Epoxy‐Based Fibre Reinforced Nanocomposites

The modification of epoxy resins with nanoparticles could endow the materials with some superior properties such as broadening of the glass transition temperatures, modest increases in the glassy modulus, low dielectric constant, and significant increases in key mechanical properties. In the last 15 years, some studies have shown the potential improvement in properties and performances of fibre reinforced polymer matrix materials in which nano and micro‐scale particles were incorporated. From the existing literature, considerable effort has been given to the synthesis and processing of these unique polymers, but relatively little work has focused on the fibre reinforced epoxy composites. The purpose of this work, therefore, is to review the available literature in epoxy‐fibre reinforced composites manufactured using carbon nanotubes, carbon nanofibre and nanoclays for reinforcement.     

Recent Advances in Research on Carbon Nanotube–Polymer Composites

Carbon nanotubes (CNTs) demonstrate remarkable electrical, thermal, and mechanical properties, which allow a number of exciting potential applications. In this article, we review the most recent progress in research on the development of CNT–polymer composites, with particular attention to their mechanical and electrical (conductive) properties. Various functionalization and fabrication approaches and their role in the preparation of CNT–polymer composites with improved mechanical and electrical properties are discussed. We tabulate the most recent values of Young's modulus and electrical conductivities for various CNT–polymer composites and compare the effectiveness of different processing techniques. Finally, we give a future outlook for the development of CNT–polymer composites as potential alternative materials for various applications, including flexible electrodes in displays, electronic paper, antistatic coatings, bullet‐proof vests, protective clothing, and high‐performance composites for aircraft and automotive industries.     

Electrical conductivity of water- based nanofluids prepared with graphene – carbon nanotube hybrid

Graphene, Carbon Nanotubes and their hybrids are receiving considerable attention in energy storage devices due to their unique properties. The present study reports the synthesis of Graphene–Carbon Nanotube hybrid having variable ratios of the constituting nanomaterials by employing two different chemical routes to explore their potential in energy storage devices. To study the structure and morphology of synthesized nanomaterials, all samples were characterized by high resolution imaging and spectroscopy techniques. Electrical conductivity of synthesized Graphene-Carbon Nanotube hybrid, graphene oxide and carbon nanotubes was measured by two probe method to study whether the conductivity of hybrid is greater than that of graphene and carbon nanotubes. It was observed that hybrid exhibited excellent stability due to strong π-π interaction between carbon nanotubes and graphene oxide sheets. The maximum electrical conductivity was obtained for the hybrid in which amount of graphene oxide was more than that of multiwalled carbon nanotubes. Moreover, the results of electrical conductivity demonstrated that the structure of hybrid plays significant role in improving its properties.     

碳纳米管/高分子复合材料的制备及应用研究进展

将碳纳米管掺杂到聚合物母体中形成的碳纳米管/高分子复合材料具有良好的力学、导电和非线性光学性质。在聚合物中添加少量碳纳米管可以明显改变聚合物的结晶和形貌。大量研究表明,这些复合材料在诸如太阳能电池、有机发光器件、光限幅、光学开关、防护涂料以及人造肌肉等方面具有潜在的实际应用价值。文中介绍了碳纳米管/高分子复合材料的制备方法及其在高科技领域中的应用潜能。     

Printing Polymer Nanocomposites and Composites in Three Dimensions

Recent advances in materials science and three‐dimensional (3D) printing hold great promises to conceive new classes of multifunctional materials and components for functional devices and products. Various functionalities (e.g., mechanical, electrical, and thermal properties, magnetism) can be offered by the nano‐ and micro‐reinforcements to the non‐functional pure printing materials for the realization of advanced materials and innovative systems. In addition, the ability to print 3D structures in a layer‐by‐layer manner enables manufacturing of highly‐customized complex features and allows an efficient control over the properties of fabricated structures. Here, the authors present a brief overview mainly over the latest progresses in 3D printing of multifunctional polymer nanocomposites and microfiber‐reinforced composites including the benefits, limitations, and potential applications. Only those 3D printing techniques that are compatible with polymer nanocomposites and composites, that is, materials that have already been used as printing materials, are introduced. The very hot topic of 3D printing of thermoplastic composites featuring continuous microfibers is also briefly introduced.     

Modifizierung des ABSE‐Polycarbosilazans mit Multi‐Walled Carbon Nanotubes zur Herstellung spinnfähiger Massen

Modification of the ABSE polycarbosilazane with multi‐walled carbon nanotubes for the creation of spinable masses An inexpensive method has been found to produce ceramic SiCN‐fibres via the precursor route consisting of five processing steps: synthesis of the polymer, preparation of the spinning mass, melt‐spinning, curing via electron beam and subsequent pyrolysis at 1100 °C in a nitrogen atmosphere. A special solid and meltable fibre polymer, the so‐called polycarbosilazane ABSE, has been developed in the last decade for this purpose. Due to its low molecular weight, an adequate catalytic and thermal aftertreatment was necessary to guarantee a stable melt‐spinning process. This article discusses an alternative way to prepare a qualified spinning mass, i.e. the addition of Multi‐Walled Carbon Nanotubes (MWCNTs) to the ABSE melt. For this purpose a homogeneous dispergation of the MWCNTs in the ABSE matrix is necessary. In this study, spinning masses were fabricated in different ways. By optical analysis and comparison of the level of dispergation in these spinning masses an optimized process for integration of the MWCNTs was identified. The influence of the addition of a dispersing agent is investigated as well. In using a dispersing agent, the level of homogeneous dispersion of the MWCNTs increases whereas the interactions between the particles and the precursor melt decrease. In first spinning experiments a good spinability of the masses were noticed. Thus the addition of MWCNTs represents a new way to modify the ABSE precursor for the melt‐spinning process.     

Carbon nanotube–polymer interactions in nanocomposites: A review

The interaction between carbon nanotubes and polymers is critically reviewed. The interfacial characteristics directly influence the efficiency of nanotube reinforcements in improving mechanical, thermal, and electrical properties of the polymer nanocomposite. In this review, various techniques of interaction measurements, including experimental and modelling studies, are described. From the experimental approaches, wetting, spectroscopy and probe microscopy techniques are discussed in detail. Molecular dynamics, coarse grain simulation and density functional theory are also explained as the main modelling approaches in interaction measurement studies. Different methods of interaction improvement, mainly categorized under covalent and noncovalent interactions, are described afterwards. Modelling predictions of nanocomposite properties, such as Young’s modulus, are compared with the experimental results in the literature and the challenges are discussed. Finally, it is concluded that an optimum carbon nanotube–polymer interaction is a key factor towards reaching the full potential of carbon nanotubes in nanocomposites.     

Influence of different carbon nanotubes on the mechanical properties of epoxy matrix composites – A comparative study

Carbon nanotubes (CNTs) in general are considered to be highly potential fillers to improve the material properties of polymers. However, questions concerning the appropriate type of CNTs, e.g., single-wall CNTs (SWCNT), double-wall CNTs (DWCNT) or multi-wall CNTs (MWCNT), and the relevance of a surface functionalisation are still to be answered. This first part of the study focuses on the evaluation of the different types of nanofillers applied, their influence on the mechanical properties of epoxy-based nanocomposites and the relevance of surface functionalisation. The nanocomposites produced exhibited an enhanced strength and stiffness and even more important, a significant increase in fracture toughness (43% at 0.5 wt% amino-functionalised DWCNT). The influence of filler content, the varying dispersibility, the aspect ratio, the specific surface area and an amino-functionalisation on the composite properties are discussed and correlated to the identified micro-mechanical mechanisms.     

Mechanical Reinforcement of Polymers Using Carbon Nanotubes

Owing to their unique mechanical properties, carbon nanotubes are considered to be ideal candidates for polymer reinforcement. However, a large amount of work must be done in order to realize their full potential. Effective processing of nanotubes and polymers to fabricate new ultra‐strong composite materials is still a great challenge. This Review explores the progress that has already been made in the area of mechanical reinforcement of polymers using carbon nanotubes. First, the mechanical properties of carbon nanotubes and the system requirements to maximize reinforcement are discussed. Then, main methods described in the literature to produce and process polymer–nanotube composites are considered and analyzed. After that, mechanical properties of various nanotube–polymer composites prepared by different techniques are critically analyzed and compared. Finally, remaining problems, the achievements so far, and the research that needs to be done in the future are discussed.     

聚合物/碳纳米管复合材料研究进展

聚合物／碳纳米管复合材料近年来引起人们广泛的关注。本文综述了聚合物／碳纳米管复合材料的研究进展，重点介绍了聚合物／碳纳米管复合材料的类型、制备方法及力学、电学和光学性能等。     

Herstellung und Umformverhalten austenitischer Polymerkernsandwichverbunde

Production and forming behaviour of austenitic steel sandwich composites with a polymer core layer Three‐layered symmetrical sandwich combines offer a great lightweight construction potential due to their structural construction and her good recession behavior at simultaneously high strength. By the combinability of the qualities of the combined partners sandwich combines as good solution offer their services if it is about high strength at good resistance in the lightweight construction. Depending on a functional request all sorts of materials, metals, polymer and others, are used as deck and nuclear material. This one is a central problem for the construction, the processing and later use of sandwich systems in comparison with the monolithic materials, terrible forming behaviour of the combined partners with strongly different Youngth Modulus as well as the question of the adhesion of the different material layers. Nowadays the industrial use of such sandwich materials is still limited. In the context of the project “Untersuchungen zur Kompatibilisierungsmethode ”Umformen“ für unterschiedliche Metall ‐ Nichtmetall – Systeme” promoted by the DFG three layered Sandwich materials were manufactured and analyzed for their characteristics concerning the adhesive strength of the sandwich partners and the forming behaviour. The task existed in the development, the production and investigation of new sandwich materials, which can be adapted to special requirements regarding their functional characteristics. Only the combined view of the material and constructional components leads to system‐oriented materials, construction units, concepts and structures. On the basis of an industrially manufacturing process an adapted press‐joining process for sandwich materials was developed. At the beginning of the project polymer foils were used as core materials, then in th developed pres‐joining process different polymers granules were used as core material. Thereby fiber‐reinforced PA and PP granules were used. As skin layers high‐grade steel sheets of the quality 1,4404 and aluminum plates AlMg3 were used. Depending upon manufacturing processes for the polymer foil an epoxy resin adhesive was used and for the polymer granules three different adhesion agents were used. A reproducible manufacturing could be proven by the angle peeling test. The stretching and deep‐drawing characteristics of the sandwich materials as a function of the core layers could be pointed out in the Erichsen‐Test and in first deep‐drawing investigations. So the Youngth Modulus in the comparison to the polymer foil could be increased by fiber‐reinforced polymer granules. It was possible to change the deep‐drawing behaviour clearly.     

Comparison of the thermal properties between composites reinforced by raw and amino-functionalized carbon materials

Carbon materials, such as graphite oxides, carbon nanotubes and graphenes, have exceptional thermal conductivity, which render them excellent candidates as fillers in advanced thermal interface materials for high density electronics. In this paper, these carbon materials were functionalized with 4,4′-diaminodiphenyl sulphone (DDS), to enhance the bonding between the carbon materials and the resin matrix. Their visibly different properties were investigated. It seems that DDS-functionalization can obviously improve the interfacial heat transfer between the carbon materials and the epoxy matrix. The thermal conductivity enhancement of D-Graphene composites (0.493 W/m K) was about 30% higher than that of D-MWNTs composites (0.387 W/m K) at 0.5 vol.% loading. The different effects among EGO, D-EGO, MWNTs, D-MWNTs and D-Graphene in polymer composites were also discussed. It was demonstrated that DDS-functionalized carbon materials had an obvious effect on the thermal performances of composite materials and were more effective in thermal conductivity enhancement.     

Carbon nanotubes for electronics manufacturing and packaging:from growth to integration

Carbon nanotubes (CNTs) possess excellent electrical, thermal and mechanical properties. They are light in weight yet stronger than most of the other materials. They can be made both highly conductive and semi-conductive. They can be made from nano-sized small catalyst particles and extend to tens of millimeters long. Since CNTs emerged as a hot topic in the early 1990s, numerous research efforts have been spent on the study of the various properties of this new material. CNTs have been proposed as alternative materials of potential excellence in a lot of applications such as electronics, chemical sensors, mechanical sensors/actuators and composite materials, etc. This paper reviews the use of CNTs particularly in electronics manufacturing and packaging
field. The progresses of three most important applications, including CNT-based thermal interface materials, CNT-based interconnections and CNT-based cooling devices are reviewed. The growth and post-growth processing of CNTs for specific applications are introduced and the tailoring of CNTs properties, i.e., electrical resistivity, thermal  conductivity and strength, etc., is discussed with regard to specific application requirement. As the semiconductor industry is still driven by the need of getting smaller and faster, CNTs and the related composite systems as emerging new materials are likely to provide the solution to the future challenges as we make more and more complex electronics devices and systems.     

Design of Aligned Carbon Nanotubes Structures Using Structural Mechanics Modeling <br/>Part 1: Theory and Individual Carbon Nanotube Modeling

Aligned carbon nanotubes structures are emerging new materials that have demonstrated superior mechanical, thermal, and electrical properties and have the huge potential for a wide range of applications. In contrast with traditional materials whose microstructures are relatively "fixed", the aligned carbon nanotube materials have highly "tunable" structures. Therefore, it is crucial to have a rational strategy to design and evaluate the architectures and geometric factors to help process the optimal nanotube materials. Astructural mechanics based computational modeling is used for designing the aligned carbon nanotubes structures. Part 1 of the papers presents the theory of the computational method as well as the design and modeling of individual nanotube. As the fundamental building block of the aligned nanotube structures, the variations of geometric parameters of the individual nanotube on its mechanical properties are thoroughly examined.     

Mechanochromic Photonic Gels

Polymer gels are remarkable materials with physical structures that can adapt significantly and quite rapidly with changes in the local environment, such as temperature, light intensity, electrochemistry, and mechanical force. An interesting phenomenon observed in certain polymer gel systems is mechanochromism – a change in color due to a mechanical deformation. Mechanochromic photonic gels are periodically structured gels engineered with a photonic stopband that can be tuned by mechanical forces to reflect specific colors. These materials have potential as mechanochromic sensors because both the mechanical and optical properties are highly tailorable via incorporation of diluents, solvents, nanoparticles, or polymers, or the application of stimuli such as temperature, pH, or electric or strain fields. Recent advances in photonic gels that display strain‐dependent optical properties are discussed. In particular, this discussion focuses primarily on polymer‐based photonic gels that are directly or indirectly fabricated via self‐assembly, as these materials are promising soft material platforms for scalable mechanochromic sensors.     

Assessment of carbon nanotube yarns as reinforcement for composite overwrapped pressure vessels

Carbon nanotubes (CNTs) are one-dimensional nanomaterials with outstanding electrical and thermal conductivities and mechanical properties. Recent advances in CNT manufacturing have made bulk forms such as yarns, tapes and sheets available in commercial quantities to permit the evaluation of these materials for aerospace use. The high tensile properties of CNT composites can be exploited in tension-dominated applications such as composite overwrapped pressure vessels (COPVs). To investigate their utility in this application, aluminum (Al) rings were overwrapped with thermoset/CNT yarn, thermally cured under a vacuum bag, and their mechanical properties measured. Fabrication parameters such as CNT/resin ratio, tension applied during winding, and the number of CNT yarn layers were investigated to determine their effects on the mechanical performance of overwrapped Al rings. Mechanical properties of the CNT composite overwrapped Al rings (CCOARs) were measured under static and cyclic loads at room, elevated, and cryogenic temperatures to evaluate their performance relative to bare Al rings. The ultimate load carried by the composite overwrap in the CCOARs increased with increasing number of wraps. The wet winding process for the CCOAR fabrication improved load transfer compared to the dry winding process due to enhanced interfacial adhesion between the CNT yarn and the applied resin. Wet winding Al rings with CNT yarn/thermoset overwraps resulted in ∼11% increase in weight relative to the bare ring and increased the room temperature breaking load by over 200%.     

Faser‐ und drahtverstärkte Kupferlegierungen als Wärmesenke für Fusionsreaktoren

Fibre and wire reinforced copper alloys as heat sinks for fusion reactors The CuCr1Zr alloy is used in existing experimental fusion reactors and planned to be used as a heat sink in ITER because of his mechanical properties and thermal conductivity (at 20 °C 310–330 W/m/K). Because of aging this dispersion‐hardened alloy is limited in use to temperatures below 450 °C. A possibility to increase the service temperature (the aim is 550 °C) is to reinforce the alloy with SiC‐fibres or W‐wires. With the aid of SiC (SCS‐6) fibres and W‐wires (diameter ～150 μm for both) coated with the CuCr1Zr‐alloy, Cu‐MMCs are produced and their properties (tensile strength, thermal conductivity, fibre/matrix interface properties) are determined. Processing (Hot Isostatic Pressing) causes the alloy to age, making an additional heat treatment necessary in order to optimize the properties. The tensile strength of the different Cu‐MMCs was determined as a function of the volume content of the reinforcements. Tensile strength rises with increasing volume fraction of fibres (or wires) and reaches e.g. 1000 MPa for a SiC‐fibre volume fraction of 24 % or a W‐wire volume fraction of 27 %. Measurements of the thermal conductivity, performed by laser flash, show that the thermal conductivity is reduced with increasing fibre volume fraction (e.g. 200 W/m/K for a fibre volume fraction of 30 %). The W‐wire reinforced CuCr1Zr alloy has been selected because of its better thermal conductivity and interfacial properties to estimate the potential of this Cu‐MMC in a first design study of heat sinks on the basis of different divertor construction types.     

Clay-based polymer nanocomposites: research and commercial development

This paper reviews the recent research and development of clay-based polymer nanocomposites. Clay minerals, due to their unique layered structure, rich intercalation chemistry and availability at low cost, are promising nanoparticle reinforcements for polymers to manufacture low-cost, lightweight and high performance nanocomposites. We introduce briefly the structure, properties and surface modification of clay minerals, followed by the processing and characterization techniques of polymer nanocomposites. The enhanced and novel properties of such nanocomposites are then discussed, including mechanical, thermal, barrier, electrical conductivity, biodegradability among others. In addition, their available commercial and potential applications in automotive, packaging, coating and pigment, electrical materials, and in particular biomedical fields are highlighted. Finally, the challenges for the future are discussed in terms of processing, characterization and the mechanisms governing the behaviour of these advanced materials.     

Strong Anisotropy and Ultralow Percolation Threshold in Multiscale Composites Modified by Carbon Nanotubes Coated Hollow Glass Fiber

Inspired by biological materials, the use of combined fillers of different types and sizes has led to multiscale, hierarchical composites which are considered to be the multifunctional materials of the next generation. However, the effects of hierarchical architecture on the electrical properties and percolation behavior remain poorly understood. Here, a multiscale polymer‐based micro‐/nano‐composite with hollow glass fibers coated by carbon nanotubes (CNTs) has been produced based on a simple dip‐coating approach. Besides a significant increase in electrical performance, the composites exhibit a very strong anisotropy of electrical properties with the difference of 2–5 orders of magnitude in different directions. In the longitudinal direction of composites, an ultralow percolation threshold is found. These unique properties are shown to be related to the hierarchical morphology, which gives rise to the existence of two percolation levels with different thresholds: a local threshold in the nanoscale 2D CNT networks at the fiber‐polymer interfaces and a global threshold in 3D network formed by the fibers. This study helps to deeper understand the macroscopic electrical performance of the hierarchical composites, potentially opening up new ways for designing novel materials via flexible tailoring the orientation of fiber and the morphology of interfaces.

     

Soft Multifunctional Composites and Emulsions with Liquid Metals

Binary mixtures of liquid metal (LM) or low‐melting‐point alloy (LMPA) in an elastomeric or fluidic carrier medium can exhibit unique combinations of electrical, thermal, and mechanical properties. This emerging class of soft multifunctional composites have potential applications in wearable computing, bio‐inspired robotics, and shape‐programmable architectures. The dispersion phase can range from dilute droplets to connected networks that support electrical conductivity. In contrast to deterministically patterned LM microfluidics, LMPA‐ and LM‐embedded elastomer (LMEE) composites are statistically homogenous and exhibit effective bulk properties. Eutectic Ga‐In (EGaIn) and Ga‐In‐Sn (Galinstan) alloys are typically used due to their high conductivity, low viscosity, negligible nontoxicity, and ability to wet to nonmetallic materials. Because they are liquid‐phase, these alloys can alter the electrical and thermal properties of the composite while preserving the mechanics of the surrounding medium. For composites with LMPA inclusions (e.g., Field's metal, Pb‐based solder), mechanical rigidity can be actively tuned with external heating or electrical activation. This progress report, reviews recent experimental and theoretical studies of this emerging class of soft material architectures and identifies current technical challenges and opportunities for further advancement.