Regulatable Orthotropic 3D Hybrid Continuous Carbon Networks for Efficient Bi-Directional Thermal Conduction

Vertically oriented carbon structures constructed from low-dimen-sional carbon materials are ideal frameworks for high-performance thermal inter-face materials(TIMs).However,improving the interfacial heat-transfer efficiency of vertically oriented carbon structures is a challenging task.Herein,an orthotropic three-dimensional(3D)hybrid carbon network(VSCG)is fabricated by depositing vertically aligned carbon nanotubes(VACNTs)on the surface of a horizontally oriented graphene film(HOGF).The interfacial interaction between the VACNTs and HOGF is then optimized through an annealing strategy.After regulating the orientation structure of the VACNTs and filling the VSCG with polydimethylsi-loxane(PDMS),VSCG/PDMS composites with excellent 3D thermal conductive properties are obtained.The highest in-plane and through-plane thermal conduc-tivities of the composites are 113.61 and 24.37 W m^(-1)K^(-1),respectively.The high contact area of HOGF and good compressibility of VACNTs imbue the VSCG/PDMS composite with low thermal resistance.In addition,the interfacial heat-transfer efficiency of VSCG/PDMS composite in the TIM performance was improved by 71.3%compared to that of a state-of-the-art thermal pad.This new structural design can potentially realize high-performance TIMs that meet the need for high thermal conductivity and low contact thermal resistance in interfacial heat-transfer processes.

Poly [ (chloromethyl) styrene-co-divinylbenzene] Continuous Rod Column of Weak Cation Exchange Chromatography and its Applications in the Separation of Biopolymers

Macroporous poly [(chloromethyl) styrene-co-divinylbenzene] continuous rod was prepared by direct polymerization of the monomers in the presence of a porogenic diluent inside an empty chromatographic column. A new 'in-situ' technique was used to modify the synthesized polymer rod for a weak cation exchanger and it has been used successfully for the separation of biopolymers. It was found that the back pressure of the continuous rod column was much lower and its surface was proved to be modified well.

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part II:Analytical study

Strengthening reinforced concrete (R. C.) beams using prestressed glass fiber-reinforced polymer (PGFRP) was studied experimentally as described in Part I of this paper (Huang et al., 2005). In that paper, R. C. beams, R. C. beams with GFRP (glass fiber-reinforced polymer) sheets, and R. C. beams with PGFRP sheets were tested in both under-strengthened and over-strengthened cases. The test results showed that the load-carrying capacities (ultimate loads) of the beams with GFRP sheets were greater than those of the beams without polymer sheets. The load-carrying capacities of beams with PGFRP sheets were greater than those of beams with GFRP sheets. The objective of this work is to develop an analytical method to compute all of these load-carrying capacities. This analytical method is independent of the experiments and based only on the traditional R. C. and P. C. (prestressed concrete) theory. The analytical results accorded with the test results. It is suggested that this analytical method be used for analyzing and designing R. C. beams strengthened using GFRP or PGFRP sheets.

Fiber-Reinforced Polymer Bridge Design in the Netherlands： Architectural Challenges toward Innovative, Sustainable, and Durable Bridges

This paper reviews the use of fiber-reinforced polymers （FRPs） in architectural and structural bridge design in the Netherlands. The challenges and opportunities of this relatively new material, both for the architect and the engineer, are discussed. An inventory of recent structural solutions in FRP is included, followed by a discussion on architectural FRP applications derived from the architectural practice of the author and of other pioneers.

Compressive Strength Estimation for the Fiber-Reinforced Polymer (FRP)-Confined Concrete Columns with Different Shapes Using Artificial Neural Networks

An evaluation of existing strength of concrete columns confined with fiber-reinforced polymer( FRP) was presented with extensive collection of experimental data. According to the evaluation results, artificial neural networks( ANNs) model to predict the ultimate strength of FRP confined column with different shapes was proposed. The models had seven inputs including the column length,the tensile strength of the FRP in the hoop direction,the total thickness of FRP,the diameter of the concrete specimen,the elastic modulus of FRP,the corner radius and the concrete compressive strength. The compressive strength of the confined concrete was the output data. The results reveal that the proposed models have good prediction and generalization capacity with acceptable errors.

Continuous Deformation Monitoring by Polymermatrix Carbon Fiber Sensitive Layer

Composite made of short-cut carbon fiber mat and vinyl ester resin was observed to be an effective sensor for tensile strain up to 6 000με. Based on its strain sensitivity, a skin-like sensitive layer which can continuously cover the structural surface to sense strain in large area was developed. The sensitive layer was applied to continuously monitor the deformation of a simply supported beam. The result indicates that the fractional change in electrical resistance of the sensitive layer reversibly reflects the beam deformation in each section and describes the distribution of the average strain of the beam. The effect of temperature change on the monitoring was studied by monitoring tests conducted at different temperatures ranging from 20 to 80 ℃, which reveals temperature sensitivity in the sensitive layer and the temperature dependence of the piezoresistive behavior when the temperature exceeds 50 ℃. By the application of differential conaection principle, a method for temperature compensation was established and the gauge factor for the monitoring was dramatically increased. This method was verified experimentally.

CONTINUOUS THERMODYNAMICS FOR POLYMER SOLUTIONS I.CLOSE-PACKED LATTICE MODEL

using close-packed lattice models,a continuous thermodynamic framework is presented forphase-equilibrium calculations for binary solutions with a polydisperse polymer solute.An expressionfor the Helmholtz function of mixing is based on the revised Freed model developed previously.Asize parameter c_r and an energy parameter ε are used;the former can be temperature dependent,while the latter can depend on both temperature and chain-length of the polymer.The discretemulticomponent approach is adopted to derive expressions for chemical potentials,spinodals and criti-cal points.The continuous distribution function is then used in calculations of moments occurring inthose expressions.Computation programs are established for cloud-point-curve,shadow-curve,spinodal and critical-point calculations for polymer solutions with standard distribution or arbitrarydistribution of polymer.In the latter case,the derivative method developed previously is applied.lllustrations for phase-equilibrium calculations are

CONTINUOUS THERMODYNAMICS FOR POLYMER SOLUTIONS II . LATTICE FLUID MODEL

Using lattice-fluid model, a continuous thermodynamic framework is presented for phase-equilibrium calculations for binary solutions with a polydisperse polymer solute. A two-step process is designed to form a real polymer solution containing a solvent and a polydisperse polymer solute occupying a volume at fixed temperature and pressure. In the first step, close-packed pure components including solvent and polymers with different molar masses or different chain lengths are mixed to form a closed-packed polymer solution. In the second step, the close-packed mixture, considered to be a pseudo-pure substance is mixed with holes to form a real polymer solution with a volume dependent on temperature and pressure. Revised Freed's model developed previously is adopted for both steps. Besides pure-component parameters, a binary size parameter cr and a binary energy parameter e12 are used. They are all temperature dependent. The discrete-multicomponent approach is adopted to derive expressions for chemical potentials, spinodals and critical points. The continuous distribution function is then used in calculations of moments occurring in those expressions. Computation procedures are established for cloud-point-curve, shadow-curve, spinodal and critical-point calculations using standard distribution or arbitrary distribution on molar mass or on chain length. Illustrative examples are also presented.

Additive Manufacturing of Continuous Fiber-Reinforced Polymer Composite Sandwich Structures with Multiscale Cellular Cores

The use of composite sandwich structures with cellular cores is prevalent in lightweight designs owing to their superior energy-absorbing abilities.However,current manufacturing processes,such as hot-press molding and mold pressing,require multiple steps and complex tools,thus limiting the exploration of advanced sandwich structure designs.This study reports a novel multi-material additive manufacturing(AM)process that allows the single-step production of continuous fiber-reinforced polymer composite(CFRPC)sandwich structures with multiscale cellular cores.Specifically,the integration of CFRPC-AM and in situ foam AM processes provides effective and efficient fabrication of CFRPC panels and multiscale cellular cores with intricate designs.The cellular core design spans three levels:microcellular,unit-cell,and graded structures.Sandwich structures with a diverse set of unit-cell designs,that is,rhombus,square,honeycomb,and re-entrant honeycomb,were fabricated and their flexural behaviors were studied experimentally.The results showed that the sandwich structure with a rhombus core design possessed the highest flexural stiffness,strength,and specific energy absorption.In addition,the effect of the unit-cell assembly on the flexural performance of the CFRP composite sandwich structure was examined.The proposed design and fabrication methods open new avenues for constructing novel and high-performance CFRPC structures with multiscale cellular cores that cannot be obtained using existing approaches.

Proposed numerical and machine learning models for fiber-reinforced polymer concrete-steel hollow and solid elliptical columns

This study employs a hybrid approach,integrating finite element method(FEM)simulations with machine learning(ML)techniques to investigate the structural performance of double-skin tubular columns(DSTCs)reinforced with glass fiber-reinforced polymer(GFRP).The investigation involves a comprehensive examination of critical parameters,including aspect ratio,concrete strength,number of GFRP confinement layers,and dimensions of steel tubes used in DSTCs,through comparative analyses and parametric studies.To ensure the credibility of the findings,the results are rigorously validated against experimental data,establishing the precision and trustworthiness of the analysis.The present research work examines the use of the columns with elliptical cross-sections and contributes valuable insights into the application of FEM and ML in the design and evaluation of structural systems within the field of structural engineering.

An efficient improved Gradient Boosting for strain prediction in Near-Surface Mounted fiber-reinforced polymer strengthened reinforced concrete beam

The Near-Surface Mounted(NSM)strengthening technique has emerged as a promising alternative to traditional strengthening methods in recent years.Over the past two decades,researchers have extensively studied its potential,advantages,and applications,as well as related parameters,aiming at optimization of construction systems.However,there is still a need to explore further,both from a static perspective,which involves accounting for the nonconservation of the contact section resulting from the bond-slip effect between fiber-reinforced polymer(FRP)rods and resin and is typically neglected by existing analytical models,as well as from a dynamic standpoint,which involves studying the trends of vibration frequencies to understand the effects of various forms of damage and the efficiency of reinforcement.To address this gap in knowledge,this research involves static and dynamic tests on simply supported reinforced concrete(RC)beams using rods of NSM carbon fiber reinforced polymer(CFRP)and glass fiber reinforced polymer(GFRP).The main objective is to examine the effects of various strengthening methods.This research conducts bending tests with loading cycles until failure,and it helps to define the behavior of beam specimens under various damage degrees,including concrete cracking.Dynamic analysis by free vibration testing enables tracking of the effectiveness of the reinforcement at various damage levels at each stage of the loading process.In addition,application of Particle Swarm Optimization(PSO)and Genetic Algorithm(GA)is proposed to optimize Gradient Boosting(GB)training performance for concrete strain prediction in NSM-FRP RC.The GB using Particle Swarm Optimization(GBPSO)and GB using Genetic Algorithm(GBGA)systems were trained using an experimental data set,where the input data was a static applied load and the output data was the consequent strain.Hybrid models of GBPSO and GBGA have been shown to provide highly accurate results for predicting strain.These models combine the strengths of both optimization techniques to create a powerful and efficient predictive tool.

Preparation and properties of continuous Al-containing silicon carbide fibers

Continuous SiC(OAl) fibers, named KD-A fibers, were prepared by the melt-spinning of ceramic precursor polyaluminocarbosilane, air-curing, and pyrolizing at 1 300 ℃. These fibers contained small amount of aluminum and 7%- 9% oxygen. The KD-A fibers were converted into sintered SiC(Al) fibers, named KD-SA, by sintering at 1 800 ℃. The fibers were characterized by chemical analysis, tensile strength test, SEM and XRD. The tensile strength, elastic modulus and diameter of the KD-A fibers are 2.6 GPa, 210 GPa, 12 - 14 μm, respectively. The KD-A fibers have higher thermal stability, more excellent oxidation resistance than the Nicalon fibers. The properties of the KD-A fibers have reached the level of Hi-Nicalon fibers. The tensile strength, elastic modulus and diameter of the KD-A fibers are 2.1 GPa, 405 GPa, 10 - 12 μm, respectively. The KD-SA fibers with nearly stoichiometric component have stable performance at high temperature, and better creep resistance than the Tyranno SA fibers.

Deriving Tensile Properties of Glass Fiber Reinforced Polymers (GFRP) Using Mechanics of Composite Materials

This work addresses the tensile properties of glass fiber reinforced polymers (GFRP) and investigates the different ways of estimating them without the cost associated with experimentation. This attempt is achieved through comparison between experimental results, derived in accordance with the ASTM standards, and results obtained using the mechanics of composite materials. The experimental results are also compared to results derived from work by other researchers in order to corroborate the findings regarding the correlation of tensile properties of the GFRP material and the fiber volume fraction.

Flexure-Compression Testing of Bridge Timber Piles Retrofitted with Fiber Reinforced Polymers

The adequacy of using Fiber Reinforced Polymer (FRP) retrofit technique to restore the flexure-compression behavior of deteriorated bridge timber piles is examined experimentally in this paper. Sixteen specimens are tested monotonically under eccentric compressive loading. The specimens are first tested in their unretrofitted condition to determine their elastic properties. Each specimen is then cut and connected (posted) using the proposed FRP retrofit technique, and retested. The results show that the retrofitted specimens are capable of reaching same or higher strengths than that of the unretrofitted specimens with minimal reduction in their stiffness. Based on the experimental results, a design equation is presented to compute the volumetric ratio of FRP needed for retrofitting bridge timber piles under eccentric load.

A Voronoi diagram approach for detecting defects in 3D printed fiber-reinforced polymers from microscope images

Fiber-reinforced polymer(FRP)composites are increasingly popular due to their superior strength to weight ratio.In contrast to significant recent advances in automating the FRP manufacturing process via 3D printing,quality inspection and defect detection remain largely manual and inefficient.In this paper,we propose a new approach to automatically detect,from microscope images,one of the major defects in 3D printed FRP parts:fiber-deficient areas(or equivalently,resin-rich areas).From cross-sectional microscope images,we detect the locations and sizes of fibers,construct their Voronoi diagram,and employ-shape theory to determine fiber-deficient areas.Our Voronoi diagram and-shape construction algorithms are specialized to exploit typical characteristics of 3D printed FRP parts,giving significant efficiency gains.Our algorithms robustly handle real-world inputs containing hundreds of thousands of fiber cross-sections,whether in general or non-general position.

3D打印连续纤维复合材料工艺、结构优化研究进展

连续纤维增强复合材料由于优异的比强度、比刚度、可设计性和轻量化特质,日益受到航空航天等高端装备制造领域的青睐.3D打印技术的发展改变了连续纤维复合材料结构的生产制造流程,使复杂结构的自由成型成为可能,为先进结构材料提供了巨大的设计空间.为充分发挥先进材料性能优势和3D打印成型灵活性,研究人员分别从材料性能和结构设计出发,探索与3D打印连续纤维复合材料相适应的设计制造一体化解决方案,实现产品创新设计和性能提升.本文系统性地回顾了面向连续纤维复合材料性能分析、工艺改进和结构优化的研究工作,结合研究实践对连续纤维复合材料的结构多尺度优化方法进行总结分析,并对未来先进材料结构设计实时化、功能化、智能化的发展趋势进行探讨和展望.

双转子连续混炼设备的进展

双转子连续混炼机由于具有稳定、高效和节能的特点,在聚合物材料加工领域得到了广泛的应用。首先综述了双转子连续混炼机的国内外研发历程,梳理了双转子连续混炼机系统结构设计、转子结构优化和加工机理等的研究进展,并系统地分析了转子的楔入角、转子的螺棱数和转子的相位角等重要转子结构参数对聚合物材料结构与性能的影响。另外,总结了双转子连续混炼机在高填充母料、超高分子量聚乙烯(UHMWPE)加工和回收橡胶等领域的应用进展。最后,概述了双转子连续混炼设备的发展趋势,需要深入研究其加工机理,并且,不断朝着大型化、专业化、绿色化和智能化方向发展。

小半径曲线简支梁桥上有轨电车嵌入式轨道无缝线路研究

为研究小半径曲线简支梁桥上有轨电车嵌入式轨道无缝线路的力学特性,根据梁轨纵向和横向相互作用原理,采用有限元法建立三维曲线简支梁桥上嵌入式轨道无缝线路模型,详细分析了钢轨温度、曲线半径、高分子材料纵向阻力和横向刚度对钢轨和桥梁纵、横向受力和变形的影响规律。结果表明:(1)钢轨温度的增加会显著加剧伸缩工况中梁轨横向相互作用,故在进行小半径曲线桥上无缝线路设计时,需要考虑钢轨温度对桥墩横向受力的影响;(2)随着曲线半径的增加,钢轨伸缩力和梁轨纵向相对位移逐渐增加,梁轨横向相对位移和桥梁墩台横向受力则呈现整体减小的变化趋势;(3)当曲线半径大于300 m时,梁轨纵、横向相互作用与直线模型的计算结果逐渐趋于一致;(4)降低高分子材料纵向阻力可以显著减小桥梁墩台纵向和横向受力,对无缝线路力学特性而言,高分子材料横向刚度不是一个十分敏感的参数;(5)曲线半径对伸缩工况和断轨工况的影响较为显著,而对挠曲工况和制动工况的影响相对较小;(6)采用直线模型的计算结果进行钢轨强度和断缝值检算是偏安全的,但在检算小半径曲线地段桥梁墩台横向受力时需要采用曲线模型。

聚合物水泥防水涂料用苯丙乳液的研制及其各因素影响研究

通过预乳化半连续种子乳液聚合法自制了JS防水涂料专用苯丙乳液,并由此制备了聚合物水泥防水涂料。研究了乳化剂用量及其分配对苯丙乳液粒径及其吸水率的影响,同时通过尝试不同的方法降低乳液残留单体减少VOC排放。在自制苯丙乳液的基础上探究不同液粉比对聚合物水泥防水涂料拉伸性能的影响,通过添加一些不同的助剂来提升聚合物水泥防水涂料的综合性能。

利用原生聚酯装置进行PET废料化学法醇解回收

本文介绍了在连续原生聚酯装置浆料配制系统或者酯化一釜中加入PET废料进行化学法醇解回收的工艺流程及经济收益。该技术具有固定资产投资成本低、产品品质好、经济效益高等一系列优势。在节约资源、保护环境的同时又能提高企业的经济效益。