Functional Properties And Application Of Smart Polymer-matrix Carbon Fiber Bundle

The dissertation was supported by the project of National Science Foundation "The mechanism of compound sensitive surface and imaging method of stress monitoring for nuclear safety shells", around piezoresistivity of polymer-matrix carbon fiber composite material, carry out working on manufacture bundle of smart carbon fiber, to in-depth study the features of bundle of smart polymer-matrix carbon fiber bundle. Specific research includes the experimentals of piezoresistivity of carbon fiber and composite materials, research and development of smart carbon fiber bundle, the research of sensing performance and sensing mechanism of smart carbon fiber bundle, proposed the concept of resistance mode, and give the analysis theoretically and experimental verification. Mainly obtained in the following areas of research:Firstly, with analysis the law and factors affecting of variation resistance of carbon fiber without substrate, by the research about piezoresistivity of monofilament carbon fiber and carbon fiber bundle. Through experimental analysis discovered that strain-resistance sensitivity of carbon fiber is usually not more than 2, fibers by external force, the geometry and resistivity changes that are leading the resistance to change, and dimensional changes lead to resistance to change that much than the resistivity change.Secondly, in the experimental analysis as a breakthrough, through the study of piezoresistivity of carbon fiber composite used different carbon fiber composite material production process and resin modified additives, on the basis of this developed a high strain- resistance sensitivity of smart polymer-matrix carbon fiber composite materials, referred to as the smart carbon fiber bundle.Thirdly, combined with micro-test analysis, a certain amount of fiber overlap to form contact node, materials when subject to external loads, this node can be separated from the conductive network in the case of small strain, lead to resistance increased. Considering the three factors that caused changes in resistance of smart carbon fiber bundle, used a Normal distribution to describe the contact points situation of initial fiber, using Weibull model describes the events of probability of late such as fiber breakage, combined with the conclusion in (1), building conductive mechanism model of smart carbon fiber bundle.The fourth, comprehensive study of static and dynamic features of the temperature effect sensor of the smart carbon fiber bundle. The results showed high sensitivity but a large dispersion, high overall linearity, good reproducibility, long-term stable performance, creep and zero drift is less, high frequency of the limit dynamic sensor. Carbon fiber bundle is lower than 20℃smart for NTC effect, higher than 20℃for the PTC effect.The fifth, use the relationship of strain-resistance of smart carbon fiber bundle, reflect dynamic characteristics of the structure by resistance distribution, establish a modal analysis method that resistivity is the main object of study. Let cantilever for analysis model, calculate the displacement mode, strain mode, theoretical solution of resistance mode. To calculate the modal analysis results as the restrict way, applied to the electromechanical field in Ansys software package, achieve finite element analysis of resistance mode, for further applied to the complex structure laying a good foundation.Finally, on the basis of the theoretical analysis, carried out experimental study of structural mode of carbon fiber smart bundle from applicability. Experiment measured displacement mode, strain mode, resistance mode, under two kinds of conditions that while the cantilever working have mass or not, the results show that resistance modal and strain modal is more sensitive than the displacement mode, then stress concentration to produce local strain.