基于碳纳米纸传感器和深度学习的碳纤维复合材料损伤监测

纤维增强树脂基复合材料损伤机理复杂,为保证其长期稳定应用,需要采用先进的健康监测技术对其进行损伤监测。基于碳纳米纸传感器可灵敏监测电阻变化,对碳纤维增强聚合物(carbon fibre reinforced polymer composite,CFRP)复合材料进行冲击损伤监测,并设计出一套基于人工神经网络(artificial neural network,ANN)深度学习算法的损伤监测系统。通过数据分析可知,该系统可长期有效地监测CFRP的损伤发生与位置预测,且损伤位置精确度高达92%。该损伤监测系统可实现对复合材料健康状况的评估。

纤维增强复合材料静动态拉伸形变的碳纳米纸传感器监测

碳纳米纸可用作应变传感器监测纤维增强复合材料在静动态拉伸状况下的变形问题,这主要是通过测量与玻璃纤维增强复合材料一体固化成型的碳纳米纸传感器电阻变化来实现。试验结果表明,静态拉伸试验中,碳纳米纸传感器具有非常灵敏的应变传感性,在0~11 021με的应变范围内,其应变传感系数可达到22.1,在弹性极限点位置（应力为210MPa）电阻变化率发生突变;拉-拉疲劳试验中,当最大拉伸应力（215 MPa）大于弹性极限时,残余电阻变化率随疲劳周期增加明显加快;碳纳米纸传感器具有非常好的应变监测同步性和稳定性,完全可满足复合材料结构健康监测需要。

基于碳纳米线传感器的三维六向编织复合材料内部损伤定位

为研究三维编织复合材料的实时结构健康状态监控,针对三维六向编织复合材料编织结构,采用三维四步六向编织方法将碳纳米线传感器以轴向纱和六向纱形式嵌入复合材料中,提出了一种构建智能三维复合材料的方法,建立了基于碳纳米线的三维编织复合材料试件内部损伤监测系统。基于碳纳米线测量的电阻值矩阵,采用四分矩阵奇异值分解方法分析信号矩阵的主要特征,计算试件内部的损伤准确位置。实验采用5种不同类型损伤试件进行分析,结果表明,该方法计算的试件内部损伤位置与实际损伤一致,测量的损伤位置坐标误差小于1。该研究可为智能三维编织复合材料的健康监测发展提供理论基础。

空气热循环下基于碳纳米纸传感器的复合材料健康监测

将碳纳米纸传感器与玻璃纤维预浸料共固化一体成型的复合材料试验样件,在空气热循环的条件下进行处理,以此证明碳纳米纸传感器在特殊环境下依然具备良好的监测性能。复合材料试验样件在20℃到150℃的空气热循环处理之后,进行静态拉伸实验和1500次循环的拉-拉疲劳实验。在静态拉伸实验下,经过不同次数的空气热循环处理,产生损伤时碳纳米纸传感器的电阻变化率与应变随着热循环次数的增加而下降,但是传感器依然可以监测复合材料的损伤。在拉-拉疲劳实验下,传感器展现了良好的耐久性。经过150次的空气热循环处理之后,传感器的残余电阻仅轻微上升,进一步证明了碳纳米纸传感器在特殊环境下卓越的服役性能。

基于碳纳米纸传感器的复合材料结构低速冲击损伤监测

针对复合材料对冲击载荷比较敏感、内部损伤不易发现的问题,提出一种利用碳纳米纸薄膜作应变传感器的复合材料结构件低速冲击损伤监测方法。在拉伸条件下,对圆形和矩形碳纳米纸薄膜进行不同方向的传感系数测试,发现圆形碳纳米纸传感器具有较高且稳定的传感系数155.63,可以作为全向传感器监测冲击损伤。复合材料结构的冲击损伤由传感器的电阻变化率和超声C扫描结果同步表征。研究结果表明,传感器的电阻随着冲击能量的增加而增加,基于全向碳纳米纸传感器的结构健康监测不仅可以灵敏感知低速冲击损伤,为损伤程度评估提供客观数据,而且通过分析不同方向BP传感器的电阻变化可以判断损伤位置。进一步与传统C扫描结果相比较表明,全向碳纳米纸传感器可以有效预判低速冲击损伤,用于航空航天复合材料结构件的实时在线健康监测。

湿热环境下复合材料基于碳纳米纸传感器的低速冲击损伤监测

针对湿热环境下复合材料的低速冲击损伤监测,将碳纳米纸传感器与复合材料一体成型,对湿热处理后的复合材料进行低速冲击。在由低到高的能量冲击下,传感器的电阻变化率呈阶梯性变化,多次冲击后传感器性能依旧稳定。此外,在冲击位置以及材料裂纹扩展方向传感器的电阻变化率比其他位置大,传感器展现了优良的冲击损伤定位能力。结果表明,碳纳米纸传感器能够在湿热环境下检测低速冲击损伤,并可以通过传感器阵列进行低速冲击损伤定位。

基于新型碳纳米纸传感器对VARI工艺中树脂流动趋势的实时监测

采用喷射吸附过滤成形工艺获得一种高柔性、高灵敏度的碳纳米纸(BP)传感器,碳纳米纸传感器是由碳纳米管在分子间范德华作用力条件下形成的三维介孔结构的薄膜材料。碳纳米纸传感器可嵌入在复合材料预成形体铺层中,与复合材料一体成形,实时监测真空辅助液体复合成形(VARI)树脂的流动情况。结果表明,通过在线监测系统采集在树脂浸润过程中碳纳米纸传感器的电阻,可准确监测树脂流动到相对应的位置的时间,以此来判断树脂浸润过程中的流动趋势。本文证明了碳纳米纸传感器可以实时监测VARI工艺中树脂的动态行为,为避免VARI工艺中由树脂浸润造成的缺陷,改进工艺参数以及优化生产等提供了新的途径。

三维编织复合材料弯曲承载下嵌入碳纳米线的特性分析

为实现三维编织复合材料实时承载监测,基于碳纳米线嵌入三维编织复合材料预制件的方法,研究了嵌入碳纳米线三维编织复合材料制件在三点弯曲试验中碳纳米线的应变特性。结果表明:在三点弯曲过程中,制件加载至断裂碳纳米线的电阻变化具有单调一致性,碳纳米线电阻变化符合一定指数函数关系;在大负荷加载后碳纳米线产生电阻滞后现象;制件卸载后,碳纳米线传感器产生残余电阻。研究结果证明:碳纳米线传感器在弯曲承载下能够实时监测三维编织复合材料结构健康状况,为三维编织复合材料结构健康监测系统的构建提供了参考。

Mg^(2+)功能核酸生物传感器检测技术的研究进展

Mg^(2+)是人体内重要的二价金属阳离子之一,在催化细胞核酸的相关反应中具有重要的作用。在人体体内Mg^(2+)的缺失或过量会对人的健康带来危害。同时,Mg^(2+)在自然环境中也有多种作用。因此Mg^(2+)的检测受到了人们的重视。其中Mg^(2+)的仪器检测技术已经发展成熟,但也存在着一些弊端。而近些年,人们发现了功能核酸具有序列易修饰、特异性高、稳定性高、成本低,以及和生物传感器联用可实现现场快速检测等优势,功能核酸也逐渐引起广泛关注。现阶段,针对Mg^(2+)已建立多种特异性功能核酸生物传感器,实现了对多种生物标志物进行检测。与新型纳米材料的结合更加提高了检测极限以及检测的广谱性。首先介绍了Mg^(2+)功能核酸的作用方式和规律、体外筛选方法和结构性质,并对Mg^(2+)特异性功能核酸传感器的组建原理以及应用进行了综述;其次根据Mg^(2+)功能核酸传感器中信号放大的方式以及与不同纳米材料结合进行了分类,包括变温传感器、恒温传感器、金纳米传感器、碳纳米传感器等。主要内容涉及传感器的具体传感原理、适用领域、灵敏性以及检测限的比较;最后对Mg^(2+)功能核酸在食品和生物医学方面的应用进行了归纳,并对存在的不足以及未来应用进行了展望,旨在为今后研发更便携、更灵敏、更准确的生物传感器奠定理论基础。

碳纳米线在三维编织复合材料健康监测中的应用

对三维编织复合材料健康监测技术的现状进行分析,提出采用四步法三维编织技术将碳纳米线与复合材料共同编织形成智能复合材料;对复合材料预制件进行拉伸承载实验,实验数据表明预制件的编织角和碳纳米线织入间距是影响健康监测的重要因素.实验结果说明了碳纳米线传感器作为一种新的综合和分布式技术应用于复合材料制件的健康检测的可行性.

碳纳米线的拉伸应变传感特性

为开发用于三维编织复合材料原位结构健康监测的碳纳米线传感器,建立了碳纳米线应变传感实验系统,通过纵向拉伸实验,分析了碳纳米线的力学性能(应力和应变)与电性能(初始电阻和应变灵敏系数)之间的关系,并对性能参数进行了Weibull统计分析,系统研究了碳纳米线的应变传感特性。结果表明:纵向拉伸负载期间,碳纳米线相对电阻变化与应变呈现良好的线性关系;碳纳米线具有与传统应变监测相当的应变灵敏系数,适合用于监测破坏极限应变远小于碳纳米线应变(碳纳米线的破坏应变均值为10.0%,最小值为2.5%)的复合材料的损伤,是复合材料结构健康监测传感器的良好候选材料。

三维编织复合材料健康监测数据异常诊断研究

分析了三维编织复合材料试件结构健康监测技术现状,提出了碳纳米管在三维编织复合材料试件健康监测的应用方法。基于滑动窗口,提出了一种数据流异常检测的算法,对数据进行分析和损伤状态判定。结果说明碳纳米管应用于三维编织复合材料整体结构监控是可行的。该算法计算结果与实际损伤具有很好的吻合性。为内置碳纳米管传感器应用于复合材料制件的实时健康监测提供一种新的综合和分布式技术。

飞机结构健康监测方法发展现状评述以及展望

在民用飞机结构设计过程中,由于复合材料自身所具备的特点而获得了广泛的使用,因此对其从生产至服役这一全寿命周期进行健康监测显得尤为重要。本文概述了现阶段常用飞机结构健康监测的原理与方式方法,同时介绍一种新型的碳纳米健康监测传感器,并对结构健康监测结束发展进行展望。

Affinity and fluorescent detection of surfactants/ssDNA and single-walled carbon nanotube

A new biosensor platform was explored for detection of surfactant based on fluorescence changes from single strand DNA （ssDNA） and single-walled carbon nanotubes （SWNTs）. Thermodynamics assay was performed to value the stability of probe. The affinities of SWNT to five common surfactants （SDS, DBS, Triton X-100, Tween-20 and Tween-80） were investigated by real-time fluorescence method. The effects of Mg^2＋ and pH on the fluorescence intensity of self-assembled quenched sensor were performed. The fluorescent emission spectra were used to measure the responses of self-assembled quenched fluorescent of ssDNA/SWNTs to different concentration surfactant（Triton X-100）. The FAM-DNA wrapped SWNTs probe was stable in a wide temperature range （5 ℃ to 80℃）. The binding strength of surfactants and single-stranded DNA （ssDNA） on SWNTs surfaces was shown as follows： Triton X-100〉DBS〉Tween-20〉Tween-80〉ssDNA〉SDS, and the optimized reaction conditions included pH 7.4 and 10 mmol/L Mg2＋. The fluorescence of FAM-ssDNA wrapped SWNTs was proportionally recovered as a result of adding different concentrations of Triton X- 100, which realizes the quantitative detection of Triton X- 100.

Acceleration sensing based on piezoresistive effect of carbon nanotube films

Based on piezoresistive effect, the acceleration sensitivity of multi-walled canbon nanotube (MWNT) films was investigated. A three-point bending technique was presented to measure the piezoresistivity, which used a bending stress applied to the samples while making MWNT films wheeling with a rotational machine. The experimental results showed that the fractional increase in resistance increases linearly versus the increase of centripetal acceleration, and there is a linear relationship between the acceleration and the strain. These shed light on using carbon nanotube films as acceleration sensors for many potential applications.

基于主成分分析的智能复合材料结构损伤类型识别

针对三维编织复合材料制件结构状态监控的关键问题,提出了基于三维六向编织工艺将碳纳米管纱线嵌入到整体复合材料制件中,构建三维空间结构的智能复合材料的方法,利用损伤指数实现了对智能复合材料制件内部损伤类型的识别,并分析了4组三维六向编织智能复合材料制件的损伤指数表现特征。结果表明:综合损伤指数优于其他3种损伤指数,综合损伤指数可精确识别制件内部损伤的类型;对于三维编织复合材料制件内部空隙类微小损伤,综合损伤指数监测值小于100;对于制件内部裂纹的损伤,综合损伤指数监测值位于300～500;当综合损伤指数监测值大于600时,可判断为试件存在大裂口损伤;基于损伤指数可计算制件内部损伤大小,精度可达到0.073 mm。

Effect of Electron Drag on Performances of Carbon Nanotubes as Flow Sensors

Experimentally, the electron drag effect on carbon nanotube surface in flowing liquids was investigated. It was found that electric current could be generated in metallic carbon nanotubes immersed in the liquids. Carbon nanotubes were synthesized on Si substrate by hot filament chemical vapor deposition. The experimental results showed that the flow-induced current on the surface of carbon nanotube films was closely depended on the flow rate, concentration, properties and temperature of liquids. The flow-induced current was increased with the increasing of flow rate, concentration and temperature of liquids. The obtained results were discussed in detail.

Piezoresistive Sensors Based on Carbon Nanotube Films

Piezoresistive effect of carbon nanotube films was investigated by athree-point bending test. Carbon nanotubes were synthesized by hot filament chemical vapordeposition. The experimental results showed that the carbon nanotubes have a striking piezoresistiveeffect. The relative resistance was changed from 0 to 10.5 X 10^(-2) and 3. 25 X 10^(-2) for dopedand undoped films respectively at room temperature when the microstrain under stress from 0 to 500.The gauge factors for doped and undoped carbon nanotube films under 500 microstrain were about 220and 67 at room temperature, respectively, exceeding that of polycrystalline silicon (30) at 35℃.The origin of the resistance changes in the films may be attributed to a strain-induced change inthe band gap for the doped tubes and the defects for the undoped tubes.

Radiation-Induced Graft Polymerization of Sodium 4-Styrene Sulfonate onto Multiwalled Carbon Nanotubes and Their Application as Electrogenerated Chemiluminescence Biosensors

Sulfonate groups were introduced to the surfaces of multiwalled carbon nanotubes by the radiation-induced graft polymerization of sodium 4-styrene sulfonate for the use as biosensor supports. Alcohol dehydrogenase was immobilized onto a sulfonated nanotube-supporting electrode with tris（2,2＇-bipyridyl） ruthenium（II） complex to form an electrogenerated chemilluminesce sensor of alcohol. When it was used to detect alcohol in cyclic voltammetric measurements, the sensor showed the linearity over the range of 1.0 × 10^-4 M-5.0 ×10^-2 M, with a correlation coefficient of 0.992 and a detection limit of 1.9 ×10^-6 M. In electrogenerated chemilluminesce detection, it showed linearity over 5.0 × 10^-4 M-1.0 × 10^-2 M, with a correlation coefficient of 0.986 and a detection limit of 1.0 × 10^-6 M. The sensor was demonstrated to be able to detect ethanol in commercial drinks.

Laccase biosensor using magnetic multiwalled carbon nanotubes and chitosan/silica hybrid membrane modified magnetic carbon paste electrode

A simple and rapid strategy to construct laccase biosensor for determination of catechol was investigated. Magnetic multiwalled carbon nanotubes (MMCNT) which possess excellent capability of electron transfer were prepared by chemical coprecipitation method. Scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) were used to identify its surfacetopography and magnetization, respectively. Laccase was immobilized on the MMCNT modified magnetic carbon paste electrode by the aid of chitosan/silica (CS) hybrid membrane. Using current-time detection method, the biosensor shows a linear response related to the concentration of catechol in the range from 10-7 to 0.165×10-3 mol/L. The corresponding detection limit is 3.34×10-8 mol/L based on signal-to-noise ratios (S/N) ≥3 under the optimized conditions. In addition, its response current retains 90% of the original after being stored for 45 d. The results indicate that this proposed strategy can be expected to develop other enzyme-based biosensors.