摘要:

Model composites of spherical glass particles dispersed in a matrix of high density polyethylene (HDPE) were studied both with and without interfacial modification by an azidofunctional trialkoxysilane. The layer coverage was controlled by varying the amount of silane used for modifying the glass sphere surfaces. The dielectric properties of the silane-modified composites were studied as a function of the water content of the samples after equilibrium water uptake. The amount of absorbed water was controlled via the relative humidity of the environment to which the samples were exposed. Measurements were performed as a function of both temperature between 0°C and 30°C and frequency from 100 mHz to 1 MHz. A dielectric interfacial polarization process due to a water layer adsorbed at the glass filler surface was detected. A theoretical interlayer model for the dielectric properties of particulate-filled composites in which an interfacial interlayer is present is shown to predict the detected dielectric loss process. Owing to the interfacial modification by a silane coupling agent, differences in the dielectric properties and water uptake during the absorption process as well as differences in the temperature dependence of the interfacial loss process between the composites can be detected. These changes can be attributed to the effect of the interfacial modification, and this yields insight into the effect of the silane coupling agent on the water adsorption at the filler-matrix interface.

DOI:10.1163/156855493X00284

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Carbon fibers are a superior reinforcement for composite materials because of their excellent mechanical properties and their low density. A knowledge of the surface of these fibers down to the nanoscale is of great value because the interfacial bonding to the fiber surface has a considerable influence on the mechanical properties of the composite. In this study, the surfaces of as-received carbon fibers were characterized by scanning tunneling microscopy while the surfaces of carbon fibers coated with a silica deposit were observed with an atomic force microscope. In addition, chemical and physical adsorption techniques were used to characterize the global surfaces of the fibers. The data from these various techniques were correlated with silica deposition rate data to produce a model for the nucleation and deposition of silica on carbon fibers.

DOI:10.1163/156855493X00293

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The current understanding of metal-ceramic interactions is presented based on wetting data obtained by the sessile drop technique. The nature of the bonding between metals and ceramics, with emphasis on ionocovalent oxide ceramics, is discussed using an electronic approach. Typical examples are given to illustrate the effect of oxygen on the wetting behaviour of a metal/ceramic system when it acts as a dissolved element in the liquid metal, and when it causes the formation of an oxide film on the metal surface and an oxide-like layer on the ceramic surface. The influence of alloying elements on the wetting properties is elucidated using a thermodynamic model. Following these discussions, the general behaviour of wetting and adhesion in metal/ceramic systems could thus be deduced.

DOI:10.1163/156855493X00301

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A bench-scale continuous fibre treatment line has been built to modify polyethylene fibre surfaces using UV radiation-induced grafting. It is shown that grafting does indeed take place and that the grafts adhere well to the resin. Single-fibre pullout behaviour, interlaminar shear strength, and flexural behaviour were observed to improve considerably. The loss of tensile properties due to treatment was investigated and found to be small in the range of useful treatments. The interlaminar shear strength of the UV-treated fibre is as high as 38 MPa (5.5 ksi) as compared with the untreated fibre value of 10 MPa (1.5 ksi). The most important process parameters are identified and trends established.

DOI:10.1163/156855493X00310

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Alloying the matrix is a convenient and effective way to improve the properties of aluminium matrix composite materials. However, the extent to which the additional elements, such as titanium and copper, would function is not very clear. The aim of this work was to compare the roles played by titanium and copper in carbon fibre-reinforced aluminium matrix composite wires. The kinetics of the interfacial reaction in modelling specimens were studied quantitatively using the depth profile of a scanning auger microprobe. The tensile strength of the composite wires was tested for the specimens in as-fabricated and annealed states, respectively. SEM observations indicated that addition of copper to the aluminium matrix deteriorates the wettability between the matrix and the reinforcements. TEM observations revealed that no significant interfacial reaction took place during fabrication processing, while Al4C3and Ti3AlC formed near the interfaces during annealing. It can be concluded that addition of titanium reduces the interfacial reaction and improves the tensile strength, whereas addition of copper reduces the interfacial reaction but deteriorates the tensile strength slightly.

DOI:10.1163/156855493X00329

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Cellulosic materials have long been used as cost-cutting fillers in the plastic industry. Among the various factors which determine the final performance of the composite materials depend, to a large extent, on the adhesion between the polymer matrix and the reinforcements, and, therefore, on the quality of the interface. In fact, the majority of cellulosic raw materials are lignocellulosics of different polarity to plastics, and due to this divergent behavior, the adhesion between cellulosic materials and polymer matrices is very poor. However, a sufficient degree of interaction or adhesion between the surface of the cellulosic materials and matrix resin is usually desired to achieve an optimum performance of the end-product. In many cases surface modification of the cellulosics or the matrix resins, using various additives, vinyl monomers, or coupling agents, are considered to be essential to achieve this goal. The present paper surveys research work published in this field with special emphasis on the cellulosic materials' surface chemistry, morphology, as well as interfacial properties of the composites in order to elucidate the role of surface treatments. In order to elucidate the mechanism of interaction on molecular level, it is necessary to employ various techniques, such as spectroscopy that can measure surface events. In fact, the complexity of the interphase region requires a variety of characterization methods for the thorough understanding of the physical and chemical nature of this region. Moreover, a proper combination of different techniques is necessary to provide a true picture of the interphase.

DOI:10.1163/156855493X00338

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor