摘要:

Conductive composites based on PE, PP, PS, PMMA and PA filled with carbon black have been studied. It was found that percolation behavior of the conductivity depended on the degree of polymer-filler interaction. Equations taking into account the polymer-filler interactions were proposed to describe the conductivity of composite above and below the percolation threshold.

DOI:10.1163/156855497X00145

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The modified null field approach to elastic P- and SV-wave scattering (in plane strain) from a partially debonded fiber has been developed. The debonded region on the fiber surface is subjected to traction free boundary conditions, whereas the fiber is assumed to be in welded contact with the host medium elsewhere. Additional null field equations for an elliptical extension of the actual surface of the scatterer are introduced which require additional expansions for the field in the region between the extended mathematical boundary and the actual boundary of the scatterer. The numerical accuracy of the modified null field method has been tested for the case of a perfectly bonded fiber for P- and SV-wave incidence. Scattering cross-section plots are presented for different degrees of debonding.

DOI:10.1163/156855497X00154

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The experimental technique of single-fiber electromechanical pull-out testing was introduced and used to study the interface between steel fiber and cement. The technique involves measuring both the contact electrical resistivity between fiber and matrix and the shear bond strength in a fiber-matrix interface sample. Samples that are identically prepared differ in contact resistivity and bond strength, which correlate. The correlation allows determination of even small differences in bond strength due to differences in sample preparation conditions, such as fiber surface treatment, cement curing age and admixtures to the cement paste. It also gives information on the structure of the interface and allows the bond strength to be non-destructively determined by measuring the contact resistivity.

DOI:10.1163/156855497X00163

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Thermal and thermochemical treatments with amines have been shown to improve both the mechanical strengths of carbon fibers and their interfacial bonding forces with polymer matrix. In this report, the wettabilities of the surface-treated carbon fibers were studied by dynamic contact angles with epoxy resin. Two mechanisms occur during the fiber modification processes, namely, the fiber core restructuring and surface etching. The former occurs at elevated temperature and increases the fiber strength significantly. When surface reaction occurs, the number of surface oxides increases to improve the surface wettabilities, which may be observed by the decreased dynamic contact angles. Accompanying the etch-cleaning effects, the fiber strength would also increase initially. Deeper penetration of amine would destroy the graphite crystallinity on fiber surfaces and lower the fiber strength.

DOI:10.1163/156855497X00172

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Enhancement of a flexible poly(vinyl chloride) (PVC)-silica composite interface was studied by the application of γ-aminopropyltrimethoxysilane on silica. Composites containing silica and silanized silica up to 25.6 phr (per hundred resin) and prepared by sol-gel technology were subjected to water and water vapor attacks similar to that in their daily use. Silane application resulted in diminishing liquid water and water vapor sorption by about 24.0% and 11.9%, respectively. Equilibrium weight gain values of the composites having different amounts of silica correlated well with a peak at 3400 cm-1in the IR spectra which was attributed to the stretching vibration of the O-H group of water. Liquid water and water vapor diffusivities in composites determined by the evaluation of weight gain against time data were about 0.4 x 10-13and 0.4 x 10-12m2s-1, respectively. Inhibition of dioctyl phthalate (DOP) migration from composites by silane application was also determined as 24% using UV measurements. The most impressive merit of silane enhancement was observed as the retention of ultimate tensile strength (UTS) under wet conditions. While the untreated silica composite reduced its UTS by about 21.2%, silanized silica composite reduced its UTS by only about 13.6%, on wetting.

DOI:10.1163/156855497X00181

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor