光纤传感器监测复合材料固化过程

设计了两种新型光纤传感器,一种是通过测量光纤末端近场模斑谱反映光纤埋置 脂折射率的变化,另一种行微弯衰减方法测量复合材料固化中铺层被压缩的进程。利用这两种传感器进行了复合材料固化监测实验,结果表明,发现光纤模斑传感器的信号可以反映树脂基体的粘度的变化历程,光纤微弯传感器的信号可以反映铺层被压缩的过程,监测这两个关键的参数变量不但有利于操作工艺的优化,而且为建立复合材料因化过程的智能化在线监控系统奠     

用于FRP固化在线监测的光纤微弯压力传感器

无论在军事还是航空航天领域,光纤传感器都是一种极具应用前景的智能化监测手段。目前,将光纤传感器用于纤维增强树脂基复合材料固化过程的监测的研究是一个热点。但由于大多数光纤传感器监测固化过程成本较高,所以还没有被广泛的应用于实际生产当中。开发了一种新型的低成本、高灵敏度、易操作的光纤传感器用于纤维增强树脂基复合材料固化过程的在线监测。光纤传感器的设计基于光纤微弯损耗原理,其监测的直接目标参量为增强纤维所构成的网络所承担的压力变化,可以进而通过Gutowski的树脂流动/纤维变形理论间接得出对于固化过程中的几个关键参量。给出了这种压力传感器的设计制作方法,测定该种传感器在静态和动态下的压力-光损耗响应曲线,分析了该传感器对环境温度与折射率变化的响应。完成了利用微弯压力传感器进行纤维增强复合材料在热压釜中固化成型过程的在线监测实验,获得了良好的结果。     

光纤模斑传感器应用于在线监控复合材料工艺过程

复合材料的固化有着复杂的内部过程, 传统的工艺条件难以保障产品的质量, 发展智能化的在线监控技术是个有效途径, 在线监控系统需要有先进的传感器。研制了一种新型光纤传感器, 提出通过测量光纤末端近场模斑谱反映光纤埋置周围树脂折射率的变化。给出了利用这种传感器进行复合材料固化监测的实验结果。发现这种光纤传感器的信号能反映固化凝胶点、固化结束点及树脂粘度的最低点, 又由于光纤与复合材料的兼容性好以及装置简单、廉价、可靠性高, 因此可以应用于复合材料固化过程的在线监控系统。     

基于折射率变化的固化在线监测研究

先进复合材料的固化成型工艺十分复杂,目前在很大程度上仍依赖于经验工艺。为了实现复合材料固化工艺的透明化、科学化及智能化,提出了将光纤折射率传感器用于复合材料制造过程,研制了一种折射率光纤传感器,同时将光源、探测器、信号处理器等元器件集成化为一个便携式的光纤传感仪以利于生产现场使用。利用该传感器对常温固化树脂的固化过程进行了测量,将其与同等条件下迈克尔逊干涉仪对固化过程的监测结果进行了比较,二者具有良好的一致性。在实验室与生产现场两种条件下将光纤折射率传感器埋设于预浸料中对其固化工艺过程进行了监测。结果表明,该技术不仅可以用于新型树脂固化工艺制度的确定,也可用于复合材料固化工艺过程的在线监测。     

光纤传感器监测复合材料热压釜固化实验研究

利用最新发展的光纤传感技术可以对材料内部的固化情况进行全面有效的监测,例如,监测固化温度,粘滞度、孔隙率、压缩进程等.同时,基于监测信号实时调整工艺过程,就可以保证产品的质量.本文给出利用光纤传感器监测复合材料热压釜固化进程中粘度变化的实验结果,井对影响传感器工作的因素进行了分析.     

单根光纤光栅监测复合材料固化工艺过程多目标参量技术的研究

采用单根布拉格光纤光栅传感器实现了对复合材料工艺过程不同阶段、不同目标的监测。在成型阶段监测树脂的温度(粘度)发展历程；在施加成型压力时监测树脂内部压力的变化；在固化与降温阶段监测复合材料层板内部的应力变化。试验结果表明，利用-根布拉格光纤光栅传感器同时实现对复合材料固化工艺全过程的主要控制参量的监测是完全可行的。     

光纤光栅监测缠绕复合材料与铝板界面的固化应变

树脂基复合材料经常与金属材料固化在一起使用。用缠绕方法制备了复合材料单向板, 将光纤布拉格光栅(FBG) 埋入复合材料与铝板之间, 监测两种不同的材料在固化过程中界面的性质, 并与复合材料内部的监测结果相比较。监测结果表明, 光纤布拉格光栅准确地监测到了复合材料固化过程的温度历程, 复合材料内部、铝板和复合材料的界面在固化过程中和固化后应变存在着明显的差异。光纤光栅传感器为两种不同材料之间的固化监测提供了工具, 对界面性质的分析提供了新方法。      

用光纤进行树脂基复合材料的成型过程监测

研究了用光纤对碳纤维环氧树脂复合材料成型监测的方法和系统。通过测量复合材料成型过程中树脂折射率的变化来反映树脂的粘度变化和固化过程。     

光纤布拉格光栅传感器监测环氧树脂固化收缩研究

采用光纤布拉格光栅传感器对处于自由状态的热固性树脂在固化工艺过程中的温度和应变进行了实时在线监测,并且利用传感器的测量数据得到了固化后树脂在冷却阶段的热膨胀系数。结果表明:应用光纤布拉格光栅传感器能够实现从树脂凝胶点开始对固化过程中由于体积变化导致的树脂内部应变变化实时在线监测;传感器测得的固化后树脂在冷却阶段的热膨胀系数结果与热膨胀仪的测量结果相当;利用光纤布拉格光栅传感器测量热固性树脂的固化收缩具有较高的灵敏度和可靠性。     

滑坡崩塌岩体推力监测用分布式OTDR技术

提出了一种用圆形弹膜片和微弯调制机构进行应力传感,用光时域反射探测(OTDR)技术进行测量的分布式光纤应力传感方法。全面阐述了单模光纤微弯应力传感原理及应力传感器的动态范围与分布个数的关系。提出了一种不需要双光路信号就减小了光源波动及环境因素对测量的影响的解调应力方法。建立起了对岩体推力进行监测的试验系统,野外试验表明该传感器具有高灵敏度、高空间分辨率、工程实用性好的特点。     

Experimental Study of Monitoring and Controlling of Composite Cure Process in Autoclave Featured with Fiber Optic Sensor

With the aid of the latest fiber optic sensing technology, parameters in the cure process of therosetting resin-matrix composite, such as temperature, viscosity, void and residual stress, can be monitored entirely and efficiently. In this paper, experiment results of viscosity measurement in composite cure process in autoclave using fiber optic sensors are presented. Based on the sensed information, a computer program is utilized to control the cure process. With this technology,the cure process becomes more apparent and controllable, which will greatly improve the cured products and reduce the cost.     

A Fiber Optic Ultrasonic System to Monitor the Cure of Epoxy

A fiber optic ultrasonic system is described which monitors the cure of an epoxy resin. Ultrasound is generated using a high-power optical fiber to deliver high-energy pulses of light to the prepared surface of an aluminum mold that contains the curing epoxy resin. The generated ultrasound is detected using a local fiber optic ultrasound sensor embedded in the curing epoxy resin. The system was used to measure the ultrasonic signal velocity and ultrasonic attenuation throughout the cure of a neat epoxy resin at room temperature. Similar measurements also were performed using a piezoelectric transducer for ultrasound generation and an embedded fiber optic sensor for detection, which provided verification of the results using the complete fiber optic system. The complete fiber optic system demonstrated adequate sensitivity throughout the entire cure to measure the ultrasonic signal velocity and ultrasonic attenuation.     

多模光纤传感器复合材料固化实时监测研究

设计了一种新型光纤传感器，提出通过测量光纤末端近场模斑谱监测光纤埋置周转树脂折射率的变化。     

基于PPP-BOTDA技术的PBL剪力键群应变测试研究

为研究混合结构PBL剪力键群各剪力键的剪力传递,在开孔板界面摩擦效应测试中引入了光纤传感测试技术。阐述了PPP-BOTDA (Pulse-PrePump Brillouin Optical Time Domain Analysis)技术的测量原理,根据多中间层的剪滞理论,建立了基体-光纤间的应变传递模型,推导了表贴式光纤的应变传递公式,基于4个四排PBL剪力键群试件的静载破坏试验,实现了对PBL剪力键开孔钢板及混凝土应变的空间分布式测量,并对分布式传感光纤的应变传递进行了敏感性分析。测试结果及分析表明:在仪器的空间分辨率一定时,传感光纤的粘贴宽度、光纤护套的厚度对应变传递影响显著,粘结层胶体的剪切模量对应变传递影响不甚明显;对比剪力键试验中应变片与分布式光纤的应变数据,试验采用的两种光纤均具有良好的应变测量精度,试验结果与理论敏感性分析较为一致;基于PPP-BOTDA的分布式光纤测试方法,克服了传统应变片测试中的不足,在既定的光纤铺设工艺下,适用于结构的大应变、高精度、分布式测量。     

Composite Optical Bend Loss Sensor for Pressure and Shear Measurement

A composite optical bend loss sensor for measuring 3-D forces has been developed. The sensor is composed of two optic fiber meshes which are embedded into a polydimethylsiloxane (PDMS) slab. The sensor consists of an array of optical fibers lying in perpendicular rows and columns sandwiched inside an elastomeric pad. A map of normal and shear stress is constructed based on observed macrobending through the intensity attenuation from physical deformation of two adjacent perpendicular fibers. Due to the new addition of the composite design and acrylic holder, the stability of the present sensor is found to be significantly better than our previously reported microfabricated optical bend loss sensor. In this paper, we will report the results of an optical bend loss simulation using the beam propagation method based on a series of images captured by a CCD camera on the fiber's bending curvatures. The result from the simulation will be compared with the results obtained from the experiment. Other results include vertical force and shear measurements at a single pressure point of the sensor. A force image algorithm is used to map the force distribution detected by the sensor. Here, we will present the results of six different shape patterns and two force magnitudes on each shape using a neural network system. We will also present a radio frequency sensor module, which we developed for the composite optical bend loss sensor for remote sensing.     

Improving the precision of multimode optical fiber attenuationmeasurements/

To improve the precision of attenuation measurements for multimode optical fibers, the different measurement errors are analyzed and an error equation is established. This is used to quantify total error by inserting relevant parameters taken from a recent Chinese nationwide interlaboratory comparison of multimode optical fiber attenuation measurements. It is suggested that the measurement error of the attenuation of a multimode optical fiber be expressed in both the error for the total loss of the entire length of the fiber, and the error of the loss per unit length, rather than the usual way of only expressing it per unit length