防热复合材料发展与展望

以烧蚀型防热复合材料、 非(微)烧蚀型防热复合材料、 高温高效隔热复合材料以及高温透波复合材料为重点, 简要总结了国内外防热复合材料发展现状, 介绍了我国重点领域的突破与进展, 并展望了未来防热复合材料的发展趋势。      

Enhancing the Deformation of Shape Memory Sandwich Panels

Abstract: Composite sandwich panels fabricated using a thermosetting shape memory polymer matrix material and a corresponding thermoset shape memory polymer foam core offer the potential to demonstrate large, recoverable, deformations in otherwise stiff structures, under flexural loading. However, as with flexure of thin, fibre‐reinforced shape memory matrix laminates, deflection is limited by fibre compression buckling because of the reduced shape memory matrix stiffness at elevated temperature. A hybrid matrix concept has been developed for sandwich panels loaded in flexure in a single direction. This concept uses a non‐shape memory resin as the matrix for a fraction of the plies on the surface of the facesheet loaded in compression. It is predicted that, at the elevated temperatures required for the generation of deformation in the shape memory structural sandwich panel, the shape memory matrix and foam moduli will be substantially reduced, while the modulus of the non‐shape memory resin will not. Thus, at elevated temperature this effectively leads to a shift of the neutral axis towards the non‐shape memory surface, keeping the low stiffness shape memory matrix material in tension and extending the range of deformation prior to onset of fibre buckling. The experiments performed demonstrate that this hybrid matrix approach enables a three‐fold increase in mid‐span deformation prior to buckling of fibres in the compression surface plies. Furthermore, the force measured to attain the deformed geometry, at elevated temperature, only increases approximately 10–15%, while the magnitude of the force required remains very low. Thus, the hybrid matrix approach functions as predicted and enables the development of sandwich panel structural elements which can undergo large, recoverable deformations.     

A study of continuous filament reinforced aluminum matrix composites

Some principal results of the research work on metal matrix composites at Beijing Institute of Aeronautical Materials, concerning CVD-produced continuous B and SiC filaments reinforced aluminum and its alloys, are summarized. The processing, fiber degradation, interface, mechanical properties and fracture behavior of the composites are discussed.Abbreviations CVD chemical vapor deposition - MMCs metal matrix composites - ROM rule of mixtures     

Structural composites for multifunctional applications: Current challenges and future trends

This review paper summarizes the current state-of-art and challenges for the future developments of fiber-reinforced composites for structural applications with multifunctional capabilities. After a brief analysis of the reasons of the successful incorporation of fiber-reinforced composites in many different industrial sectors, the review analyzes three critical factors that will define the future of composites. The first one is the application of novel fiber-deposition and preforming techniques together with innovative liquid moulding strategies. The second is the combination of these techniques by optimization tools based on novel multiscale modeling approaches, so fiber-reinforced composites with optimized properties can be designed and manufactured for each application. In addition, the third is the enhancement of composite applications by the incorporation of multifunctional capabilities. Among them, electrical conductivity, energy storage (structural supercapacitors and batteries) and energy harvesting (piezoelectric and solar energy) seem to be the most promising ones.     

高分子复合隐身材料的研究进展

在简要介绍高分子复合材料分类的基础上,重点综述了不同高分子复合隐身材料的合成与制备方法及特点,并评述了高分子复合隐身材料在吸波隐身技术上的应用进展,展望了其发展趋势。     

先进复合材料:过去、现在和将来

本文简要回顾了先进复合材料的发展历史。重点评述了聚合物基、金属基、陶瓷基和碳/碳复合材料的最新进展和现状。并对各类先进复合材料的未来进行了展望。     

Hybrid effective medium approximations for random elastic composites

Several popular effective medium approximations for elastic constants of random composites are reformulated in terms of a pair of canonical functions and their transform variables. This choice of reformulation enables easier comparisons of the results of all these methods with rigorous bounds. Furthermore, insight into the various methods gained by taking this point of view suggests a number of new effective medium approximations that, in some cases, are natural variants and/or combinations (i.e., hybrids) of the existing ones, and in other cases are new ones based in part on the bounds themselves. Numerical comparisons are given for several standard inclusion models — including spherical, needle, and penny-shaped inclusions — as well as the penetrable sphere model. Of the various alternatives considered, a new method called the split-step differential (SSD) scheme is one of the more useful ones, as it simplifies the differential scheme by replacing half of this scheme’s integration routines with a simple update formula for the bulk modulus.     

Shape control of NITINOL-reinforced composite beams

The shape of composite beams is controlled by sets of flat strips of a shape memory nickel–titanium alloy (NITINOL). The strips are embedded in the composite fabric of these beams inside sleeves, which are placed on the neutral axes. Prior to their insertion inside the beams, the NITINOL strips are thermally trained to provide and memorize controlled transverse deflections. Proper activation of the shape memory effect of the appropriate strips is utilized to produce controlled shapes of the NITINOL-reinforced beams.

A mathematical model is developed to describe the behavior of this class of SMART composites. The model describes the interaction between the elastic characteristics of the composite beams and the thermally induced shape memory effect of the NITINOL strips. The effect of various activation strategies of the NITINOL strips on the shape of the composite beams is determined.

The theoretical predictions of the model are validated experimentally using a fiberglass composite beam made of 8 plies of unidirectional BASF 5216 prepregs, which are 9.75 cm wide and 21.20 cm long. The beams are provided with four NITINOL-55 strips, which are 1.2 mm thick and 1.25 cm wide. The time response characteristics of the beam are monitored and compared with the corresponding theoretical characteristics. Close agreement is obtained between the theoretical predictions and the experimental results. The obtained results suggest the potential of the NITINOL strips in controlling the shape of composite beams without compromising their structural stiffness.     

FCVI工艺研究进展

强制流动热梯度化学气相渗透（ＦＣＶＩ）作为一种制备碳基与陶瓷基复合材料的新工艺，克服了传统ＣＶＩ中气体扩散传输与预制体渗透的限制，可在短时间内制备出密度均匀性能优良的制作，本文对ＦＣＶＩ技术进行了概要评述，主要内容包括ＦＣＶＩ的基本特点，预制体准备，工艺参数分析以及模型与模拟等。     

2014 and 6061 aluminium alloy-based powder metallurgy composites containing silicon carbide particles/fibres

The present investigation covers the processing and mechanical properties of 2014 and 6061 Al alloy-based power metallurgy composites containing up to 8 vol% of SiC in either particle or continuous fibre form. For consolidation of the green compacts, liquid phase sintering under vaccum at 635°C was adopted. The addition of reinforcement imparted improved densification such that particulate composites were better densified than the fibrous ones. Relatively higher work hardening rates were observed in fibrous composites than in the particulate ones. The ductility values of obtained porous particulate composites were similar to those of the fully dense ones reported in the literature.     

Conductivity in carbon nanotube polymer composites: A comparison between model and experiment

Carbon nanotubes (CNTs) demonstrate remarkable conductive behaviour, which suggests promising applications. Their outstanding properties have been used in the development of CNT–polymer composites as possible alternative materials for various applications, such as flexible electrodes, antistatic coatings and piezoresistive sensors. In our study we focused our attention on the evaluation and modelling of CNT-filled epoxy resin electrical conductivity. We discuss the results with regard to the influence of CNTs dimensions and content. Exploiting the Dijkstra algorithm, we implemented a simulation code which determines the shortest route between electrodes in the polymer. The longer the path inside the polymer, the more non-conductive the composite becomes, since polymer resistivity is orders of magnitude higher than that of CNTs. We compared these simulated results with experimental data obtained at several wt% and found a good correspondence between modelling and experimental results.     

Mineralized structures in nature: Examples and inspirations for the design of new composite materials and biomaterials

Through the natural evolutionary process, organisms have been improving amazing mineralized materials for a series of functions using a relatively few constituent elements. Biomineralization has been widely studied in the last years. It is important to understand how minerals are produced by organisms and also their structure and the corresponding relationship with the properties and function. Moreover, one can look at minerals as a tool that could be used to develop high performance materials, through design inspiration and to find novel processing routes functioning at mild conditions of temperature, pressure and solvent type. As important as the molecular constituents are structural factors, which include the existence of different levels of organization and controlled orientation. Moreover, the way how the hierarchical levels are linked and interfacial features plays also a major role in the final behavior of the biogenic composite. The main aim of this work is to review the latest contributions that have been reported on composite materials produced in nature, and to relate their structures at different length scales to their main functions and properties. There is also an interest in developing new biomimetic procedures that could induce the production of calcium phosphate coatings, similar to bone apatite in substrates for biomedical applications, namely in orthopedic implants and scaffolds for tissue engineering and regenerative medicine; this topic will be also addressed. Finally, we also review the latest proposed approaches to develop novel synthetic materials and coatings inspired from natural-based nanocomposites.     

Recent research and development,future problems and trends in advanced composite materials in Japan

The progress and contributions of the national research and development project on advanced composites so far are described, some structural applications of composites in Japan are outlined to examine the structural utility. Future problems and trends are also considered.     

绿色复合材料的研究进展

天然植物纤维具有价廉质轻、比强度高和自然降解等优良特性,其与生物降解树脂进行复合,能开发出环境友好、可自然降解的绿色复合材料.本文评述了该领域的研究进展,重点是竹纤维、各种麻纤维以及甘蔗渣纤维等天然纤维与不同的生物降解树脂的绿色复合材料的制备,不同成型方法的探讨,材料各种力学性能的分析比较,以及为了增强材料的力学性能而进行的纤维改性,并展望了绿色复合材料的未来的研究趋势.     

木塑复合材料的发展回顾

由于具有经济和环保的优点,木塑复合材料在近些年得到了快速发展.本文主要回顾了国内外木塑复合材料的发展历史和研究现状.包括所研究的木塑复合材料的种类、力学行为的表征和特点、各种影响木塑复合材料力学性能的因素,以及为提高木塑复合材料力学性能而采取的物理和化学的处理方法和工艺.还介绍了一些用来研究木塑复合材料行为的实验手段.     

Research progress of ceramic matrix composite parts based on additive manufacturing technology

ABSTRACT

Ceramic matrix composites (CMCs) are materials that can be engineered for high-temperature applications in various fields including aerospace, marine, etc. It is very difficult to fabricate CMCs using traditional moulding methods due to their brittleness and high hardness. Additive manufacture (AM) technology, a digital manufacturing technology, provides multiple advantages over traditional manufacturing technologies, such as fabricating geometrically complex parts, mould-free fabrication, short development cycle, etc. In this paper, various AM technologies developed for CMCs are reviewed with emphasis on mechanisms of manufacturing, characteristics of production, and recent research progresses. With the springing up of innovative ideas and pioneering work, AM technology possesses unique forming capabilities in fabricating CMCs, demonstrating strong potentials in the application of CMCs in aerospace and other fields. However, there are still many challenges of CMCs fabricated by AM technologies, i.e. poor mechanical properties and geometric accuracies; lower reinforcement volume fraction than that of traditional manufacturing processes.     

Thermomechanical performance of composite materials

Summary A brief review of the status of modelling of thermostructural composites is given, emphasizing topics discussed at the workshop sessions. The perceived needs for new models and techniques to predict composite performance under loading conditions of importance in various industrial applications is discussed, with a summary of recommended areas for focussed near-term research.     

热结构复合材料的制备及应用

论述了热结构复合材料制造方法,包括泥浆浸注法、溶胶和聚合物热解法、熔体渗透法以及化学气相渗透法。扼要地分析了热结构复合材料的应用。