Preparation And Performance Of Orthotropic Piezoelectric Composite And Sensor

Cement-based piezoelectric composite is very suitable for monitoring structure damage,deformation and internal stress changes in concrete structure for its good combination with concrete,fast response,high sensing accuracy and superior characteristic of dual functions of actuating and sensing.However,piezoelectric composite fabricated by cutting-casting from piezoelectric ceramics exhibits the transverse isotropy characteristic;which makes it unidentifiable to structural damage information from different directions.Therefore,it has very important practical significance to develop cement-based piezoelectric composites with orthotropic properties to realize the precise damage localization of concrete structure.In this paper,the 1-3 orthotropic piezoelectric composite is prepared by piezoelectric ceramic PZT-5 as function phase and polymer/cement as matrix phase based on cutting-casting and arrangement-casting methods.The piezoelectric properties,dielectric properties,mechanical and electrical coupling performance of 1-3 orthotropic piezoelectric composite under different influence factors are discussed.The results show that the piezoelectric strain constant and piezoelectric voltage constant of orthotropic piezoelectric composite do not change significantly,and dielectric constant and dielectric loss change irregularly,coupling effects of resonance frequency occur with the increase of column height;The piezoelectric strain constant of orthotropic piezoelectric composite increase with the width increase,the piezoelectric voltage constant is opposite.The dielectric constants increase while the dielectric losses decrease,besides,resonance frequencies changes to the low-frequency.The piezoelectric strain constants of orthotropic piezoelectric composite decrease slightly with the cement mass fraction increasing.The piezoelectric voltage constants,dielectric constants and dielectric losses change irregularly.The changing in cement mass fraction has little influence on electromechanical coupling properties.The piezoelectric strain constants and piezoelectric voltage constants of orthotropic piezoelectric composite increase significantly with the increase of piezoelectric phase parallel series,the dielectric constants decrease and dielectric losses increase.The resistance values of different width piezoelectric composite reduce with the increase of the parallel series.The orthotropic properties of 1-3 piezoelectric composites under different heights,different widths,different parallel series and different cement mass fractions are studies.The results show that the changing in column height and width has little influence on orthotropic characteristic,and the received voltage signal amplitudes in orthogonal directions increase slightly with the width increase.All piezoelectric composites of different cement fraction reveal orthotropic piezoelectricity and the received voltage signal amplitudes upgrade firstly than descending latter tendency with increasing cement fraction.The piezoelectric composites exhibit excellent orthotropic characteristic when the parallel series is greater than 3,and the received voltage signal amplitudes gradually increase.The constitutive equation of 1-3 orthotropic piezoelectric composites is built based on that of the piezoelectric ceramic through the coordinate conversion of relational matrix of piezoelectric phase in composite,and the reason for anisotropy in plane of orthotropic composites is analyzed.The orthotropic piezoelectric composites are encapsulated as orthotropic sensors.The response rule and signal attenuation in plane of orthotropic sensors are studied,and the sensors are used for preliminary damage location test for acoustic emission signal damage.The results show that orthotropic piezoelectric sensors exhibit significant orthotropic piezoelectricity,high detection sensitivity and broad frequency bandwidth.The received AE signal amplitude curves and voltage curves both tended to be cosine shapes with the distance and angle changing.The received AE signal amplitude curves and voltage curves both decrease rapidly with increase the distance,and the farthest possible testing distance is 650 mm.The received signal amplitudes on the concrete surface are lower than that on glass surface,and the orthotropic characteristic remains stable.The repeatability of orthotropic piezoelectric sensor is good.Linear location testing on the concrete for orthotropic piezoelectric sensors show that the orthotropic piezoelectric sensors has satisfactory diagnosis accuracy.