Dependent Characteristics Of Piezoelectric Effect Of Cement-Based Piezoelectric Material

Cement-based piezoelectric materials that are formed by cement base material with a certain amount of conductive phase, whose electrical resistivity changes in the process of loading and unloading. The feature of the materials can be used to monitor large-scale civil engineering structure effectively, and avoiding major disasters without warning. Currently, carbon fiber cement-based piezoelectric materials are widely used as which not only cost little but have a better sense of transfer and feedback. The current study of cement-based piezoelectric materials focuses on the piezoelectric effect under static load and cyclic load. While, there is little research about time-variant characteristic of the cement-based material’s piezoelectric effect which means the piezoelectric effect is under long term load.This paper chose the piezoelectric materials whose carbon fiber volume contents were 0.16%, 0.26% and 0.36%. Firstly, the paper researched on the piezoelectric effect under static load and cyclic load. Then, analyzing the creep property and piezoelectric effect of the carbon fiber piezoelectric materials in the same curing condition after 90 d load( Temperature is(20±2) ℃, relative humidity is(65±5)%). Lastly, this paper analyzed the interrelations between piezoelectric effect and creep property under the long term load. This study has found that the resistivity of cement base piezoelectric materials decreased to a minimum value and then increased with the increase of loading stress. The piezoelectric effect of materials with 0.26% fiber content was the most obvious one. The piezoelectric materials with different fiber contents had different sensitive internal under circulating load. For example, the sensitive internal of the piezoelectric material with 0.36% and 0.26% fiber contents was 0 to 15 k N, while 0.16% fiber content showed 0 to 10 k N. Besides that, piezoelectric effect is reversible within the range of piezoelectric interval. In the long term load, the Specific Creep of piezoelectric materials with different fiber contents didn’t appear to be much different under the same stress level. However, the materials that showed different piezoelectric effect have different time-variant characteristics. Materials with 0.36% and 0.26% fiber contents show the positive effect, that is the strain increased but resistivity decreased as time increased. While, 0.16% content shows passive effect, which means the strain and resistivity increased as time increased. For the same fiber content, The Creep deformation and piezoelectric effect is always different under different stress level. When the load stress was less than the ultimate load stress of sensitive interval, the piezoelectric effect is positive. Whereas, when the load stress is greater than or equal to the ultimate load stress, the piezoelectric effect is passive.