Electromechanical Coupling Model Of Carbon Fiber Reinforced Composites Under Quasi-static Load

Nowadays,Carbon Fiber Reinforced Plastics(CFRPs)have been widely used in military,commercial and civil fields because of their light weight,high strength,and corrosion resistance.Through years of development,CFRPs have gradually become the main load-bearing structural material in the above-mentioned fields.However,the overall structural performance of CFRPs are reduced due to external forces in service.And the problems of CFRPs life prediction and structural health monitoring have not been effectively solved,which course equipment manufacturers have to cautiou about the introduction of CFRPs as the main load-bearing structure.Due to the anisotropy characteristic of CFRPs,the damage form is significant different from traditional metallic materials,which brings difficulties to the damage detection of the material.Thanks to the electrical conductivity of carbon fiber,Eddy Current Testing(ECT)technology with the advantages of contactless,non-radiation and low-cost has been employed in this thesis to realize the early warning of structural damage and life prediction of CFRPs under quasi-static load through full-cycle health monitoring,and to ensure the safety and reliability of structural parts.This thesis mainly studies the characterization of digital electromagnetic parameters under external load.First,through theoretical analysis and finite element modeling,the electro-mechanical coupling model of CFRPs is obtained.It is found that under bending load,CFRPs undergo bending deformation,and the internal fibers are broken and then wrapped,which changes the electrical properties of CFRPs.This is also the main influencing factor of the electrical properties of CFRPs during the stretching process.Therefore,the electro-mechanical model of CFRP was established from the macro-scales and micro-scales.Verified by the simulation and experimental results,the electromechanical coupling model proposed in this thesis can effectively characterize the variation law of electrical impedance of CFRPs in tensile and three-point bending tests.Secondly,three-point bending and one-way tensile tests for CFRPs have been done in this thesis.In the three-point bending test of unidirectional laminated and three-dimensional woven CFRPs,the primary sensor was improved to overcome the sensitivity of the detecting system has been significantly improved.When the CFRP is unidirectionally stretched,an 8-coil array-sensor that is sensitive to damage is designed.The sensors array can be used to monitor the damage of CFRP,and combined with the linear backprojection algorithm,the damage location can be accurately extracted.