# Dynamic Response of Electro-Mechanical Properties of Cement-Based Piezoelectric Composites
## 4 Conclusions  
Using the ordinary Portland cement as the matrix and PZT-5H piezoelectric ceramics as the functional body, type 1-3 and type 2-2 cement-based piezoelectric composites were prepared in this study via the cutting-casting method. The electro-mechanical response characteristics of type 1-3 and type 2-2 under quasi-static and dynamic impact compression are studied. The following conclusions can be drawn:  
1. Under quasi-static compression, the sensitivity of type 1-3 and type 2-2 composites has a nonlinear mutation point (approximately 21.7 and 35.0 MPa, respectively). The linear range of type 2-2 is significantly greater than that of type 1-3 (by 61.3%).
2. Both type 1-3 and type 2-2 composites have strain rate effects and are strain rate sensitive materials. At a lower strain rate, the peak value of the output electric displacement increases as the strain rate rises; at a higher strain rate, the growth rate associated with the peak value of the output electric displacement slows down.
3. The stress relaxation time and strain rate exhibit an approximately negative linear correlation for both type 1-3 and type 2-2; that is, the relaxation time monotonously decreases with an increase in strain rate. The time required for type 2 to return to its normal state is lower after the external force is released.
4. Similar to the results obtained under quasi-static compression, the dynamic sensitivity of type 1-3 and type 2-2 also has electrical domain switching points (70.5 and 88.0 MPa, respectively). The linear range of type 2-2 is greater than that of type 1-3 (by 24.8%). Therefore, type 2-2 has certain advantages as a sensor material, regardless of whether it is subjected to quasi-static or dynamic loading.  
Figure 10: Calibration curve for dynamic sensitivity of the cement based piezoelectric composites.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter**Sample & **Linearity Range/MPa** & **Fitting Function** & **Correlation Coefficient R\({}^{2}\)** & **Sensitivity/(pC-N\({}^{-1}\))** \\ \hline
1-3 & 0–70.5 & \(D=0.000323\sigma-0.0014\) & 99.81\% & 323 \\
2-2 & 0–88.0 & \(D=0.000296\sigma+0.0082\) & 98.35\% & 296 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Linear fitting parameters of dynamic sensitivity.  
**Author Contributions:** Conceptualization, Y.L. and Y.Z.; validation, J.C. and C.S.; formal analysis, Y.L.; investigation, Y.L. and H.D.; data curation, Y.L. and W.C.; writing--original draft preparation, Y.L.; writing--review and editing, Y.L.; supervision, J.C.; project administration, Y.L. and J.C. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by Natural Science Foundation of China (Nos. 11572163 and 11832013), Ningbo Rail Transit (JS-00-SG-17003).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.  
**Data Availability Statement:** The data used to support the findings of this study are available from the corresponding author upon request.  
**Acknowledgments:** The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China and Ningbo Rail Transit Ltd.  
**Conflicts of Interest:** The authors declare no conflict of interest.