Method for embedding optical fibers in an aluminum matrix by ultrasonic consolidation

The overall aim of the research, part of which is outlined in this paper, was to utilize the ultrasonic consolidation (UC) process for the fabrication of smart metal structures, capable of measuring an external stimulus and responding to this stimulus by adapting its structure accordingly through embedding both active and passive functional elements. This paper presents a fundamental study of embedding methods for the fabrication of optical fibers embedded within aluminum structures. The methods considered in this paper produced embedded optical fiber specimens in which large amounts of plastic flow were observed within the matrix. The matrix material deformed around the fibers, resulting in fully embedded optical fibers capable of transmitting a bright light source and without damaging the fibers. Based on light responses, a general process window was drawn to show the range at which optical fibers can be embedded within aluminum structures using the UC process. The outcomes lay down initial investigative principles for the further development of the technology for embedding or cladding of optical fiber sensors, such as fiber Bragg grating devices, within or on metal structures: for example, the cladding of large free-form metal structures or smart "skinned" metal foam or metal honeycomb structures.     

Future Trends and Recent Developments of Fabrication Technology for Advanced Metal Matrix Composites

Future trends and recent developments of reinforcing materials and fabrication processing for advanced metal matrix composites are discussed in this paper. A national R & D project is currently underway to improve the oxidation resistance and heat resistance to 1773 K of continuous ceramics Si-Ti-C-O fibers (Tyranno fiber) and SiC(PC)) fibers (Nicalon fiber) by electron beam irradiation curing techniques. Meanwhile, over the past seven years from 1981, a large national R & D project on MMC has been performed in Japan. Overviews of both projects are reported including the major fabrication methods (squeeze casting, plasma spraying and powder metallurgy) of advanced MMCs. The status and future trends of these methods are considered.     

连续纤维增强SiC复合材料制备工艺与性能研究进展

综述了国内外碳纤维与碳化硅纤维增强碳化硅复合材料的制备工艺与性能的研究进展,并介绍了其氧化性能及防护措施.认为连续纤维增强SiC复合材料的制备工艺复杂,成本较高,生产周期长,但是如果采用连接技术制备成陶瓷/金属复合构件使用,既有利于降低成本,又能够扩大该先进陶瓷基复合材料的应用范围.目前,国内对连续纤维增强的SiC复合材料与金属(如高温合金等)的连接技术研究较少.     

短碳纤维／银基复合材料的研制及性能研究

本文研究了用粉末冶金法制备短切碳纤维／银基复合材料，对复合材料进行了物理、机械性能测试并应用于电触点进行了电寿命试验。结果表明，不同的制造工艺对复合材料的性能影响很大。通过对碳纤维表面预处理、造反正确的制造工艺可以制得性能优于银／石墨系列的短碳纤维／银基复合材料。     

Warmfeste Faserverbundwerkstoffe mit Metallmatrix

Metalmatrix Composites for High Temperatures . Developmental features are shown of fiber reinforced metal matrix composites with high-temperature strength and their problems of application in gas turbine blades with the most severe mechanical, chemical and thermal service conditions. Stability and strength at high temperatures are discussed in general as well as fabrication problems and properties of composites with separately produced fibers and ?in-situ”? composites out of directionally solidified eutectics. Advantages and disadvantages of the different approaches are compared.     

Optical fiber sensor based on oblique angle deposition

The technique of oblique angle deposition has been extended to the fabrication of nanostructured metal coatings on the tips of standard silica optical fibers by thermal evaporation. The coatings are initiated as metal island films, which grow into extended rodlike structures as the deposition continues. The nanorod coatings demonstrate excellent surface-enhanced Raman scattering performance with variability of less than 10% as shown by direct measurements off the fiber tip with thiophenol as a test analyte. However, in the remote sensing configuration, the nanorod structures perform no better than thin metal island films. This appears to be mainly due to reduced transmission when nanorod lengths exceed ~100 nm. Moreover, the variability of remote measurements is increased to 18%. This is believed to be due to variations in coupling efficiency.     

FRM用先进陶瓷纤维及其拉伸强度

陶瓷,其耐热性、耐腐蚀性、功能性等引起人们重视,作为一种新材料而得到开发,其有用性得到了公认。所谓新材料,或明显提高原料纯度,或使其形状极端微细化、微粉化或者薄膜化,或使原料组合、制成合金,从而使材料性能得到空前的发挥。碳化硅(SiC)、硼(B)、氧化铝(Al₂O₃)等陶瓷也可使其形状变成又细又长的纤维状,从而使拉伸强度提高,使陶瓷的使用变得容易起来。本稿将就最近开发的轻质高强陶瓷纤维的性能加以介绍。      

Fabrication method of ultra-small gradient-index fiber probe

Fabrication method and device of ultra-small gradient-index(GRIN) fiber probe were investigated in order to explore the development of ultra-small probes for optical coherence tomography(OCT) imaging.The beamexpanding effect of no-core fiber(NCF) and the focusing properties of the GRIN fiber lens were analyzed based on the model of GRIN fiber probe consisting of single-mode fiber(SMF),NCF and GRIN fiber lens.A stereo microscope based system was developed to fabricate the GRIN fiber probe.A fiber fusion splicer and an ultrasonic cleaver were used to weld and cut the fiber respectively.A confocal microscopy was used to measure the dimensions of probe components.The results show that the sizes of probe components developed are at the level of millimeter.Therefore,the proposed experimental system meets the fabrication requirements of an ultra-small self-focusing GRIN fiber probe.This shows that this fabrication device and method can be employed in the fabrication of ultrasmall self-focusing GRIN fiber probe and applied in the study of miniaturized optical probes and OCT systems.     

Fabrication and modeling of uniform-waist single-mode tapered optical fiber sensors

We report the fabrication and modeling of single-mode tapered optical fiber sensors. The fabrication technique consist of stretching a section of fiber with an oscillating flame torch. Such a process allows controllable fabrication of lossless tapered fibers with a uniform waist. The sensor transmittance is modeled with a simple ray optics approach. In the model, all the taper parameters are taken into account. Our results indicate that sensor sensitivity can be adjusted with the taper waist diameter. As an example a gold-coated tapered fiber is theoretically and experimentally analyzed.     

High mechanical performance SiC/SiC composites by NITE process with tailoring of appropriate fabrication temperature to fiber volume fraction

Unidirectional SiC/SiC composites are prepared by nano-powder infiltration and transient eutectic-phase (NITE) process, using pyrolytic carbon (PyC)-coated Tyranno-SA SiC fibers as reinforcement and SiC nano-powder with sintering additives for matrix formation. The effects of two kinds of fiber volume fraction incorporating fabrication temperature were characterized on densification, microstructure and mechanical properties. Densification of the composites with low fiber volume fraction (appropriately 30 vol%) was developed even at lower fabrication temperature of 1800 °C, and then saturated at 3rd stage of matrix densification corresponding to classic liquid phase sintering. Hence, densification of the composites with high volume fraction (above 50 vol%) became restricted because the many fibers retarded the infiltration of SiC nano-powder at lower fabrication temperature of 1800 °C. When fabrication temperature increased by 1900 °C, densification of the composites was effectively enhanced in the intra-fiber-bundles and simultaneously the interaction between PyC interface and matrix was strengthened. SEM observation on the fracture surface revealed that fiber pull-out length was accordingly changed with fabrication temperature as well as fiber volume fraction, which dominated tensile fracture behaviors. Through NITE process, SiC/SiC composites with two fracture types were successfully developed by tailoring of appropriate fabrication temperature to fiber volume fraction as follows: (1) high ductility type and (2) high strength type.     

A Novel Fiber-Optic Tapered Long-Period Grating Sensor for Pressure Monitoring

The method and the required installations for fabricating tapered long-period fiber gratings can be simpler than that of standard fiber Bragg gratings, and the fabrication process is faster. To our knowledge, the tapered long-period fiber grating pressure sensor is presented here for the first time. In this paper, the fabrication method for tapered long-period fiber gratings, the sensing principle, the sensor structure, the measurement setup, and the preliminary results are presented and discussed. The pressure sensitivity of the sensor is as high as 5.1 pm/bar.     

基于光束扫描方法制作取样光栅的实验研究

报道了一种基于光束扫描方法采用普通均匀相位模板和连续的 2 4 4nm倍频氩离子激光器 ,制作波长间隔为 0 .8nm和 1.6nm取样光栅的新技术 ,并对得到的实验结果进行了分析。研制的取样光栅波长间隔均匀 ,具有良好的谱特性。采用的方法操作简单、灵活 ,可方便地制作不同类型的取样光栅。     

Corrosion behaviour of aluminium-based metal matrix composites

The corrosion characteristics, in 3.5 wt% NaCl solution, of aluminium alloy composites containing a range of reinforcements have been investigated using potentiostatic measurements and simple immersion tests. Complementary microstructural studies carried out on corroded surfaces and sections through corroded material have identified a number of preferential corrosion sites; these include the fiber/matrix interface, especially where it contains chemical reaction products resulting from composite fabrication, as well as second phases and pores in the metal matrix. The effect on corrosion behaviour of the different reinforcements, with particular reference to their chemistry and geometry, is discussed, as is the influence of composite manufacturing route.     

Semiellipsoid microlens fabrication method using UV proximity printing

We present a new semiellipsoid microlens fabrication method that controls the printing gap in the UV lithography process without thermal reflow. The UV proximity printing method can precisely control the curvature radius ratio of the semiellipsoid microlens in the fabrication process. The proposed fabrication method facilitates mass production to achieve a high-yield and high-coupling semiellipsoid microlens that is suitable to be used in commercial fiber transmission systems. A semiellipsoid microlens can be tipped on a single-mode fiber end to improve power coupling efficiency from laser diodes. The semiellipsoid microlens allows increasing the fiber spot size and numerical aperture. It is very important to control the geometric parameters in the assembly procedure to increase the optical coupling efficiency between the laser diode and single-mode fiber. Wide misalignment tolerance, low loss, and low manufacturing cost could be achieved by the proposed fabrication method. The theoretical model is first developed to predict the optical coupling efficiency for various microstructure geometries of semiellipsoid microlens and assembly parameters in this study. Then, the Taguchi method is applied to obtain the optimal geometric parameters setting. The results show that optical coupling efficiency could be significantly improved by using the optimal geometric parameters setting.     

Miniature fiber-optic pressure sensor with a polymer diaphragm

The fabrication and experimental investigation of a miniature optical fiber pressure sensor for biomedical and industrial applications are described. The sensor measures only 125 microm in diameter. The essential element is a thin polymer diaphragm that is positioned inside the hollow end of an optical fiber. The cavity at the fiber end is made by a simple and effective micromachining process based on wet etching in diluted HF acid. Thus a Fabry-Perot interferometer is formed between the inner fiber-cavity interface and the diaphragm. The fabrication technique is described in detail. Different sensor prototypes were fabricated upon 125 microm-diameter optical fiber that demonstrated pressure ranges from 0 to 40 and from 0 to 1200 kPa. A resolution of less than 10 Pa was demonstrated in practice. The fabrication technique presented facilitates production of simple and low-cost disposable pressure sensors by use of materials with that ensure the required biocompatibility.     

树脂基纤维复合材料的热残余应力数值分析

以环氧树脂R368-1/硼纤维复合材料为研究对象,采用柱体单胞结构,建立了三维有限元分析模型。考虑试样加工制备过程和常温使用时的温度差,对残余应力分布特点和应力水平进行了讨论,给出了应力分布云图和应力沿径向的分布规律。进一步考察了纤维体积分数、温度差和附加界面层对残余应力分布的影响,结果表明,基体主要受拉伸应力作用,纤维主要受压缩应力作用,纤维体积分数增加和附加界面层有助于改善复合材料中残余应力的分布,试样制备温度的升高对纤维中应力的增加具有较大影响。     

Anisotropic Effective Thermal Conductivity Measurement of Various Kinds of Metal Fiber Materials

Recently, metal fiber materials were made by laminating metal fibers with a diameter of about 30 μm to 300 μm. Since the almost metal fibers were oriented in the horizontal direction (the major axis of the fiber), these metal fiber materials are estimated to be anisotropic with an effective thermal conductivity. However, there is little quantitative data on the anisotropic effective thermal conductivity of the various kinds of metal fiber materials. The purpose of this study is to investigate the anisotropic effective thermal conductivity of various metal fiber materials experimentally and theoretically. In order to measure the horizontal and vertical effective thermal conductivities of these metal fiber materials, new measurement devices were developed. As a result, it is found that the anisotropic effective thermal conductivity of the various metal fiber materials was confirmed, and the horizontal and vertical effective thermal conductivities of these metal fiber materials depend on the bulk density or porosity, Young’s modulus, the fiber length, and fiber diameter. And a dimensionless correlation equation for predicting the vertical and horizontal effective thermal conductivities of the various kinds of metal fiber materials was derived in terms of various dimensionless parameters.     

Polyacrylonitrile-based carbonized fibers and metal-carbonized fiber nanocomposites for thermal transport

This work examines the fabrication and thermal analysis of metal-carbon composite fibers prepared via an electrospinning process. The metal-carbon composite fibers of silver, copper, gold, and nickel were prepared by electrospinning of a composite solution of polyacrylonitrile (PAN) and metal precursor followed by heat treatment in air, nitrogen to 1000 degrees C and in 6% H2, respectively. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy dispersive spectroscopy (EDS) and Scanning thermal microscopy (SThM) were applied to characterize the metal-carbon fibers. TEM analysis showed a relatively uniform, contact-free distribution of the nanoparticles on the surface of the carbon fibers with size range of 3 nm-10 nm. Thermal analysis data showed an enhancement in the thermal conductivity of the nanomaterials when compared with the model PAN-based carbonized fibers. This was attributed to the incorporation of metal nanoparticles in the fiber matrix and on the surface.     

Fabrication of advanced fiber Bragg gratings by use of sequential writing with a continuous-wave ultraviolet laser source

We present a novel scheme based on sequential writing for fabrication of advanced fiber Bragg gratings. As opposed to earlier sequential methods this technique uses a cw UV laser source and allows for very precise control and repetitivity of the formation of the gratings. Furthermore it is possible to use high average irradiances without destroying the fiber, resulting in considerable reduction in fabrication time for complex gratings. The method has been applied to several test gratings, which proved its versatility and quality.     

纤维金属层板制备成形的研究现状及发展趋势

随着航空航天和汽车等结构领域对轻量化的要求越来越高,纤维金属层板作为一种新型混杂复合材料得到广泛的关注。综述了纤维金属层板的最新研究进展,主要对纤维金属层板进行了3种不同类型的分类,并对其在飞机和汽车上的应用做了分析,介绍了纤维金属层板制备成形的国内外研究现状,以及针对纤维增强树脂体系的不同而采用的纤维金属层板的2种成形制备工艺:层压固化制备工艺(包括滚弯成形、喷丸成形)和金属塑性成形工艺(冲压成形、充液成形等),最后对纤维金属层板的特性及其在未来航空航天和汽车制造上的生产应用进行了展望。