Research On Dynamics-based Damage Detection Of Composite Plates

Carbon fiber reinforced composites have high specific stiffness and specific strength,and are superior to traditional materials in vibration damping,fatigue resistance,high temperature resistance and designability.They have broad application prospects in aerospace,construction,automotive and other fields..For composite structures,structural damage can occur during service due to external impact loads and long-term fatigue loading.And with the accumulation of damage,the degree of danger of the structure is gradually increasing.Therefore,a method of damage location can be found,which can help people take measures as early as possible to avoid sudden damage to the structure.In this paper,the health monitoring and detection of composite materials in service is taken as the engineering background.Based on the theory of vibration mechanics and piezoelectric drive mechanics,the research methods of theoretical analysis,numerical simulation and experiment are used to study the damage identification of thin plate structures.The main research contents are as follows:Firstly,the development of health monitoring technology at home and abroad is introduced.The various dynamics-based damage identification methods currently used are briefly introduced to explore the advantages and disadvantages of various methods.Secondly,the mechanical properties of composite plates and the theoretical methods for modal analysis of composite plates based on vibration theory are summarized.Then,taking the composite plate with the damage of the unit notch as an example,the damage detection of the X850 carbon fiber composite board was studied under the free boundary conditions of the four sides and the two sides.The surface-bonded piezoelectric ceramic(PZT)sheet was used to excite the plate structure,and its various modes were obtained and the damage position was identified by the curvature mode.Two sets of piezoelectric active structural health monitoring systems are used which they are lead zirconate titanate-laser Doppler vibrometer(PZT-SLDV)modal test system and lead zirconate titanate-polyvinylidene fluoride(PZT-PVDF)mode.These state test systems are used to test the composite plate structure.The preliminary preparation work and experimental operation steps of the damage identification of the thin plate by the two systems are introduced in detail.Based on the modal data measured by the above systems,the damage identification method based on the curvature mode is used for damage identification.The experimental results show that both systems can effectively identify the unit notch damage of the carbon fiber composite plate.Finally,using the ABAQUS finite element analysis software,the finite element analysis model of the damaged composite plate is established.The modal analysis of the finite element model established under two boundary conditions is carried out,and the vibration of the mode shape is calculated by the central difference method.The finite element simulation results are compared with the experimental results to verify the effectiveness of the analysis model.Furthermore,the finite element method was used to simulate the composite plates at different damage locations,and the influence of different damage locations on the damage identification using the curvature mode was analyzed.