Key Technology Of Metallic Package For Surface-mounted Fiber Bragg Grating Strain Sensors

Fiber Bragg grating(FBG)is widely used on the structures such as bridges,buildings,tunnels by virtue of light weight,small size and anti-electromagnetic interference.Because of small and fragile,FBG should be encapsulated to promote mechanical strength before using.The general packaging material is organic adhesive with aging and creep,which will affect the sensing accuracy and stability of FBG.However,metal materials can effectively overcome these problems,so that FBG sensors have a higher and more stable strain sensitivity,therefore,metallized package should be applied in FBG.But high temperature damage,bad adhesive uniformity and consistency are main problems existing in the methods of metallized package,which will influence FBG sensing performance,and large equipment,high cost and poor operation will limit its application.So,this study discusses FBG metallized package with the purpose of getting a high survival rate,high sensitivity and high consistency,in addition to that,easy-operation and low cost are necessary.Main research contents are as follows:(1)In order to make FBG less damage,make metallized package simple and feasible,the scheme of “surface metallization of FBG & super electroplating” is put forward based on electroplating principle,and derive FBG metallized process and electroplating process.(2)In order to make super plating possible,good FBG metallized process is required.,Chemical silver plating technology is presented.According to the traditional mirror-produced technology,and coating evaluation system is put forward from super plating needs.Additives and silver plating times are discussed by uniformity,compactness and binding force.Finally,the FBG metallized process is confirmed.(3)Super electroplating package is carried out based on FBG metallization.On the one hand,according to different strain application environments of FBG,three structures of the metal substrate are designed and simulated by COMSOL Multiphysics.On the other hand,the factors of super plating parameters are analyzed and super plating equipment is designed,at the same time,the super plating parameters of metal zinc are determined.(4)In order to evaluate the effectiveness of metallized package technology,FBG metallized package experiments were done.The strain transfer performance was evaluated through tensile testing and spectrum analysis.Besides,the organic glue package results are compared.The results show that the survival rate of FBG metallized package is 100%,FBG sensors have a higher sensitivity,consistency and repeatability,showing excellent strain transfer performance.