Research On Self-monitoring Method Of Stress And Strain In Continuous Carbon Fiber Wound Structure

As a lightweight reinforcing fiber material,carbon fiber has been widely used in many important engineering fields.At the same time,due to the characteristics of piezoresistivity and thermal resistance effect,carbon fiber is expected to be a good self-sensing smart material,which enables existing composite structures to achieve stress strain,temperature and other essential physical parameters self-monitoring without the need to embed external sensors.On the other hand,as carbon fiber composite materials are increasingly applied to important pressure-bearing structures such as pressure vessels and pipelines,the monitoring of stress,strain and damage is directly related to the safety of industrial production,which has become an urgent issue.Based on this,the paper carried out self-monitoring research on continuous carbon fiber wound structure,and explored the piezoresistivity characteristics,sensing mechanism and stress-strain self-monitoring method of carbon fiber in cylindrical curved surface structure.Firstly,the sensing performance and the piezoresistivity effect of continuous carbon fiber bundle were studied.Basic sensing characteristics experiments show that it has good volt-ampere characteristics,and the resistance value reaches a steady state after being energized for 30 minutes.Then through the uniaxial tensile test,it is found that the whole process can be divided into three stages,including pre-stretching,stretching and breaking stage.After that,the carbon fiber bare bundle and the resin-based carbon fiber samples were respectively subjected to cyclic tensile test,the results of which both show a good piezoresistivity effect.The sensitivity coefficient of the carbon fiber bundle was 0.8274 according to the load and resistance data of tensile phase.Secondly,the internal pressure sensing performance of a single-layer continuous carbon fiber wound thin-walled cylindrical structure is studied.Initially,the relationship between the internal pressure-strain-fractional changes in electric resistance is obtained by analyzing the force and geometric deformation of the structure.The experimental results show that the error between the self-monitoring result and the actual internal pressure is 3.09%at the winding angle of 84°.Thirdly,the axial pressure sensing performance of a single-layer continuous carbon fiber wound cylindrical structure was studied.Initially,the approximate Young's modulus of the structure is obtained by ANSYS simulation analysis,and then the relationship between the fractional changes in electric resistance of the axial compression-strain-resistance is obtained by static and geometric deformation analysis.At last,through the compression experiment,the self-monitoring result of the carbon fiber bundle winding angle of 87° and the actual axial pressure average error is 4.18%.Finally,the application of carbon fiber wound cylindrical structure in fluid system monitoring is discussed.A simulation experiment was carried out for both uniform deposition and partial clogging in the pipeline.The experimental results show that the fractional changes in electric resistance of carbon fiber can respond to changes in fluid parameters inside the pipeline.When there is deposition or partial clogging in the tube,the flow rate of the outlet will decrease,and the fractional changes in electric resistance of carbon fiber will increase.The study reveals the application prospects of carbon fiber in the health monitoring of hose structures.