表面改性和复合工艺对金属纤维/聚合物复合材料性能的影响

以不锈钢纤维为导电填料,分别与ABS和PP复合,制得了电磁屏蔽用导电高分子复合材料。考察了表面改性和复合工艺对金属纤维／聚合物复合材料性能的影响。结果表明,用不同表面处理剂处理不锈钢纤维后,随纤维表面张力增加,复合材料的电阻率增加。使用母料法工艺可以有效地改善金属纤维在聚合物基体中的分散,从而提高复合材料的导电性能和电磁屏蔽性能。     

镀铜／镍聚丙烯腈纤维填充复合材料电磁波屏蔽性能的研究

研究了镀铜／镍的聚丙烯腈纤维填充ＡＢＳ树脂制得的复合材料的导电性及电磁波屏蔽性能，复合材料的导电性主要与导电纤维的填加量有关，导电纤维与基体树脂间的相容状况、复合加工时某些工艺条件等对复合材料的导电性也有较大的影响，电磁波屏蔽性能随导电纤维填加量的增加而提高，加入适当的偶联剂有助于改善和复合材料的电磁波屏蔽性能。     

镀金属玻璃纤维/ABS树脂复合材料制备及电磁屏蔽性能研究

通过热浸镀及化学镀方法制备了玻璃纤维/Al、玻璃纤维/Ni及玻璃纤维/Ni/Ni-Cu-P三种镀金属纤维,对其制备工艺、机理和性能进行了探讨.用上述三种金属化纤维与ABS树脂共混制备出导电复合材料,对复合材料的导电性及电磁屏蔽性能进行了初步研究.     

CF／ABS树脂复合材料制备工艺对导电性能的影响及对屏蔽性能的理论预测

本文研究了使用溶剂法、密炼机和开炼机混炼碳纤维填充ＡＢＳ树脂复合材料的导电性能，得到了纤维填充量与复合材料电阻率的关系，对其导电机理进行了分析。通过比较，发现纤维长径比是决定复合材料导电性能的重要因素，其它如纤维在基体中的分布也对复合材料导电性能有影响。最后对复合材料的屏蔽性能进行了理论计算。     

金属纤维填充聚合物复合材料的导电性能和电磁屏蔽性能

以不锈钢纤维作为填料,分别与ＡＢＳ和ＰＰ两种聚合物复合制得了电磁屏蔽用导电性高分子复合材料。通过研究复合材料导电性能和电磁屏蔽性能与纤维含量的关系,发现结晶性的ＰＰ基体比无定形ＡＢＳ基体所需的纤维临界填充量低,同时ＳＳＦ／ＰＰ的屏蔽效果高于ＳＳＦ／ＡＢＳ复合材料;此外,结果还表明这类复合材料对电磁波的屏蔽效果以吸收损耗为主,反射损耗量较小。     

不同陶瓷颗粒增强Cu基复合材料的制备及导电性能

以纯铜为基体,以WC、AlN、TiN、MgB2等具有不同导电性能与密度的陶瓷颗粒为增强相,采用球磨-冷压-烧结工艺制备了WCp/Cu、AlNp/Cu、TiNp/Cu和MgB2p/Cu系列复合材料.研究了制备工艺的不同环节对铜基复合材料导电性能的影响,讨论了不同陶瓷颗粒增强铜基复合材料的导电性能.结果表明相同制备工艺及体积分数条件下,以具有不同导电性能与密度的陶瓷颗粒作为增强相的铜基复合材料的导电性能相近,球磨、冷压、烧结、复压及复烧等工艺环节对铜基复合材料导电性能有不同程度的影响,提高铜基复合材料的致密度为提高其导电性能的关键.     

颗粒种类及制备工艺对铜基材料性能影响

以纯铜为基体,以WC、AlN、TiN、MgB2等具有不同导电性能与密度的陶瓷颗粒为增强相,采用粉末冶金工艺制备了WCp/Cu、AlNp/Cu、TiNp/Cu和MgB2p/Cu系列复合材料.研究了不同增强颗粒、制备工艺的不同环节对铜基复合材料导电性能的影响.结果表明:相同制备工艺及体积分数条件下,以具有不同导电性能与密度的陶瓷颗粒作为增强相的铜基复合材料的导电性能相近,混粉、压制、烧结、复压及复烧等工艺环节对铜基复合材料导电性能有不同程度的影响,提高铜基复合材料的致密度为提高其导电性能的关键.     

CF/ABS树脂复合材料制备工艺对导电性能的影响及对屏蔽性能的理论预测

本文研究了使用溶剂法、密炼机和开炼机混炼碳纤维填充ABS树脂复合材料的导电性能,得到了纤维填充量与复合材料电阻率的关系,对其导电机理进行了分析.通过比较,发现纤维长径比是决定复合材料导电性能的重要因素,其它如纤维在基体中的分布也对复合材料导电性能有影响.最后对复合材料的屏蔽性能进行了理论计算.     

铜系复合涂料的制备及导电性能

采用醇酸树脂为基料 ,金属铜粉和金属纤维为导电填料以及溶剂和助剂 ,研制成电磁屏蔽导电涂料 ;讨论了铜粉和金属纤维的含量以及固化工艺对涂料导电性能的影响 ,并通过涂层的导电机理 ,探讨了造成这些影响的原因     

聚苯胺／维尼纶导电复合纤维的制备与性能

采用简便的化学氧化现场吸附聚合法制得了聚苯胺／维尼纶导电复合纤维，并研究了制备条件对其性能的影响。该导电复合纤维具有较好的导电性及力学性能，并在空气中很高的稳定性，其电导率可达１０＾－２Ｓ／ｃｍ数量级。采用扫描电镜（ＳＥＭ）对该导电复合纤维的微观结构进行了观察。     

Graphite-fibre/carbide-matrix composites—II: Structure and electrical properties

The measurement of electrical properties of ceramic-matrix composites supplies data which can be used directly with information about the structure of the composites. The structures of graphite-fibre/carbide-matrix composites may be varied within large intervals of appropriate parameters, as shown in a previous publication. A corresponding variety of behaviour patterns of such materials in the electrical field had been expected and was actually observed. The matrices of the composites were boron, niobium, and tantalum carbides, and the fibres were Kulon and VMN-4. The electrical conductivity of graphite-fibre/carbide-matrix composites has been determined, including that at cryogenic temperatures. A preliminary series of experiments gives the characteristics of piezo-resistance of the C/NbC composites. The experimental data yield a set of characteristics of the fibre, matrix, and composite structure. The conductivity characteristics of the graphite fibres and carbide matrices obtained in this way correspond to the expected ones. That also includes a type of conductivity behaviour revealed by the temperature dependence of the conductivity. Graphite fibre behaviour is of the metallic type, while boron carbide is a semiconductor-type material. The conductivity of pure matrices differs essentially from that of the matrices obtained as an extrapolation of the conductivity versus fibre volume fraction dependence to zero fibre content. Active diffusion of carbon from the fibre/matrix interface makes the stoichiometry of a carbide better and its conductivity higher. But a distinctive dependence of the piezo-resistance of the C/NbC composites on the fibre volume fraction may lead to an assumption about the possibility of the existence of another mode of influence of the carbon fibres on the conductive properties of carbides. Calculation of the ineffective length of a fibre (from the viewpoint of conductivity) yields an estimate of the conductivity of the interface. It is clearly connected to the structure of the interface.     

Electrical percolation phenomena in cement composites containing conductive fibres

Electrical conductivity measurements on cement composites containing carbon fibres or steel fibres were conducted. Percolation phenomena associated with electrical conductivity were observed. The conductivity of the systems studied increased by several orders of magnitude, at a specific concentration of conductive fibre, i.e. the percolation concentration. The percolation concentration is shown to be dependent on conductive fibre geometry instead of system composition. The results provide an important guide for the manufacture of conductive cement composites containing conductive fibres.     

The matrix fatigue behaviour of fibre composites subjected to repeated tensile loads

In a fibre/metal matrix composite the mechanical properties of the matrix itself are changed by the presence of the reinforcing fibres. This changed behaviour of the metal is referred to asin situ behaviour, and a phenomenological model is developed to evaluate thein situ plastic stress-strain properties of a metallic matrix containing fibres, from a study of the properties of the composite. The model is based upon the idealised behaviour of the two components of the system. The application of the model to B/Al alloy composites shows that the plastic stress-strain behaviour of the matrix containing fibres varies strongly with the fibre volume content, and also that the matrixin situ cyclic stress-strain behaviour can be approximately described by a power law of the type: where the strength coefficient and the exponent increase with the fibre volume fraction. It also predicts that in the steady state fatigue behaviour of the composites, the fraction of load amplitude carried by the fibres decreases with increasing applied stress amplitude, and is also dependent on the fibre volume fraction. The effect of the applied stress on the damping capacity is established through expressions derived from the basic ideas involved in the model.     

Strain-sensitive Raman spectroscopy and electrical resistance of carbon nanotube-coated glass fibre sensors

This paper presents the development of glass fibres coated with nanocomposites consisting of carbon nanotubes (CNTs) and epoxy. Single glass fibres with different CNT content coating are embedded in a polymer matrix as a strain sensor for composite structures. Raman spectroscopy and electrical response of glass fibres under mechanical load are coupled for in situ sensing of deformation in composites. The results show that the fibres with nanocomposite coating exhibit efficient stress transfer across the fibre/matrix interface, and these with a higher CNT content are more prone to fibre fragmentation at the same matrix strain. A relationship between the fibre stress and the change in electrical resistance against the fibre strain is established. The major finding of this study has a practical implication in that the fibres with nanocomposite coating can serve as a sensor to monitor the deformation and damage process in composites.     

Mechanical and electrical performance of Roystonea regia/glass fibre reinforced epoxy hybrid composites

The present paper investigates mechanical and electrical properties of Roystonea regia/glass fibre reinforced epoxy hybrid composites. Five varieties of hybrid composites have been prepared by varying the glass fibre loading. Roystonea regia (royal palm), a natural fibre was collected from the foliage of locally available royal palm tree through the process of water retting and mechanical extraction. Roystonea regia, E-glass short fibres were used together as reinforcement in epoxy matrix to form hybrid composites. It has been observed that tensile, flexural, impact and hardness properties of hybrid composites considerably increased with increase in glass fibre loading. But electrical conductivity and dielectric constant values decreased with increase in glass fibre content in the hybrid composites at all frequencies. Scanning electron microscopy of fractured hybrid composites has been carried out to study the fibre matrix adhesion.     

镀镍炭毡复合材料的微波吸收特性

用玻璃纤维、镀镍炭毡和高导电性镀镍炭纤维与环氧树脂复合制备了三层结构复合材料证明了镀镍碳毡的吸波性能与镍含量有关；在适当的设计条件下，辅之以少量的炭黑、铁氧体添加剂，可获得较为理想的微波吸收特性     

Plasma surface modification of advanced organic fibres

The interlaminar shear strength, interlaminar fracture energy, flexural strength and modulus of extended-chain polyethylene/epoxy composites are improved substantially when the fibres are pretreated in an ammonia plasma to introduce amine groups on to the fibre surface. These property changes are examined in terms of the microscopic properties of the fibre/matrix interface. Fracture surface micrographs show clean interfacial tensile and shear fracture in composites made from untreated fibres, indicative of a weak interfacial bond. In contrast, fracture surfaces of composites made from ammonia plasma-treated fibres exhibit fibre fibrillation and internal shear failure as well as matrix cracking, suggesting stronger fibre/matrix bonding, in accord with the observed increase in interlaminar fracture energy and shear strength. Failure of flexural test specimens occurs exclusively in compression, and the enhanced flexural strength and modulus of composites containing plasma-treated fibres result mainly from reduced compressive fibre buckling and debonding due to stronger interfacial bonding. Fibre treatment by ammonia plasma also causes an appreciable loss in the transverse ballistic impact properties of the composite, in accord with a higher fibre/matrix interfacial bond strength.     

Microwave absorbent: preparation,mechanical properties and r.f.-microwave conductivity of SiC (and/or mullite) fibre reinforced Nasicon matrix composites

The electrical and mechanical properties of composites made with Nicalon® NLM202 SiC (and Nextel® 440) woven fibres in a sol-gel prepared Nasicon matrix are reported. Local microhardness, interfacial shear stress and three point flexural strength have been determined and correlated to the conclusion of an X-ray microanalysis of the fibre-matrix interphases. The radio frequency (r.f.) to microwave conductivity of the composites has been measured and compared with that of their constituents (Nasicon matrix, SiC fibre) and with the direct current (d.c.) conductivity of extracted fibres.     

Observations on the electrical resistivity of steel fibre reinforced concrete

Steel fibre reinforced concrete (SFRC) is in many ways a well-known construction material, and its use has gradually increased over the last decades. The mechanical properties of SFRC are well described based on the theories of fracture mechanics. However, knowledge on other material properties, including the electrical resistivity, is sparse. Among others, the electrical resistivity of concrete has an effect on the corrosion process of possible embedded bar reinforcement and transfer of stray current. The present paper provides experimental results concerning the influence of the fibre volume fraction and the moisture content of the SFRC on its electrical resistivity. The electrical resistivity was measured by alternating current (AC) at 126 Hz. Moreover, an analytical model for the prediction of the electrical resistivity of SFRC is presented. The analytical model is capable of predicting the observed correlation between the fibre volume fraction and the electrical resistivity of the composite (the SFRC) for conductive fibres and moisture saturated concrete. This indicates that the steel fibres were conducting when measuring the electrical resistivity by AC at 126 Hz. For partly saturated concrete the model underestimated the influence of the addition of fibres. The results indicate that the addition of steel fibres reduce the electrical resistivity of concrete if the fibres are conductive. This represents a hypothetical case where all fibres are depassivated (corroding) which was created to obtain a conservative estimate on the influence of fibres on the electrical resistivity of concrete. It was observed that within typical ranges of variation the influence of the moisture content on the electrical resistivity was larger than the effect of addition of conductive steel fibres, but also that the relative impact on the electrical resistivity due to conductive steel fibres increased when the moisture content of the concrete was reduced.