Design And Research Of Structural Health Monitoring Method Based On Armor Composite Material

In the long-term use of sandwich armor composites,damage such as delamination,interlayer delamination and cracks may occur,which will produce structural damage,reduce the residual strength and fatigue performance of the material,bring about serious accident hazards and reduce the protection capability if not detected and repaired in time.Among them,delamination damage and impact damage are the main forms of damage to armor composites,and it is important to monitor and study them.In this paper,we take armor composites as the research object,build a structural health monitoring system according to the mechanism of the influence of damage on Lamb wave propagation in the structure,and realize the monitoring and positioning imaging of the damage.The main contents of this paper are as follows:(1)The multi-mode and dispersion characteristics of Lamb wave propagation in armor composites are investigated,the group velocity in each direction in the structure is studied experimentally,and the Lamb excitation mechanism and signal selection and attenuation characteristics are analyzed.(2)The hardware and software of the system are introduced.The simulation methods of delamination damage and impact damage in the armor composite are studied and verified by experiments.(3)A monitoring method for damage scattering signal based on phase delay retime-reversal localization imaging is studied,and the time-frequency characteristics and practical applications of Shannon continuous complex wavelet function(e.g.,extraction of narrow-band signals,group velocity calculation)are analyzed;theoretical derivation of different manifestations of multiple signal classification algorithms is carried out for different cases of shocks occurring in the far-field and near-field regions,and the difficulties of near-field shock location localization in array signal processing are solved.(4)The single damage and multiple damage monitoring and positioning experiments were carried out in 200mm*200mm*5mm armor composite material,and the monitoring and positioning imaging could be effectively carried out by time reversal algorithm.Four piezoelectric sensors with an interval of 160 mm were set in the experiment,and the results showed that they had good positioning accuracy,and the radial error in single damage positioning was within 4.12 mm.The radial error of multiple damage location is within 5.39 mm.For the impact positioning experiment under near-field conditions,the array formed by 7 piezoelectric sensors with spacing of12 mm is set.In the monitoring and positioning of multiple signal classification algorithm,the distance error is within 6mm and the Angle error is within 3°.