Research On Mechanical-electric Response And Application Of 2-2 Type Cement-based Piezoelectric Composite Material

With the rapid development of construction engineering and information technology,the use of intelligent monitoring systems to implement online health monitoring of civil engineering structures has become a research hotspot.Compared with traditional smart sensing materials,cement-based piezoelectric composite material has higher electromechanical coupling coefficients,low cost,and acoustic impedance matching characteristics of concrete.In this paper,the cutting-casting method was used to prepare 2-2type cement-based piezoelectric composite material.Using MTS material universal testing machine and Separate Hopkinson Pressure Bar device,quasi-static compressive experiments and dynamic compressive experiments were carried out on cement-based piezoelectric composite material to study the mechanical-electric response,including frequency response characteristics,linear characteristics,and sensing characteristics after embedded in mortar concrete.1.Quasi-static compressive experiments were performed by using a MTS experimental device.The results show that the average compressive strength of 2-2 type cement-based piezoelectric composite material is 85.68MPa,and the average failure strain of the sample is0.58%,the stress-strain curves have good linear relationship before failure;Sensitivity calibration experiments show that the sample has a critical value of G point 31.4MPa,and the sample's quasi-static sensitivity is 120p C/N;Alternating loading and square wave loading experiments show that the sample has good mechanical-electric response,that is,good frequency response characteristics and linear characteristics,and has good durability.2.Impact compressive experiments were performed by using a SHPB experimental device,the results show that there is a critical value 190s^-1 for the resonant frequency and residual percentage of d₃₃ value.When the strain rate exceeds this point,the decrease rate of the residual percentage of d₃₃ value increases,and the resonance frequency decreases rapidly,and then returns to the original value;when the degree of electrical domain inversion is large,the impedance frequency curves of the piezoelectric ceramic appear disordered,f_s and f_p are not obvious.The electromechanical coupling coefficient K₃₃,the dielectric loss D,and the quality factor Q_m are similar to the changes in the resonance frequency,and the capacitance of the sample is basically unchanged at the test frequency of 1 k Hz,and the dielectric constant is stable basically.3.Carry out the impact compressive experiments of 2-2 type cement-based piezoelectric composite material,the results show that 2-2 type cement-based piezoelectric composite material has obvious strain rate effect.The sample has a critical value H_C point 258s^-1,when the strain rate is less than the critical value H_C,the force-electric response of the material has a linear relationship;When the strain rate exceeds the critical value H_C,the sample mechanical-electric response is non-linear,that is,the output electrical displacement of the sample increases slowly.4.Conduct quasi-static and impact compressive experiments on simple sensors,the results show that as a sensing material,piezoelectric composite material can respond to the stress changes inside the concrete structure,the electrical displacement value output by the simple sensor in theory is more than the actual value by about 5%to 10%.Before the simple sensor under load,it may be that the piezoelectric composite material and the concrete material are not in sufficient contact,so that there is a deviation in the electrical displacement signal,or consider the impact of the embedding depth on the output electrical signal.After more tests,the value should be corrected according to the embedding depth,so as to reflect the bearing of the concrete surface more accurately.