Study On Preparation And Performance Of Deformation And Microcracks Visualized Flexible Sensing Materials

Structural health monitoring technology has gradually become an important mean of civil engineering infrastructure management and maintenance.Long-term monitoring of the structure can provide early warning of the structure health,and improve the reliability and service life of the structure by repairing damaged parts,which is of great practical significance to avoid the occurrence of major construction accidents.With excellent sensitivity,durability,mechanical flexibility and other advantages,flexible film damage monitoring smart sensor materials provide a new direction for structural health monitoring.In this thesis,the performance of the polymer substrate of the flexible film smart sensing material for damage monitoring was first investigated experimentally.By adjusting the preparation parameters of the polymer substrate,the thickness of the polymer film was analyzed.And the tensile mechanical properties were tested to study the effect of preparation parameters on the tensile properties of polymer substrates.Through experimental exploration,it was found that the selected polymer substrate has excellent light permeability and good self-cleaning performance,which laid the foundation for the preparation and research of flexible sensing materials.The performance was investigated based on the strain thin film resistance sensing material with nanoscale patterns.Mechanical properties such as stretching,bending and interfacial adhesion were explored through experiments.And the mechanical stability,durability and repeatability of the surface resistance under different load forms were analyzed.The effect of ambient temperature on the sensing performance of the patterned strain film sensing material was studied.And the influence of environmental factors on the surface resistance of the sensing material was analyzed.The sensitivity and applicability of the patterned strain film sensing material applied to structural deformation of steel specimen were experimentally investigated,and the functional relationship between the surface resistance value of the patterned sensing material and the structural strain was established.The performance was investigated based on the film visual angle sensing material with nanoscale grating pattern.The periodicity of the surface structure color and the change rule of the surface color under different viewing angles were studied by testing the reflection spectrum of the surface structure color under different viewing angles.It was found that the film visual angle sensing material with nanoscale grating pattern has four periods under different horizontal viewing angles,and the principle of periodicity was analyzed.Through experimental investigation,it was found that with the increasing of the observation angle,the surface structure color of the thin-film visual sensing material showed a blue shift phenomenon,and based on the experimental data,the relationship between the reflection wavelength peak of the thin-film visual sensing material and the observation angles was proposed.The performance was investigated based on the micro-scale self-reactive microcapsule deformation visual sensing material.The influence on the performance of microcapsules was explored by adjusting the preparation parameters,and the functional relationship between the rotation speed and microcapsule particles was established.Through the peak change of the infrared absorption spectrum and the ultraviolet-visible absorption curve,the successful encapsulating of the microcapsule visual sensing material and the sensing principle of the color change of the microcapsule caused by the dye's characteristic lactone ring structure from closing to opening were explored.The applicable ambient temperature was explored through experiments,and it was found that the visualized microcapsules prepared under different rotation speeds could maintain the stability of the microcapsule structure after heating for 12 hours at 50?.Under different load conditions such as stretching and fracturing,the microcapsule visual sensing material can provide early warning of structural damage through obvious color changes.Finally,it was applied to the application of micro-crack damage monitoring in concrete structures to detect its applicability and sensitivity.When the observation distance reaches 1 meter,the color change of cracks on the concrete surface can still be visually observed,indicating that the visual microcapsules have potential application value in the monitoring of micro-cracks on the surface of concrete structures.