共查询到20条相似文献,搜索用时 15 毫秒
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The melt-state viscoelastic properties of exfoliated in?situ polymerized and intercalated solution-blended polystyrene (PS) and organically modified montmorillonite nanocomposites were investigated and compared. The PS nanocomposites prepared by nitroxide-mediated polymerization (NMP) exhibit a stable exfoliated structure whereas the PS nanocomposites prepared by solution mixing exhibit an intercalated structure. The linear viscoelastic properties were strongly correlated with the dispersion state of the nanocomposites. On the other hand, the non-linear oscillatory shear properties exhibited shear thinning character and were consistent with the weak interactions between the polymer and the layered silicate. 相似文献
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Sara Bressi Alan Carter Nicolas Bueche André-Gilles Dumont 《International Journal of Pavement Engineering》2016,17(5):403-413
This paper evaluates the variability of binder rheology for different ageing levels and the influence of ageing at different testing temperatures. Three different ageing levels were applied on a single type of bitumen with a penetration grade of 70/100.The artificial ageing of the binder was performed using the rolling thin-film oven test and the pressure ageing vessel. The rheological behaviour was investigated at low temperatures with the bending beam rheometer (BBR) and at medium and high temperatures with the dynamic shear rheometer (DSR). Several experiments were conducted to determine the range of stiffness and complex modulus results, the type of distribution comparing real and theoretical models, and the effects of ageing on the variability of the rheological behaviour. It was shown that not only the mean results from BBR and DSR tests change with ageing, but also the variability of the results changes with ageing. This would have an impact on mechanistic-empirical pavement design because it would influence the calculated stresses and strains as well as the calculated reliability. 相似文献
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基于热压罐成型工艺, 选择了树脂柱Z向增强泡沫芯材、碳纤维Z向增强泡沫芯材、Kevlar纤维缝纫增强泡沫芯材3种Z向增强复合材料结构, 对夹芯结构进行了低速冲击损伤和冲击后压缩(CAI)性能研究, 考察了不同Z向增强方式对冲击损伤面积和破坏模式的影响。结果表明, Z向增强对泡沫芯材产生了初始损伤, 其冲击后损伤面积大于未增强泡沫夹芯结构; 但Z向增强改变了夹芯结构的压缩破坏机制。通过选用合适的Z向增强材料和Z向增强参数, 能够提高夹芯结构的压缩强度和CAI强度。其中当增强材料为碳纤维, 增强参数为10 mm×10 mm时, 压缩强度提高了13%, CAI强度提高超过40%。 相似文献
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C. Pozrikidis 《Journal of Engineering Mathematics》2001,41(2-3):237-258
The simple shear flow of ordered and random, non-dilute and concentrated emulsions resembling foam is considered in the presence of an insoluble surfactant. Numerical investigations conducted by the method of interfacial dynamics for Stokes flow combined with an implicit finite-volume method for computing the evolution of the surfactant concentration illustrate the effect of the surfactant on the rheological properties of the emulsion and on the dynamics and stability of the evolving microstructure. Studies of ordered two-dimensional systems, where the suspended phase is distributed on an evolving doubly-periodic lattice, show that, depending on the capillary number, a surfactant may either destabilize or stabilize a concentrated emulsion by promoting or preventing the rupture of thin films developing between the interfaces of adjacent drops. The capillary number, viscosity ratio, and surfactant diffusivity are found to play an important role in determining the rheological properties of the emulsion and the geometrical properties of the evolving microstructure. Large-scale numerical simulations of random two-dimensional systems with 25 drops suspended in a doubly-periodic flow suggest that the qualitative effect of a surfactant is not altered by strong hydrodynamic interactions associated with intercepting or clustering drops. 相似文献
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Gary Burgess 《Packaging Technology and Science》1999,12(3):101-104
Convoluted polyurethane foam was tested for its cushioning ability in controlled drop tests using a cushion tester. The purpose of the tests was to relate the peak acceleration transmitted to the falling weight to key geometric features of the cushion, such as base thickness and area, along with finger height and spacing. It was found that the fingers had the effect of reducing the impact velocity in a predictable manner, allowing the convoluted cushion to be treated as a block design so that published cushion curves for the same material could be used to obtain the peak acceleration. In effect, convoluted foam behaves like a block cushion of the size of its own base in a drop from a reduced height, the reduction being several times the finger height. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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The objectives of this study were to apply fabrication techniques for the zein montmorillonite (MMT) nanocomposite films and
characterize the obtained nanocomposite films. Zein MMT nanocomposite films were successfully produced from solvent casting
and blown extrusion methods. The two methods could mix the zein MMT resulting in partially exfoliated nanocomposite structures
according to X-ray diffraction and transmission electron microscopy. The thermal resistant of the zein nanocomposite films
fabricated from both methods improved as the MMT content increased. However, the mechanical and barrier properties showed
non-linear relationships with the MMT loadings. The impact of MMT on properties of zein films strongly depended on the preparation
techniques. This can be the good starting point to further study in depth insight of the controllable MMT rearrangement in
zein films which will remarkably improve zein film properties for packaging applications. 相似文献
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为改善玉米醇溶蛋白(Zein)的拉伸性能,本文以竹粉为原料制备生物炭,以球磨后的生物炭(0.536 μm)、竹纤维(2.157 μm)为增强相,以Zein为连续相,利用溶液浇注法制备复合膜材料,并对复合膜材料的基本特性与拉伸性能进行了研究。结果表明,生物炭与竹纤维加入没有改变Zein的晶面结构,提高了Zein的无序性,降低了Zein的脆性,提高了Zein的韧性。生物炭的加入降低了竹纤维/Zein复合膜的亲水性,降低了竹纤维/Zein复合膜的热稳定性,改善了竹纤维/Zein复合膜的拉伸性能。相比而言,添加0.2 g竹纤维、0.1 g生物炭的Zein复合膜材料的拉伸性能最佳,其拉伸强度、拉伸模量、断裂伸长率分别为0.24 MPa、4.17 MPa、327.27%。本文制备的复合膜材料具有较好的拉伸性能,在包装膜材料领域具有一定的应用潜力。 相似文献
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K. Ramamurthy E.K. Kunhanandan Nambiar G. Indu Siva Ranjani 《Cement and Concrete Composites》2009,31(6):388-396
Though foam concrete was initially envisaged as a void filling and insulation material, there have been renewed interest in its structural characteristics in view of its lighter weight, savings in material and potential for large scale utilization of wastes like fly ash. The focus of this paper is to classify literature on foam concrete in terms of constituent materials (foaming agent, cement and other fillers used), mix proportioning, production methods, fresh and hardened properties of foam concrete. Based on the review, the following research needs have been identified: (i) developing affordable foaming agent and foam generator, (ii) investigation on compatibility between foaming agent and chemical admixtures, use of lightweight coarse aggregate and reinforcement including fibers, (iii) durability studies, and (iv) factors influencing foam concrete production viz., mixing, transporting and pumping. 相似文献
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Thermal properties of polyimide foam composites 总被引:1,自引:0,他引:1
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In this research, a triaxial shear test is used as a means to provide yield surface data as well as other strength characteristics
for carbon microballoon (CMB) syntactic foam. Additionally, pure shear tests and tensile tests are used to probe areas of
this stress space not included in the triaxial shear tests. The data are used to characterize the material’s yield strength
in stress space. The determined yield surface, the strain and other deformational behavior characteristics provide the necessary
information for an accurate model and engineering design. The CMB foam specimens were divided into two sets: one with Thornel
pitch-based carbon fibers and one without; both use Kerimid 601 as the binder. The CMB syntactic foam with fibers exhibited
lower shear strength than the CMB syntactic foam without fibers. This is evident not only in the determined shear envelopes
but also in the values obtained for the hydrostatic yield of both foams. Complementary analysis of the blending process of
mixing fibers with CMB has been shown to destroy the microballoons and thus reduce the foams strength. The consequences of
incorporating alternative materials can be verified with further testing. 相似文献
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Kuo Chen Xiuhua LiDongsheng Lv Fangyun YuZheng’e Yin Tao Wu 《Materials Science and Engineering: B》2011,176(15):1239-1242
Materials with the properties of electromagnetic (EM) wave absorption are attractive topics. In this work, we report that EM wave absorption composites, consisting of foam glass, zinc and zinc oxide, were prepared by sintering mixture of foam glass raw material and zinc powder. Microwave reflection loss of composite was calculated based on the permittivity in the range of 8.2-12.4 GHz. The results show that zinc-containing foam glass absorbs efficiently microwaves. The sample with zinc filler to foam glass mass ratio of 3/18 had a reflection loss below −10 dB in the range of 11.3-12.4 GHz, and the minimum reflectivity was −15.6 dB at both 12.0 and 12.4 GHz. Microwave absorption performances of specimens can be controlled by changing the ratio between zinc powder and foam glass mass. The detailed mechanism of the control was investigated through X-ray diffraction (XRD) analysis and scanning electrical microscopy (SEM) observations. 相似文献
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M. L. Addonizio L. D’orazio C. Mancarella E. Martuscelli A. Casale A. Filippi 《Journal of Materials Science》1989,24(8):2939-2950
A study of the rheological behaviour of polyamide 6 (PA6) and PA6/ethylene-vinyl acetate copolymers (EVA) blends in the molten
state is reported. Zero shear viscosity, η0, and the activation energy for the viscous flow, ΔE
*, were obtained as functions of both composition and molar mass of the components. The mode and state of dispersion of the
minor components in samples of extruded blends were extensively analysed and correlated with molecular characteristics and
chemical structure of the EVA copolymers. 相似文献
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制备了泡沫铝、泡沫铝-环氧树脂及含有不同体积分数空心玻璃微珠(HGM)的三种泡沫铝-HGM/环氧泡沫互穿相复合材料(IPC).通过一系列准静态压缩实验,观察了其变形形貌,研究了其弹性模量、屈服极限、比强度及比刚度等力学性能与HGM体积分数的关系.通过三点弯曲实验,研究了IPC的弯曲极限载荷、弯曲弹性模量等性能,分析了其断口形貌与材料结构的关系.实验结果表明:四种IPC的力学性能均较纯泡沫铝有大幅度的提高,其中,泡沫铝-环氧树脂的压缩和弯曲力学性能最好.随着复合材料中HGM体积分数增加,IPC力学性能逐渐缓慢降低. 相似文献
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《Cement and Concrete Composites》2006,28(5):475-480
Most of the investigations on foam concrete in the past have been confined to neat cement paste, cement paste with partial replacement with admixtures and to cement–sand mixes. This paper reports the results of a systematic study to ascertain the influence of filler type (i.e., sand and fly ash) and the particle size of sand on the properties of moist cured foam concrete. This study shows that the consistency of mixture, for achieving pre-formed foam concrete of design density, mainly depends on the filler type. The flow behaviour of foam concrete is mainly influenced by the foam volume. A reduction in particle size of sand caused an improvement in strength of foam concrete. For a given density, replacement of sand with fly ash resulted in higher strength. Finer filler resulted in a higher ratio of strength to density. 相似文献
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《Cement and Concrete Composites》2005,27(1):41-47
Crumbled recycled foam polystyrene waste as well as spherical large and fine blown polystyrene waste is used to produce the filler for a light thermo-insulating composite, the matrix of which is light foam cement. For better cohesion, fillers are hydrophilizated with foam cement surfactant solution.Polystyrene granules and foam cement concrete interaction schemes are discussed. The investigation of foam cement concrete and polystyrene granule contact zone showed that the contact of these two materials is very close, without any fractures or microcracks. Adherence of the two components depends on the size and shape of granules used.When a polystyrene granule is ripped out of foam cement concrete, the emerged “hole” closely repeats the structure of the granule and there is some polystyrene residue left in it. This proves the fact that foam cement concrete contact zone is stronger than the polystyrene granule material. When fine polystyrene granules are used, it disintegrates along the contact zone. Such composite has the lowest adhesion strength, however, it is stronger in comparison with a composite, made with different foam polystyrene granules, provided by better macrostructure. Strength and thermal conductivity of the composite depend on its density, the filler, its sort and amount used, and is defined by regression equations. 相似文献
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Through-thickness stitched foam core sandwich composites were fabricated by using RTM process; and impact performance and damage extent were studied at 1–70 J impact energy levels. The results show that two sharp peak loads and a low-loading plateau appear on the load-time plots at 1–30 J impact energy levels; both sharp peak loads can be considered as the course of penetrating top and bottom facings, a low-loading plateau has the characteristics of penetrating foam cores. Compare to the unstitched samples, the average damage angle of stitched samples increase by 48%, the maximal cracking width and penetration depth of the stitched samples decrease by 67% and 4% at 25 J impact energy levels. 相似文献