A review on machinability of carbon fiber reinforced polymer(CFRP)and glass fiber reinforced polymer(GFRP)composite materials

Fiber reinforced polymer(FRP) composite materials are heterogeneous and anisotropic materials that do not exhibit plastic deformation. They have been used in a wide range of contemporary applications particularly in space and aviation,automotive,maritime and manufacturing of sports equipment. Carbon fiber reinforced polymer(CFRP) and glass fiber reinforced polymer(GFRP) composite materials,among other fiber reinforced materials,have been increasingly replacing conventional materials with their excellent strength and low specific weight properties. Their manufacturability in varying combinations with customized strength properties,also their high fatigue,toughness and high temperature wear and oxidation resistance capabilities render these materials an excellent choice in engineering applications.In the present review study,a literature survey was conducted on the machinability properties and related approaches for CFRP and GFRP composite materials. As in the machining of all anisotropic and heterogeneous materials,failure mechanisms were also reported in the machining of CFRP and GFRP materials with both conventional and modern manufacturing methods and the results of these studies were obtained by use of variance analysis(ANOVA),artificial neural networks(ANN) model,fuzzy inference system(FIS),harmony search(HS) algorithm,genetic algorithm(GA),Taguchi's optimization technique,multi-criteria optimization,analytical modeling,stress analysis,finite elements method(FEM),data analysis,and linear regression technique. Failure mechanisms and surface quality is discussed with the help of optical and scanning electron microscopy,and profilometry. ANOVA,GA,FEM,etc. are used to analyze and generate predictive models.

Two-dimensional materials-decorated microfiber devices for pulse generation and shaping in fiber lasers

Two-dimensional（2D） materials have been regarded as a promising nonlinear optical medium for fabricating versatile optical and optoelectronic devices. Among the various photonic applications, the employment of 2D materials as nonlinear optical devices such as saturable absorbers for ultrashort pulse generation and shaping in ultrafast lasers is one of the most striking aspects in recent years. In this paper, we review the recent progress of 2D materials based pulse generation and soliton shaping in ultrafast fiber lasers, and particularly in the context of 2D materials-decorated microfiber photonic devices. The fabrication of 2D materials-decorated microfiber photonic devices, high performance mode-locked pulse generation, and the nonlinear soliton dynamics based on pulse shaping method are discussed. Finally, the challenges and the perspective of the 2D materials-based photonic devices as well as their applications are also discussed.

Evaluation of Fracture Resistance for Autopolymerizing Acrylic Resin Materials Reinforced with Glass Fiber Mesh, Metal Mesh and Metal Wire Materials: An in Vitro Study

Statement of problem: Many processes have been applied to improve the fracture resistance of acrylic resin dentures by reinforcing them. The maximum goal of any denture repair is to restore the main strength of the denture and to avoid further fracture. Purpose: This study investigated the ability of self-curing acrylic resin to be strength and deflection of repaired acrylic resin joints reinforced with various reinforcement materials to resist fracture. Material and methods: Transverse strength of polymethyl methacrylate acrylic resin reinforced with glass fiber mesh, metal mesh, and metal wire was evaluated with a 3-point load test on 40 intact specimens (n = 10 for control group) (n = 10 per each reinforcement material group). Fractured joint margins were rounded, a 4-mm gap was placed between them, and then they were repaired with autopolymerizing acrylic resin and retested. Results: Transverse strength for the polymethyl methacrylate acrylic resin samples has showed fracture at the side of sample rather than in the middle area of reinforcement materials and some other samples showed bending statue rather than fracture. Conclusion: Reinforcement with glass fiber mesh, metal mesh, and metal wire produced transverse strength in the side area of resin denture base material rather than in the middle of reinforcement area with bending samples rather than fracture response.

Influence of Some Plant Fibers on the Mechanical Performance of Composite Materials

This work focused on the search for biobased materials capable of being used in road techniques as soil inclusions, and on studying the influence of their incorporation on the characteristic parameters of pavement layers. To this end, pineapple, cyperus and imperata plant fibers, due to their endemic availability, were used as reinforcement on sourced materials, notably bar soil, lateritic gravel and silty sand. Complete identification and mechanical tests (Proctor and CBR) were carried out on materials in their natural state (soil) and on composite materials (soil + plant fibers) in the laboratory to determine their classification in road geotechnics, their compaction parameters and their mechanical behavior. Firstly, the various types of 2.5 cm long fibers were incorporated into the different types of soil at mass contents of 1% and 2%. This part of the study showed that the pineapple fiber composite incorporated into class A2 bar soil offered the best results, with a 38% gain in CBR index compared with the natural soil. Pineapple fibers incorporated at 1% in lateritic gravel raise the CBR value of the reinforced soil to 10% of the CBR value of the natural soil and to 7% for silty sand.

AN EXPERIMENTAL STUDY ON POST-BUCKLING BEHAVIOR OF SLENDER COLUMN WITH FIBER REINFORCED COMPOSITE MATERIAL

Equilibrium paths of post-buckling are measured for large slenderness column specimens made of the fiber reinforced composite material. The influence of the initial curvature is investigated experimentally and compared with the result of the initial post-buckling theory. Both the theoretical and experimental results reveal that the column with the initial curvature has stable post-buckling behaviors and is not sensitive to the imperfection in the form of initial curvature. The experimental results show that when the lateral buckling displacement is less than 20 percent of the column length, the experimental results agree with the results from the theory of initial post-buckling quite well, while they agree with the results from the large deflection theory in a quite large range.

Advanced Welding Technology for Highly Stressable Multi-Material Designs with Fiber-Reinforced Plastics and Metals

Organic sheets made out of fiber-reinforced thermoplastics are able to make a crucial contribution to increase the lightweight potential of a design. They show high specific strength- and stiffness properties, good damping characteristics and recycling capabilities, while being able to show a higher energy absorption capacity than comparable metal constructions. Nowadays, multi-material designs are an established way in the automotive industry to combine the benefits of metal and fiber-reinforced plastics. Currently used technologies for the joining of organic sheets and metals in large-scale production are mechanical joining technologies and adhesive technologies. Both techniques require large overlapping areas that are not required in the design of the part. Additionally, mechanical joining is usually combined with “fiber-destroying” pre-drilling and punching processes. This will disturb the force flux at the joining location by causing unwanted fiber- and inter-fiber failure and inducing critical notch stresses. Therefore, the multi-material design with fiber-reinforced thermoplastics and metals needs optimized joining techniques that don’t interrupt the force flux, so that higher loads can be induced and the full benefit of the FRP material can be used. This article focuses on the characterization of a new joining technology, based on the Cold Metal Transfer (CMT) welding process that allows joining of organic sheets and metals in a load path optimized way, with short cycle times. This is achieved by redirecting the fibers around the joining area by the insertion of a thin metal pin. The path of the fibers will be similar to paths of fibers inside structures found in nature, e.g. a knothole inside of a tree. As a result of the bionic fiber design of the joint, high joining strengths can be achieved. The increase of the joint strength compared to blind riveting was performed and proven with stainless steel and orthotropic reinforced composites in shear-tests based on the DIN EN ISO 14273. Every specimen joined with the new CMT Pin joining technology showed a higher strength than specimens joined with one blind rivet. Specimens joined with two or three pin rows show a higher strength than specimens joined with two blind rivets.

Two-dimensional MXene hollow fiber membrane for divalent ions exclusion from water

Two-dimensional material membranes with fast transport channels and versatile chemical functionality are promising for molecular separation.Herein,for the first time,we reported design and engineering of two-dimensional Ti_(3)C_(2)Tx MXene(called transition metal carbides and nitrides)membranes supported on asymmetric polymeric hollow fiber substrate for water desalination.The membrane morphology,physicochemical properties and ions exclusion performance were systematically investigated.The results demonstrated that surface hydrophilicity and electrostatic repulsion and size sieving effect of interlayer channels synergistically endowed the MXene hollow fiber membrane with fast water permeation and efficient rejection of divalent ions during nanofiltration process.

Mesoscopic Modeling Approach and Application for Steel Fiber Reinforced Concrete under Dynamic Loading:A Review

Steel fiber reinforced concrete(SFRC)has drawn extensive attention in recent years for its superior mechanical response to dynamic and impact loadings.Based on the existing test results,the highstrength steel fibers embedded in a concrete matrix usually play a strong bridging effect to enhance the bonding force between fiber and the matrix,and directly contribute to the improvement of the post-cracking behavior and residual strength of SFRC.To gain a better understanding of the action behavior of steel fibers in matrix and further capture the failure mechanism of SFRC under dynamic loads,the mesoscopic modeling approach that assumes SFRC to be composed of different mesoscale phases(i.e.,steel fibers,coarse aggregates,mortar matrix,and interfacial transition zone(ITZ))has been widely employed to simulate the dynamic responses of SFRC material and structural members.This paper presents a comprehensive review of the state-of-the-art mesoscopic models and simulations for SFRC under dynamic loading.Generation approaches for the SFRC mesoscale model in the simulation works,including steel fiber,coarse aggregate,and the ITZ between them,are reviewed and compared systematically.The material models for different phases and the interaction relationship between fiber and concrete matrix are summarized comprehensively.Additionally,some example applications for SFRC under dynamic loads(i.e.,compression,tension,and contact blast)simulated using the general mesoscale models are given.Finally,some critical analysis on the current shortcomings of the mesoscale modeling of SFRC is highlighted,which is of great significance for the future investigation and development of SFRC.

Study on Glass Fiber Dispersion Technology in SiO_2 Aerogel-glass Fiber Composite Insulation Materials

In order to improve the mechanical properties of SiO_2 aerogel-glass fiber composites, effects of different solvents(cyclohexane, n-hexane, ethanol, acetone) and different dispersing modes(planetary ball milling, ultrasonic dispersion and mechanical stirring) and dispersing duration(10-40 min) on the dispersion of chopped alkali-free glass fiber bundles were studied to determine the best dispersion process. On this basis, the materials were batched according to the mass fraction of SiO_2 aerogel powder to chopped alkali free glass fiber bundles of 90:10, and a certain amount of zinc oxide light-screening agent and phenolic resin binder were added. SiO_2 aerogel glass fiber composite specimens were prepared by direct adding chopped alkali free glass fiber bundles and pre-dispersed chopped alkali free glass fiber bundles, respectively. The cold crushing strength and the thermal conductivity at different surface temperatures(300, 400, 500 and 600 ℃, respectively)of the specimens were measured. The results show that:(1) the optimum dispersion process of chopped alkali-free glass fiber bundles is using ethanol as solvent and mechanical stirring for 30 min;(2) pre-dispersion of chopped alkali-free glass fiber bundles has little effect on the thermal conductivity of SiO_2 aerogel-glass fiber composites but can improve the cold crushing strength.

A Fiber Pull-Out Based Model for Synthetic Fiber Reinforced Concrete Beams under a Flexural Load

This work is intended to be a simple contribution to building a model able to implement theoretical results related to the random oriented fiber reinforced concrete in a procedure that could be used in structures analysis and design involving fiber reinforced elements. Here follows a short outline: In the introduction chapter the problem is presented together the work done. Section 2 develops some ancillary concepts of this material and its mechanical properties, while in Section 3, following the path of other researchers, the assumptions made to solve the problem are presented, together with the most relevant results related to presence of 3D randomly oriented fiber. In the following section a review of the mechanical process of fiber pull-out is done, and the results, mostly due to Victor Li researches, of a 3D randomly oriented synthetic fiber stress vs crack opening in a pull-out process from a cement matrix. In Section 5 the author, after making some assumptions about the configuration of the strain and crack geometry in the cross section where failure is assume to occur under flexural bending moment, the resultant stress is integrated to find the resultant internal moment vs increasing strain and crack width. In this analysis, the crack bridging law for synthetic fiber in FRC presented in the previous section is taken into account. In Section 6, a procedure to find a cross section configuration in equilibrium under external bending moment has been built. Under the assumption of a perfectly plastic collapse mechanism a numerical simulation is conducted on a specimen that undergoes a four-point bending test. A comparison with the trend of a similar test on a synthetic FRC sample has been done. The work is completed by the conclusions that could be inferred from this work.

INFLUENCE OF LOADING RATE ON DYNAMIC FRACTURE BEHAVIOR OF FIBER-REINFORCED COMPOSITES

The effect of loading rate on the dynamic fracture properties and the failure mechanisms of glass fiber-reinforced composite materials under mode I fracture is studied. Dynamic reflective caustic experiments are carried out for two loading rates. By measuring the characteristic dimensions of the shadow spots during the caustic experiments, the dynamic SIFs are calculated for different loading rates. The experimental results indicate that the dynamic fracture toughness Kid increases remarkably with increasing loading rate, and the crack grows faster under the high-velocity impact. Moreover, by examining the crack growth routes and the fracture surfaces, it is shown that the loading rate also greatly affects the failure mechanisms at micro-scale.

Manufacturing of Ultra-high Molecular Weight Polyethylene Fiber Reinforced Tape and the Loss of Strength

Due to the low density and excellent mechanical proper-ties,high performance fiber reinforced materials have aconsiderable application in the area of high technologyand dally usage.In this paper,the Ultra-high Molecu-lar Weight Polyethylene(UHMWPE)fiber reinforcedPE tape prepared with the method of powder impregnat-ion was studied.The effect of impregnate length and thetensile force of the yarn on the fiber content as well as on the strength and modulus of the tape were discussed.Calculation shows that the strength and the modulus ofthe ULMWPE fiber can keep about 85％ after it undergothe process.

Effect of Loading Frequency on the High Cycle Fatigue Strength of Flax Fiber Reinforced Polymer Matrix Composites

Among natural fibers,flax fiber reinforced polymer matrix composites show excellent dynamic/fatigue properties due to its excellent damping properties.Knowledge about fatigue limit and effect of loading frequency on fatigue limit is very crucial to know before being used a member as a structural component.Fatigue limit of fiber reinforced composite is measured through high cycle fatigue strength(HCFS).The effect of loading frequency on the HCFS of flax fiber reinforced polymer matrix composites was investigated using stabilized specimen surface temperature based thermographic and dissipated energy per cycle-based approaches.Specimens of unidirectional flax fiber reinforced thermoset composites were tested under cyclic loading at different percentages of applied stresses for the loading frequencies of 5,7,10,and 15 Hz in order to determine the stabilized surface temperature of the specimen and dissipated energy per fatigue cycle.Both approaches predicted similar fatigue limits(HCFS)which showed a good agreement with experimental results from Literature.HCFS of flax fiber reinforced composites decrease little with increasing loading frequency.Furthermore,effect of loading frequency on stabilized specimen temperature and dissipated energy per fatigue cycle was also investigated.Although specimen surface temperature increases with loading frequency,dissipated energy per-cycle does not change with loading frequency.Thermal degradation at higher loading frequencies may play a significant role in decreasing HCFS with increasing loading frequency.

含缺陷管道碳纤维复合材料补强数值模拟研究

当代石油、天然气等能源的主要运输方式为管道运输,管道在长期使用时会产生各种缺陷,这些缺陷将对管道的结构和强度产生影响。目前先进的管道修复技术为复合材料补强技术,其中碳纤维复合材料是较优的选择。为了测试有/无碳纤维补强管道缺陷处的效果,开展了不同层数碳纤维复合材料的拉伸实验研究,结合ANSYS数值模拟探究了修复前后不同缺陷管道在承载时的应力、应变分布,分析了修复补强效果的影响因素。结果表明:缺陷减薄厚度对管道的应力、应变状态影响较大,碳纤维复合材料修复技术能在减小管道缺陷处应力、应变的同时优化其应力、应变分布,可以通过增加碳纤维修复层数来提升修复效果,相关研究对于管道的修复补强有一定指导意义。

基于像素标记法的复合材料异型构件均匀性表征

纤维增强陶瓷基复合材料由孔隙缺陷引起的结构不均匀会严重影响构件的宏观力学性能,而整体孔隙率无法有效表征均匀性。针对此问题,提出了一种基于像素标记的空间区块划分方法,实现对异型构件CT扫描体数据的自动分块。在计算出每个区块体孔隙率值的基础上,以孔隙率均值与标准差的乘积为指标,对构件结构均匀性进行定量表征。采用光线投射法对孔隙率进行三维映射,对孔隙率分布进行直观的可视化表征。结果表明:该方法能有效定量表征出异型构件整体及局部均匀性,并从三维角度给出构件局部孔隙率的大小、空间位置信息,为进一步优化制造工艺参数、提高构件服役的可靠性提供了有力依据。

掺废弃陶瓷纤维增强水泥基复合材料抗冻性能

采用陶瓷粉替代一部分水泥,陶瓷砂替代普通河砂,在水泥基材料中掺入不同体积掺量的聚乙烯醇(Polyvinyl Alcohol,PVA)纤维,制成掺入PVA纤维和陶瓷粉的水泥基复合材料砂浆试件。通过冻融循环试验分析质量损失率、相对动弹性模量的变化,并通过电化学阻抗测试和扫描电子显微镜观察研究砂浆试件的冻融损伤规律。结果表明:陶瓷粉中SiO_(2)和Al_(2)O_(3)含量远大于水泥中相应含量,且粒径小于20μm的颗粒占82.3%,火山灰效应和微集料效应可改善试件的密实度,提升复合材料的抗冻性能;PVA纤维掺量为2.2%,陶瓷粉掺量为30%,冻融循环100次时砂浆试件质量损失率最小,相对动弹性模量最大,连续导电路径电阻最大,冻融损伤程度最小;纤维和基体的接触面是该复合材料抗冻薄弱部位。

碳纤维复合材料在建筑加固工程中的应用

碳纤维复合材料具有强度高、质量轻等特点,在建筑加固工程中应用的碳纤维材料包含碳纤维板及碳纤维布两种,其加固操作简单、适用面广,相比传统加固方式优势明显。本文主要分析了碳纤维复合材料的加固原理及其优势,介绍了碳纤维复合材料在建筑加固中所应用的内嵌入式及外贴式加固方法,并对未来的应用做出展望,以期能够为碳纤维复合材料在建筑加固工程中的使用提供借鉴意义。

FRP布材增强钢筋混凝土桩水平承载性能研究

纤维增强复合材料(FRP)由于其轻质高强的优点被广泛应用于抗震加固、结构补强等实际工程中,但有关FRP增强混凝土桩水平承载性能的研究较少。为了研究不同FRP布材加固混凝土桩承载特性问题,通过室内模型试验对FRP布桩(普通钢筋混凝土桩身包裹FRP布材)的水平承载规律进行研究,探究了不同包裹层数、不同FRP布材类型、不同布材混合包裹对钢筋混凝土桩承载性能的影响。同时利用ABAQUS软件建立FRP布桩三维有限元模型,对每种工况进行数值模拟。结果表明,FRP布桩的水平承载性能随着包裹层数的增加而提升,提升效果与包裹层数之间并不存在正比例关系;不同布材类型的FRP布桩中,CFRP布对FRP布桩的水平承载性能提升效果最优;混合包裹(CFRP+GFRP)的提升效果要略优于包裹2层GFRP布。

浅谈建筑结构加固工艺

我国在基础建设快速发展的阶段,进一步加大了对基础设施建设的投入,从而加快了建筑业的发展,充分发挥国家科技力量的支撑作用,相继修建了各种类型的道路、桥梁、高楼、会展中心、重大水利工程等。由于受到自然灾害、空气影响等,这些建筑的结构往往出现过早老化的情况。据相关统计数据显示,全国城镇需要开展加固工作的民用建筑有30亿平方米,其中亟待修复加固处理的建筑有10亿平方米。如何对这些老旧建筑检测加固,需要进行研究探讨。

树脂基纤维复合材料在新能源汽车上的应用

树脂基纤维复合材料具有密度小、模量高、比强度高等优点,是优异的车用轻量化材料。为更好地探寻新能源汽车零部件的用材趋势,文章对树脂基纤维复合材料在国内外新能源汽车上的应用进行了详细的分析。研究发现,碳纤维增强复合材料虽然成本高,但由于优异的性能,仍在部分高端车型上大量使用,用以提升品牌影响力;玻纤增强复合材料,成本较低,是理想的轻量化材料,近几年在新能源汽车上大量应用;天然纤维增强复合材料的应用主要是为了提升低碳、环保的形象;玄武岩纤维增强复合材料目前还未形成完整的产业链,但未来有广阔的发展空间。文章的分析为新能源汽车零部件的选材提供了依据和指引方向。