【作者】 吕泳；

【导师】 李卓球；

【作者基本信息】 武汉理工大学 ， 固体力学， 2011， 博士

【摘要】 课题研究来源于国家自然科学基金项目“核安全壳应力监测的复合敏感层传感机理及其成像”,围绕着树脂基碳纤维复合材料的力阻效应,开展碳纤维智能束的研制工作,并对碳纤维智能束的功能特性进行了深入研究。具体研究内容包括碳纤维及其复合材料的力阻效应实验研究、碳纤维智能束的研制开发、碳纤维智能束的传感性能及其传感机理研究、开展基于碳纤维智能束的电阻模态的探讨、并进行了理论分析与实验验证。主要获得了以下几个方面的研究成果：(1)通过碳纤维单丝与碳纤维束的力阻效应研究,分析了无基体碳纤维材料电阻变化的规律与影响因素。通过实验分析发现碳纤维的应变-电阻灵敏度通常不超过2,纤维受外力作用时几何尺寸与电阻率的变化均导致电阻值发生改变,且尺寸变化导致电阻改变的权重高于电阻率变化。(2)以实验分析为突破口、通过研究不同碳纤维复合材料制作工艺、树脂改性添加剂使用量等对碳纤维智能复合材料力阻效应影响,在此基础上研制出一种高应变-电阻灵敏度的树脂基碳纤维智能束材料。(3)结合微观试验分析,发现碳纤维智能束中存在一定数量的纤维对接或者搭接而形成的“接触”节点,材料在受外载作用时,此类节点在小应变情况下就能脱离导电网络,导致电阻增大。综合考虑导致碳纤维智能束电阻变化的三方面因素,利用正态分布描述初始纤维接触点情况,采用Weibull模型描述后期纤维断裂情况等概率事件,结合(1)中结论,构建了碳纤维智能束的导电机理模型。(4)全面考察了碳纤维智能束的静、动态传感功能特性及其温度效应。结果表明其灵敏度高但离散性较大,总体的线性度较高、重复性较好、长期性能稳定、蠕变与零漂也较小,极限动态感应频率高。发现碳纤维智能束低于20℃时表现为NTC效应,高于20℃时则为PTC效应。(5)利用碳纤维智能束电阻-应变的关系,通过电阻分布来反映结构的动态特性,建立了以材料电阻为主要研究对象的模态分析方法。以悬臂梁为分析模型,计算出其位移模态、应变模态、电阻模态的理论解。在Ansys分析软件中通过将模态分析结果以约束的方式施加到结构上,再进行力电耦合场分析计算,实现电阻模态的有限元求解,为其进一步应用于复杂结构奠定了基础。(6)在理论分析基础上,从适用性方面开展了碳纤维智能束的结构模态实验研究。实验测得悬臂梁有无质量块两种工况下得到的位移模态、应变模态、电阻模态,结果表明电阻模态与应变模态对应力集中产生局部应变变化比位移模态更敏感。更多还原

【Abstract】 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.更多还原