonlinear parameter and two traditional linear parameters, namely the phase velocity of Rayleigh wave and the resonance frequency of vibrations. Experimental results in this study demonstrate that the embedded sensors are promising for the nonlinear ultrasonic nondestructive evaluation of concrete structures, particularly as a low-cost alternative of commercial ultrasonic transducers.

Multi-layered cement-based piezoelectric composites could enable accurate real-time detection of the concrete structure deformation induced by impact load. An analytical method for quantifying the impact response of the multi-layered cement-based piezoelectric composite is established based on the piezo-elasticity, and a general transfer matrix description for the composite with any number of layers is derived. The motion of the composite is decomposed into natural modes according to its physical significance of vibration modes. The mechanical and electrical solutions are obtained via the mode summation method and the virtual work principle. In order to give a clear demonstration, some numerical simulations are conducted to verify the validity of the theoretical analysis. Moreover, the current analytical method considers the electrode as an extra layer and evaluates the effect of its thickness and material on the performance of the multi-layered cement-based piezoelectric composite. It can be seen that the mathematical model presented in this article provides a rigorous tool for the analysis of the multi-layered cement-based piezoelectric composite and therefore could benefit the design of certain types of smart devices under impact load.

Cement-based piezoelectric composite, has been widely used as a kind of smart material in structural health monitoring and active vibration control. However, transient dynamic loads such as impact loads may cause serious damage to the composite. Considering the electrode layer effect, this paper aimed to investigate the theoretical response of a 2-2 cement-based piezoelectric composite sensor subjected to an impact load. The vibration behaviors are analyzed by using the mode summation method and the virtual work principle. To simulate the impact load, transient haversine wave loads are assumed in the numerical simulation. Close agreements between theoretical and numerical solutions are found for peak transient haversine wave loads larger than 500 kPa, therefore proving the validity of the theory. Moreover, the influence of the electrode material and geometrical parameters on the dynamic characteristics of this sensor are considered. The present work should be beneficial to the design of this kind of sensor by taking into account the electrode layer effect.

Cement-based piezoelectric materials are widely used due to the fact that compared with common smart materials, they overcome the defects of structure-incompatibility and frequency inconsistency with a concrete structure. However, the present understanding of the mechanical behavior of cement-based piezoelectric smart materials under impact load is still limited. The dynamic characteristics under impact load are of importance, for example, for studying the anti-collision properties of engineering structures and aircraft takeoff-landing safety. Therefore, in this paper, an analytical model was proposed to investigate the dynamic properties of a 2-2 cement-based piezoelectric dual-layer stacked sensor under impact load based on the piezoelectric effect. Theoretical solutions are obtained by utilizing the variable separation and Duhamel integral method. To simulate the impact load and verify the theory, three types of loads, including atransient step load, isosceles triangle load and haversine wave load, are considered and the comparisons between the theoretical results, Li’s results and numerical results are presented by using the control variate method and good agreement is found. Furthermore, the influences of several parameters were discussed and other conclusions about this sensor are also given. This should prove very helpful for the design and optimization of the 2-2 cement-based piezoelectric dual-layer stacked sensor in engineering.

In view of the general theory of elasticity and the dynamic theory of piezoelectricity, this paper investigates the dynamic behaviour of 2–2 cement-based piezoelectric composite subjected to the harmonic electric signal considering the electrode layers. By considering the electrode layers as the elastic layer, the dynamic solutions of the mechanical and electrical fields of this composite are obtained. Furthermore, good consistency is shown by comparing the theoretical results with the finite element method results, proving the validity of the theory. Moreover, the influence of certain parameters is discussed, which can help get the desired displacements and stresses. Finally, the analytical model established here works effectively and could benefit the design of this sort of cement-based intelligent equipment.