Sensing Properties Of Piezoelectric Fiber Composites With Embedded Interdigital Electrodes

Structural health monitoring is becoming more and more important in modern industry and is considered to be one of the most effective ways to improve the health and safety of engineering structures and to achieve long life and sustainable management of structures.There is a huge security risk.Traditional piezoelectric ceramics are brittle and hard,and are not suitable for curved structures.In recent years,type 1-3 piezoelectric fiber composites have received extensive attention due to their good flexibility.The electrode structure adopts surface interdigitated electrodes,which have orthotropic properties and can realize excitation and sensing in the guided wave direction.Due to the presence of an epoxy layer between the surface interdigitated electrodes and the fibers,the dielectric mismatch of the materials,the weakening of the electric field,and the existence of a dead zone under the electrodes are caused.In this paper,a structural scheme of piezoelectric fiber composites with embedded interdigital electrodes is proposed,and the influence of key parameters on the performance of piezoelectric fiber composites is analyzed.Combined with ultrasonic guided wave technology,the effect of piezoelectric fiber composites embedded with interdigitated electrodes on The excitation and reception performance of Lamb wave directions in the board provides theoretical support and technical guidance for the design of new piezoelectric sensors.The main contents of this paper include the following aspects:(1)The structural scheme of piezoelectric fiber composites with embedded interdigital electrodes is proposed,and the influence of its key parameters on its electric field distribution and electromechanical properties is studied.Based on the homogenization theory,the performance prediction of the mechanical and electrical performance parameters of piezoelectric fiber composites was carried out.The research results show that the electric field distribution of the piezoelectric fiber composite material with embedded interdigital electrodes is uniform,and the electric field strength is about 1.3 times that of the surface interdigitated electrodes.The driving strain increases gradually with the increase of the piezoelectric fiber volume fraction and decreases with the increase of the electrode spacing.The compliance coefficient decreases with the increase of the piezoelectric material volume fraction,and the piezoelectric strain coefficient increases with the increase of the piezoelectric material volume fraction.(2)The piezoelectric fiber material embedded with interdigital electrodes was prepared and polarized,and the performance test and microstructure and morphology characterization of the piezoelectric fiber composite material embedded with interdigital electrodes were carried out.The research results show that the SEM microstructure shows that the piezoelectric fiber composites prepared by the cutting-filling method have a compact structure,the conductive silver glue is fully filled as a whole,no obvious holes or gaps are found,and the compactness is good.good.The piezoelectric fiber composite with embedded interdigital electrodes has a capacitance of 810.9 p F,a dielectric loss of 0.1,and an impedance of 117.6 K(?).(3)The propagation characteristics of Lamb waves in the plate are studied,and the excitation and reception performance of the piezoelectric fiber composites with embedded interdigital electrodes on the direction of Lamb waves in the plate are studied.The research results show that the piezoelectric fiber composites with embedded interdigital electrodes are excited The frequency response is best at low frequencies,and the guided wave exhibits obvious directional characteristics during excitation and sensing.The amplitude of the guided wave signal along the length of the fiber is high,and the main lobe angle is about 50°.