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环氧树脂/聚氨酯梯度聚合物的弯曲性能研究 总被引:1,自引:0,他引:1
考察了不同层数的环氧树脂/聚氨酯(EP/PU)梯度聚合物弯曲性能,采用有限元法分析了材料在弯曲状态下的应力分布,从理论上解释了EP/PU梯度材料弯曲性能的试验结果,并与相同组成的均质材料进行了比较.研究发现:EP/PU梯度材料的弯曲强度和模量随梯度层数的增加而增加,当梯度层数超过5层以后,EP/PU梯度材料的弯曲强度高于相同组成的均质材料.有限元分析结果表明:在EP/PU梯度材料中,应力的分布与各层材料承受的强度相匹配,即应力大的部位材料的强度也越大.梯度层越多,各层之间强度变化越小,应力变化越为缓和,且应力分布与材料强度之间匹配越好,在受外力时,材料断裂强度越高.梯度材料中应力分布方式的理论计算结果很好的解释了实测的各种梯度材料强度变化规律. 相似文献
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功能梯度材料制备方法的研究进展 总被引:2,自引:0,他引:2
功能梯度材料作为一种新型的复合材料,因其优异性能得以广泛应用.本文回顾了功能梯度材料的发展历史,综述了功能梯度材料的制备方法,其中包括粉末冶金法、等离子喷涂技术、粉末冶金法、电沉积法以及气相沉积法等,并提出了今后功能梯度材料的研究重点. 相似文献
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探讨了梯度材料的合成与制备方法的研究进展,提出在非自然环境中制备PMMA梯度折射率材料的制备方法和模型研究。研究表明,增加反应物中两相物质分子或颗粒的作用力差是制备具有应用前景的梯度高聚物材料的关键。并就非自然环境中制备高聚物梯度材料的实验方法、数学模型及利用该方法制备出的高聚物梯度材料的性能表征进行了研究。 相似文献
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梯度功能材料(functionally gradient materials,简称FGM),又常称倾斜功能材料,严格地说应称为”梯度功能复合材料”,本文扼要介绍了用离心法制得的环氧树脂/短碳纤维梯度功能材料的结构及耐磨性能。 相似文献
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组分连续变化的梯度材料的形成技术 总被引:3,自引:0,他引:3
概述了梯度材料的概念和研究的主要内容,着重阐述了梯度材料研究的核心问题--组分连续的梯度材料的形成技术,分析了它们各自的特点,并预估共沉降法是最有希望成为制备组分连续的大型梯度构件的方法。 相似文献
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功能性梯度材料FunctionallyGradientMaterials功能性梯度材料(FGM)是由两种或多种材料复合而成,其组成和结构呈连续梯度变化的一种新型复合材料。最早研究的功能梯度材料是折射率梯度材料,到1969年达到了实用水平。1987年日本平井敏雄等提出使金属和陶瓷复合得到热防护功能性梯度材料的概念。当时日本制订了以开发航天技术用热防护材料为目的的热应力功能梯度的研究计划,引起世界各国的普遍重视。我国在1980年后才开始功能性梯度材料的研究,有关项目均列入国家863计划及国家自然科学基金中,发展较快,进展颇大。一般的复合材料中,其分散… 相似文献
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设计了一种新的梯度组分分布数学模型,采用梯度因子和梯度层数控制梯度组分的分布,并采用逐层浇铸的方法制备了不同层数的EP/PU梯度互穿网络聚合物(IPN)材料;测试了材料的拉伸性能、弯曲性能以及冲击性能;研究了梯度层数变化对这些性能的影响,并同普通IPN的性能进行了对比。研究结果表明,在相同质量比和梯度因子情况下,梯度层数越多,拉伸强度和冲击强度越高,弯曲强度越低。梯度IPN的拉伸强度和冲击强度均高于普通IPN,弯曲强度低于普通IPN。 相似文献
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提出一种新的方法对梯度互穿网络聚合物(IPNs)中梯度组分的分布进行设计,并采用逐层浇注的方法制备了不同层数的环氧树脂/聚氨酯(EP/PUR)IPNs,对其拉伸性能进行了研究。研究结果表明,EP/PUR梯度IPNs的拉伸性能受梯度层数的影响,梯度层数越多,拉伸弹性模量越小,拉伸强度高,但当梯度层数超过7层后,拉伸强度有所降低;EP/PUR梯度IPNs的拉伸性能优于EP和EP/PUR普通IPNs。 相似文献
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In this study, polyethylene (PE)/polystyrene (PS) polymeric gradient material with spatially gradient structure was prepared continuously by a new technique through coextrusion–gradient distribution–two‐dimensional mixing with conventional polymeric material processing facilities. The processing line from coextrusion, gradient distribution to two‐dimensional mixing was fulfilled by two extruders, gradient distribution unit, and two‐dimensional mixing units, respectively. The gradient distribution unit and two‐dimensional mixing units were designed separately in our group. The gradient variation of composition along the sample thickness direction was studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). DSC results indicated that a gradient variation of the content of PE was formed along the sample thickness direction. SEM results showed the direct evolution of morphology of each specimen along the sample thickness direction. The experimental results demonstrated that the processing method with coextrusion–gradient distribution–two‐dimensional mixing can be served as a new way to produce polymer blends with spatially gradient structure and worth to be further investigated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
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目的比较3种不同密度梯度离心方法对脊髓灰质炎病毒空心颗粒、实心颗粒的分离效果。方法选择蔗糖密度梯度离心、氯化铯密度梯度离心、Optiprep(碘克沙醇溶液)密度梯度离心方法,对脊髓灰质炎病毒进行纯化,抽取离心之后的蛋白条带,通过计算蛋白回收率、SDS-PAGE分析、病毒颗粒透射电镜观察,评价其对病毒空心颗粒、实心颗粒的分离效果。结果病毒液经蔗糖、氯化铯和Optiprep 3种介质超速离心,均能分离空心颗粒和实心颗粒。氯化铯密度梯度离心法蛋白回收率优于Optiprep及蔗糖密度梯度离心法;Optiprep密度梯度离心法蛋白纯度优于氯化铯及蔗糖密度梯度离心法。结论通过蛋白回收率、SDS-PAGE分析、病毒颗粒透射电镜观察初步评价了3种方法对脊髓灰质炎病毒空心颗粒和实心颗粒的分离效果,为脊髓灰质炎病毒分离纯化提供了参考。 相似文献
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Shuaiwei Yuan Zhi Yu Peng Wu Shengtai Zhou Huawei Zou Pengbo Liu 《Polymer Engineering and Science》2020,60(9):2292-2300
A series of density gradient polyimide (PI) aerogels were prepared using layer-by-layer assembly and radial freezing method. Briefly, a layer of poly(amic acid) (PAA) ammonium salt aqueous solution was first radially frozen. Then, the second layer of PAA ammonium salt (PAS) aqueous solution of different concentration was added on the top of the first PAS layer and radially frozen. A multilayer gradient PAS solid sample could therefore be fabricated by repeating this similar procedure. The density gradient PI aerogels were obtained after freezing drying and final thermal imidization treatment. Each layer of gradient PI aerogels had anisotropic pore structure, which consisted of tube-like pores along the radial direction and toward the center axis of the cylindrical samples. The compressive strength of five-layer gradient PI aerogel was higher than that of three-layer gradient and single-layer PI aerogels with the same density. The gradient PI aerogels exhibited anisotropic heat transfer behavior in the direction of density gradient, and heat transfer from the higher density side to the lower density side was faster. 相似文献
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Function‐graded proton exchange membranes (G‐PEMs) based on poly(tetrafluoroethylene‐co‐hexafluoropropylene) were fabricated for direct methanol fuel cells (DMFCs) via electron beam‐grafting using the heterogeneous energy deposition technique. The G‐PEMs had a water uptake gradient in the proton transfer direction, originating from the sulfonic acid group gradient. The distribution of sulfonic acid groups in the various G‐PEMs was evaluated using X‐ray photoelectron spectroscopy. Four types of PEMs (flat‐type, strong‐gradient, meso‐gradient, and weak‐gradient types) were fabricated. By varying the direction of the G‐PEMs, the methanol permeation test and DMFC operation were performed with two orientations of the sulfonic acid group gradient, decreasing from the methanol injection (anode) side (decrease‐type) or the other (cathode) side (increase‐type). The methanol permeability of the strong‐gradient, meso‐gradient, and weak‐gradient G‐PEMs was lower than that of Nafion®117 and the flat‐type PEM. The “increase‐type” orientation of the strong‐gradient G‐PEM resulted in the lowest methanol permeability. The DMFC performance of the G‐PEMs was influenced by the thickness direction, such as “decrease‐type” and “increase‐type.” The performance of the “decrease‐type” assembly was higher than that of the “increase‐type.” The “decrease‐type” assembly with P‐200 k (weak‐gradient G‐PEM) exhibited the highest performance of the fabricated PEMs, comparable to that of Nafion®117. 相似文献
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通过控制不同单体的加料速度,采取递变加料的方式,合成了具有类似“洋葱”结构的梯度乳液聚合物,并对影响聚合物梯度结构的相关因素进行了探讨,测试了梯度乳液聚合物成膜后豹力学性能。实验发现,加料速度和乳化剂的用量都会影响到聚合物梯度构造的形成,梯度聚合物的成膜物在抗拉伸强度和断裂伸长率方面都有不错的表现,具备良好的力学性能。 相似文献