PERFORMANCE OF STEEL MICRO FIBER REINFORCED MORTAR MIXTURES CONTAINING PLAIN,BINARY AND TERNARY CEMENTITIOUS SYSTEMS

Steel micro fibers provide strengthening,toughening and durability improve-ment mechanisms in cementitious composites.However,there is not much data in the literature regarding how the extent of their effectiveness changes depend-ing on the type of matrix being reinforced.For clarifying this point,the influ-ence of a constant volumetric ratio(1%)of 6 mm long steel micro fibers on the performance of 5 mortar mixtures was investigated and were prepared using plain,binary and ternary cementitious systems.A total of 10 mixtures were cast.The mineral admixtures used in the study include silica fume(SF),metakaolin(MK)and a Class C fly ash(FA).While the replacement levels of SF and MK were 10%by weight of the total mass of the binder,this ratio was chosen as 30%for FA.In addition to the behavior of the mixtures under compressive,flexural and impact loads,abrasion,water absorption,chloride ion penetration,freez-ing-thawing resistance and drying shrinkage characteristics of the mixtures were determined.Test results indicate that generally the refinement in the pore struc-ture of the matrix provided by mineral admixtures and the increase in resistance against growth and coalescence of micro-cracks provided by fibers produce a syn-ergistic effect and improve the investigated performances of the mixtures.

Correlation of Microstructure of Leaf Sheath Epidermis and Nutrient Composition of Palm Plants with the Damage Degree of Red Palm Fiber Elephant

[ Objective] Correlation of microstructure of leaf sheath epidermis and nutrient composition of palm plants with the damage degree of red palm fiber elephant in four kinds of plants in Nanning were analyzed in order to control the occurrence and damage of this insect in Nanning. [Method] Taken 4 kinds of Palmae plants in Nanning including Ravenea fivulafis, Washingtonia filifera, Phoenix canafiensis, Roystonea regia （HBK.）O. F. Cook as materials, damage situation of the red palm fiber elephant was investigated, microstructure of leaf sheath epidermis and nutrient composition of palm plants were analyzed and determined. [ Result] The results showed that there was direct correlation between the microstructure of leaf sheath epidermis and nutrient composition with the physical resistance of palm plant against red palm fiber elephant. The extend of damage from red palm fiber elephant had negatively relation with the thickness of corneum and leaf epidermis. The damage degree caused by red palm fiber elephant increased with the content of crude protein, crude ash and nitrogen free extract increasing, also increased with the content of rude fiber decreasing. [Condusion] The damage degree of red palm fiber elephant had a relationship with microstructure of leaf sheath epidermis and nutrient composition of palm plants.

Spectra of spontaneous Raman scattering in taper-drawn micro/nano-fibers

We study the spontaneous Raman scattering （RS） in taper-drawn micro/nano-fibers （MNFs） by employing the photon counting technique. The spectra of RS in five MNFs, which are fabricated by using different heating flames （hydrogen flame or butane flame） and with different diameters, are measured within a frequency shift range of 1435 cm- 1_3200 cm- 1. From the measured spectra, we observe the RS peaks originated from silica and a unique RS peak with a frequency shift of - 2905 cm-1 （- 87.2 THz）. Unlike the former ones, the latter one is not observable in conventional optical fibers. Furthermore, the unique peak becomes obvious and starts to rapidly increase with the decrease of the diameter of MNFs when the diameter is smaller than 2 μm, and the intensity of the unique peak significantly depends on the heating flame used in the fabricating process. Our investigation is useful for the entanglement generation or optical sensing using taper-drawn MNFs.

Research on Infrared Emissivity and Laser Reflectivity of Sn_(1−x)Er_(x)O_(2)Micro/Nanofibers Based on First-Principles

Sn_(1−x)Er_(x)O_(2)(x=0%,8%,16%,24%)micro/nanofibers were prepared by electrospinning combined with heat treatment using erbium nitrate,stannous chloride and polyvinylpyrrolidone(PVP)as raw materials.The target products were characterized by thermogravimetric analyzer,X-ray diffrotometer,fourier transform infrared spectrometer,scanning electron microscope,spectrophotometer and infrared emissivity tester,and the effects of Er^(3+)doping on its infrared and laser emissivity were studied.At the same time,the Sn_(1−x)Er_(x)O_(2)(x=0%,16%)doping models were constructed based on the first principles of density functional theory,and the related optoelectronic properties such as their energy band structure,density of states,reflectivity and dielectric constant were analyzed,and further explained the mechanism of Er^(3+)doping on SnO_(2)infrared emissivity and laser absorption from the point of electronic structure.The results showed that after calcination at 600℃,single rutile type SnO_(2)was formed,and the crystal structure was not changed by doping Er^(3+).The calcined products showed good fiber morphology,and the average fiber diameter was 402 nm.The infrared emissivity and resistivity of the samples both decreased first and then increased with the increase of Er^(3+)doping amount.When x=16%,the infrared emis-sivity of the sample was at least 0.71;and Er^(3+)doping can effectively reduce the reflectivity of SnO_(2)at 1.06μm and 1.55μm,when x=16%,its reflectivity at 1.06μm and 1.55μm are 50.5%and 40%,respectively,when x=24%,the reflectivity at 1.06μm and 1.55μm wavelengths are 47.3%and 42.1%,respectively.At the same time,the change of carrier concentration and electron transition before and after Er^(3+)doping were described by first-principle calculation,and the regulation mechanism of infrared emissivity and laser reflectivity was explained.This study provides a certain experimental and theoretical basis for the development of a single-type,light-weight and easily prepared infrared and laser compatible-stealth material.

Electromagnetism and Absorptivity of the Modified Micro-coiled Chiral Carbon Fibers

Micro-coiled chiral carbon fibers are modified by nano-Ni. X-ray diffraction （XRD） and scanning electron microscopy （SEM） are used to compare the composition and morphology of the unmodified and the modified fibers. The results show that electromagnetism parameters of the modified are different from those of the unmodified. After modification by nano-Ni, the micro-coiled chiral carbon fibers have decreased permittivity and electrical loss. The permeability and magnetic loss of the modified carbon fibers become larger than those of the unmodified ones. Moreover, the modification of unmodified chiral carbon fibers into the modified is much like changing hollow electric windings into those with magnetic cores inside. The modifier intensifies the cross polarization of the chiral carbon fibers and makes the permittivity and the permeability get closer to each other which improves the matching performance and enhances absorbability of coatings. In the range of 6-18 GHz, the reflectivity of the coating is 6-8dB and the bandwidth is 12 GHz. The area density of the coating is below 3 kg/m^2.

Capillary Micro-Flow Through a Fiber Bundle(Ⅰ)

The present work considered the capillary micro-flow through a fiber bundle.The resin heights in the fiber bundle as a function of time were used to determine the experimental values of capillary pressure and the permeability by the nonlinear regression fitting method.The fitting curves showed a good agreement with experiments.However,these values of capillary pressure from short-time experiments were much lower than the theoretical results from the Yang-Laplace Equation.More accurate capillary pressure was predicted from the presented long-run experiment.

Characteristics and Formation Mechanism for Stainless Steel Fiber with Periodic Micro-fins

Metal fibers have been widely used in many industrial applications due to their unique advantages. In certain applications, such as catalyst supports or orthopedic implants, a rough surface or tiny outshoots on the surface of metal fibers to increase surface area are needed. However, it has not been concerned about the surface morphologies of metal fiber in the current research of metal fiber manufacturing. In this paper, a special multi-tooth tool composed of a row of triangular tiny teeth is designed. The entire cutting layer of multi-tooth tool bifurcates into several thin cutting layers due to tiny teeth involved in cutting. As a result, several stainless steel fibers with periodic micro-fins are produced simultaneously. Morphology of periodic micro-fins is found to be diverse and can be classified into three categories： unilateral plane, unilateral tapering and bilateral. There are two forming mechanisms for the micro-fins. One is that periodic burrs remained on the free side of cutting layer of a tiny tooth create micro-fins of stainless steel fiber produced by the next neighboring tiny tooth; the other is that the connections between two fibers stuck together come to be micro-fins if the two fibers are finally detached. Influence of cutting conditions on formation of micro-fins is investigated. Experimental results show that cutting depth has no significant effect on micro-fin formation, high cutting speed is conducive to micro-fin formation, and feed should be between 0.12 mm/r and 0.2 mm/r to reliably obtain stainless steel fiber with micro-fins. This research presents a new pattern of stainless steel fiber characterized by periodic micro-fins formed on the edge of fiber and its manufacturing method.

Capillary Micro-flow Through a Fiber Bundle(Part 2)

A numerical model was proposed to simulate the capillary micro-flow through a fiber bundle. The capillary pressure was predicted by the Young-Laplace equation and the corresponding optimal values of permeability were found by a trial-and-error method. The empirical Kozeny constants which are dependent on fiber volume fraction were recormnended for the prediction of permeability.

Micro Model of Carbon Fiber/Cyanate Ester Composites and Analysis of Machining Damage Mechanism

Machining damage occurs on the surface of carbon fiber reinforced polymer (CFRP) composites during processing. In the current simulation model of CFRP, the initial defects on the carbon fiber and the periodic random distribution of the reinforcement phase in the matrix are not considered in detail, which makes the characteristics of the cutting model significantly different from the actual processing conditions. In this paper, a novel three-phase model of carbon fiber/cyanate ester composites is proposed to simulate the machining damage of the composites. The periodic random distribution of the carbon fiber reinforced phase in the matrix was realized using a double perturbation algorithm. To achieve the stochastic distribution of the strength of a single carbon fiber, a novel method that combines the Weibull intensity distribution theory with the Monte Carlo method is presented. The mechanical properties of the cyanate matrix were characterized by fitting the stress-strain curves, and the cohesive zone model was employed to simulate the interface. Based on the model, the machining damage mechanism of the composites was revealed using finite element simulations and by conducting a theoretical analysis. Furthermore, the milling surfaces of the composites were observed using a scanning electron microscope, to verify the accuracy of the simulation results. In this study, the simulations and theoretical analysis of the carbon fiber/cyanate ester composite processing were carried out based on a novel three-phase model, which revealed the material failure and machining damage mechanism more accurately.

Mechanical Properties of Submicron Glass Fiber Reinforced Vinyl Ester Composite

Vinyl ester (VE) resin inherently has intrinsic brittleness due to its high cross-link density. To improve mechanical performance, micro/nano fillers are widely used to modify this matrix. In present study, glass fiber in submicron scale at low contents was added into VE to prepare submicron composite (sMC). The impact resistance of un-notched sMC degraded with the increase of sGF content while that of notched-sMC remained the unchanged. Flexural properties of sMCs also were the same with that of neat resin. The results of Dynamic mechanical analysis (DMA) test showed the slight increase of storage modulus and the decrease of tan delta value in the case of sMC compared to those of un-filled matrix. However, the Mode I fracture toughness of sMC improved up to 26% and 61% corresponding to 0.3 and 0.6 wt% glass fiber used. The compact tension sample test suggests that there is the delay of crack propagation under tensile cyclic load in resin reinforced by submicron glass fiber. The number of failure cycle enlarged proportionally with the increment of sGF content in matrix.

Flexible Optical Waveguide Bent Loss Attenuation Effects Analysis and Modeling Application to an Intrinsic Optical Fiber Temperature Sensor

The temperature dependence of the bending loss light energy in multimode optical fibers is reported and analyzed. The work described in this paper aims to extend an initial previous analysis concerning planar optical waveguides, light energy loss, to circular optical waveguides. The paper also presents à novel intrinsic fiber optic sensing device base on this study allowing to measure temperatures parameters. The simulation results are validated theoretically in the case of silica/silicone optical fiber. A comparison is done between results obtained with an optical fiber and the results obtained from the previous curved optical planar waveguide study. It is showed that the bending losses and the temperature measurement range depend on the curvature radius of an optical fiber or waveguide and the kind of the optical waveguide on which the sensing process is implemented.

Micro-yield behaviors of Al_2O_3-SiO_(2(sf))/Al-Si metal matrix composites

Effects of the volume fraction and the size of crystallized alumina silicate short fibers as well as heat treatment processes on micro-yield strength(MYS) of Al2O3-SiO2(sf)/Al-Si metal matrix composite(MMC) that was fabricated by squeezing cast, were investigated by using continuous loading method on an Instron 5569 tester with a special extensometer with an accuracy of 10?7. The results show that MYS of MMC decreases with the increase of volume fraction and length of the alumina silicate short fibers in the metal matrix composite, respectively. MYS of quenched Al2O3-SiO2(sf)/Al-Si MMC is the lowest, MYS of the MMC through peak-aging treatment is higher than that through other heat treatment methods. And before the peak-aging, MYS of MMC aging treated gradually increases with the increase of the aging time. Aging treatment after solution treatment is a preferred way that enhances micro and macro-yield strength of Al2O3-SiO2(sf)/Al-Si MMC.

Triple and Double Photons Absorption Process and Down-Conversion Laser Emitting Investigation of Er-Ion Doped Microsphere

We report a readily and cheap method to build taper optical fiber-Er3+ doped microsphere platform to investigate upconversion fluorescence emission and down-conversion laser oscillation with low threshold pump power. We demonstrate to dope Er3+ into silica microsphere surface by dipping a single-taper optical fiber into a certain concentration of erbium nitrate solution (Er(NO3)) , then dry it and use the electrical-arc of the optical fiber splicer to melt the tip of taper fiber to form the Er3+-doped silica microsphere due to surface tension induced. We also present a HF acid etching setup to fabricate low loss biconical optical taper fibers. We demonstrate the Er3+ doped silica microsphere triple photons and dual photons absorption process of up-conversion fluorescence emission and down-conversion laser oscillation spectra by using the optical tapered fiber to couple 976 nm/1534 nm pump light source.

High Power Fiber Bundle Array Coupled LDA Module

An optical fiber bundle array coupling module with high output power is presented in this paper. The device integrated the coupling technique of the high power laser diode array (LDA) and the micro-ball lenses fiber array. This module can efficiently couple the output laser of the LDA into 19 fibers array with micro-ball lens end-surface. The difference of the couple efficiency between the flat-end fiber and micro-ball-end fiber is discussed. The micro-ball lenses fiber array made of 19 fibers have the same fiber core diameter of 200 m, and then the end-surfaces of 19 fibers are fused to 19 micro-ball lenses. The micro-ball lenses fiber array are fixed precisely in the neighborhood on the V-grooves, and the fiber array has the same arrange period with the semiconductor laser units of LDA. This configuration of micro-ball lens fiber array can greatly reduce the divergence of the laser beam from all directions, and a very efficient laser beam homogenizer and shaper are obtained. Finally, high output power of 30.1 W of the fiber coupled LDA is achieved, and the maximal coupling efficiency is >83% with the numeral aperture (NA) of 0.16.

Temperature measurement based on radialization power for micro-hotplate

A novel method to measure the temperature on the surface of micro-hotplate was presented. The tiny fiber probe and the optical power meter were employed to measure the sample radialization power. By means of comparing the relationship between the radialization power and the temperature, sample surface temperature can be discerned accurately. Such an approach has provided more accuracy than traditional temperature measurements. The experimental result based on this method is quite similar to that of simulation by the finite element analysis (FEA) software of Ansys in theory. This measurement is very useful for measuring temperature for these micro samples prone to be untouchable.

Axial Micro-Strain Sensor Based on FM-FBG via Dual-Mode ML-FMF in Sensor Networks

An in-fiber axial micro-strain sensor based on a Few Mode Fiber Bragg Grating (FM-FBG) is proposed and experimentally characterized. This FM-FBG is in inscribed in a multi-layer few-mode fiber (ML-FMF), and could acquire the change of the axial strain along fibers, which depends on the transmission dips. On account of the distinct dual-mode property, a good stability of this sensor is realized. The two transmission dips could have the different sensing behaviors. Both the propagation characteristics and operation principle of such a sensor are demonstrated in detail. High sensitivity of the FM-FBG, ~4 pm/με and ~4.5 pm/με within the range of 0 με - 1456 με, is experimentally achieved. FM-FBGs could be easily scattered along one fiber. So this sensor may have a great potential of being used in sensor networks.

Out of Plane Thermal Conductivity of Carbon Fiber Reinforced Composite Filled with Diamond Powder

Highly conductive fillers have a strong influence on improving the poor out of plane thermal conductivity of carbon fiber reinforced composites. The objective of this study has been to investigate the role of the diamond powder (DP) in enhancing the out-of-plane thermal conductivity of the woven composites. Samples of the standard modulus T300 carbon fiber composite with 44% and 55% fiber volume fraction and the high modulus YS90A carbon fiber composite with 50% volume fraction were fabricated with their matrices comprising of neat epoxy and different loading of diamond powder within epoxy resin. Steady state thermal conductivity measurements were carried out and it was found from the measurements that the out of plane thermal conductivity of the standard modulus composite increased by a factor of 2.3 with 14% volume fraction of diamond powder in the composite while the out of plane thermal conductivity of the high modulus composite increased by a factor of 2.8 with 12% volume fraction of diamond powder in the composite. Finite Element Modeling (FEM) with the incorporation of microstructural characteristics is presented and good consistency between the measurements and FEM results were observed.

玄武岩纤维对混凝土抗冻性能的影响

为研究玄武岩纤维掺量对混凝土抗冻性能的影响及作用机理,开展了快速冻融试验和微观孔隙试验,研究了4种不同玄武岩纤维体积掺量(0、0.1%、0.2%、0.3%)混凝土冻融循环过程中的外观、质量损失率、相对动弹性模量、抗压强度、抗折强度、冲击弹性波波速损失率及气泡特征参数的变化规律,并通过灰熵分析法对玄武岩纤维改善混凝土性能的微观机理进行了研究。结果表明:混凝土各项性能随着冻融循环次数的增加而逐渐降低;掺加玄武岩纤维能够提高混凝土抗冻性能且存在最优掺量;玄武岩纤维混凝土宏观性能的改变与气孔比表面积、含气量、弦长>200 nm气孔频率等微观孔隙参数之间呈一定的相关性;玄武岩纤维掺量为0.2%时对混凝土抗冻性能的改善效果最佳。

UHPM改性火龙果皮膳食纤维工艺优化及其结构表征研究

研究火龙果皮膳食纤维超高压微射流(UHPM)改性工艺优化,并对改性后的膳食纤维结构进行分析。以火龙果皮为原料,采用UHPM进行处理,研究UHPM压力、液料比和处理次数对可溶性膳食纤维(SDF)含量的影响,通过响应面试验优化UHPM改性工艺条件,并对UHPM改性前后的火龙果皮膳食纤维显微结构、扫描电镜照片、红外光谱特性进行分析。结果表明:优化的火龙果皮膳食纤维UHPM改性工艺为压力165 MPa、液料比20∶1 g/mL、处理4次。该条件下火龙果皮膳食纤维的SDF含量为29.12%。同未经UHPM处理的样品相比,165 MPa处理的火龙果皮膳食纤维,细胞被充分破碎,膳食纤维的氢键破坏。表明UHPM是改性火龙果皮膳食纤维适宜的方法。

导电微纳纤维复合纱的制备及其气敏特性

为开发高质量的气敏传感器,利用水浴静电纺丝法制备以涤纶(PET)为芯纱,聚酰胺6(PA6)纳米纤维为包覆层的微纳纤维复合纱(MNY),基于原位聚合方法对MNY进行连续导电处理,制备微纳米纤维复合纱/聚苯胺(MNY/PANI)复合导电纱,以此作为气敏元件,同时将相同参数下制备的PET/PANI复合导电纱也作为气敏元件进行对照,探究不同结构纱线之间气敏效果的差异。研究结果表明:MNY具备良好的皮芯结构,经导电处理后MNY表面均匀分布了聚苯胺颗粒,MNY/PANI的电导率最高可达7.53 S/cm;相比于PET/PANI气敏元件,MNY/PANI气敏元件因其纳米结构的高比表面积对NH 3的灵敏度更高,能表现出更好的响应-恢复效果,重复性和稳定性更好,已初步具备了作为优良气敏元件的条件。