Design Of Three-dimensional Braiding Piezoelectric Composite Actuator And Analysis Of Damage Mechanical Properties

Piezoelectric composite actuators have been widely used in many advanced technical fields,such as aerospace,civil engineering,precision equipment,and micro-electromechanics,etc,due to their high piezoelectric properties,high strength,and strong resistance to deformation.At present,the forming and manufacturing of piezoelectric actuators mainly use piezoelectric ceramic materials.Although piezoelectric ceramic actuators have good piezoelectric properties,they still have the fatal shortcoming of high brittleness.The current piezoelectric composite actuators have improved the brittleness of traditional piezoelectric ceramic actuators,and have the better flexibility of the polymer phase,but have interface problems.Due to the weak bonding force between the reinforcing phase and the matrix phase of the piezoelectric composite material,when it is in the working state,the interface between the two phases is not firmly bonded,which will easily cause the internal structure of the piezoelectric layer to fracture and cause the capacity of mechanical and the electric load is reduced,and it cannot continue to work,which leads to a decrease in the safety and reliability of the piezoelectric composite actuators.In order to solve the problem of the brittleness of the piezoelectric composite material actuator and the weak bonding force between the interface layers,this paper introduces the three-dimensional(3D)braiding process into the design process of the piezoelectric composite material actuator,starting from the structural design,and improving the current performance of the piezoelectric composite material,thus creating a new type of three-dimensional braided piezoelectric composite actuator(3D-BPCA).Compared with traditional piezoelectric actuators,the mechanical load-bearing capacity of the 3D-BPCA has been significantly enhanced,and the actuating performance has been improved.The research content of this paper is mainly divided into the following points:(1)On the basis of the 3D four-step braiding process,a detailed analysis and introduction of the motion law of the yarn carrier of the braiding machine tool of the three-dimensional braiding piezoelectric layer(BPCL)of the 3D-BPCA and the mechanical force analysis model of the BPCL are carried out.Starting from the law of periodic motion and buckling state of the fiber bundle during the braiding process,the macroscopic geometric model of the 3D-BPCA and the representative volume unit(RVU)model of the BPCL are established.With the aid of finite element numerical simulation,the validity and applicability of the model is verified,which also provides a theoretical basis for the subsequent analysis of the electromechanical coupling properties of the 3D-BPCA.(2)Based on the analysis of the mesoscopic theory and the electromechanical coupling field theory of the BPCL,combined with the mechanical and electrical periodic boundary conditions of the RVU,the elasticity of the piezoelectric composite layer is calculated.Constant,piezoelectric constant and dielectric constant,and then studied the changes in the actuating performance of the 3D-BPCA and the pure piezoelectric ceramic actuator under different fiber volume fractions.(3)Under the premise of analyzing the failure criterion of composite materials and the damage evolution equation,the progressive damage failure process of the3D-BPCA under the electromechanical coupling field is studied systematically.Based on the finite element theory method,the numerical changes of stress and strain during the damage and failure process of the 3D-BPCA are analyzed and compared with the pure piezoelectric ceramic actuator.At the same time,the influence of different volume fractions on the mechanical properties of the 3D-BPCA under the damage state was studied.