摘要:

The fiber-matrix adhesion mechanism in high modulus pitch-based carbon fiber-epoxy matrix composites has been studied. The surface morphology and chemistry of the carbon fibers were examined by microscopic (SEM, STM), thermodynamic and spectroscopic (XPS, Raman) techniques. The interlaminar shear strength and transverse tensile strength of the composites made from surface-treated and untreated fibers were also obtained. In the microscopic analysis, there was no difference in the surface roughness between the surface-treated and untreated fibers. In the thermodynamic and spectroscopic analyses, surface treatment of the carbon fibers increased the amount of surface oxygen. The results indicated that the major role of the surface treatment on the carbon fiber-epoxy resin adhesion is not the mechanical interlocking effect by the surface roughness. The formation of surface oxygen-containing functional groups is assumed to account for the increase in fiber-matrix interfacial adhesion.

DOI:10.1163/156855493X00013

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Three distinct types of metal-ceramic interfaces are summarized. The nature of the bonding, problems in quantifying wettability, the thermodynamic driving force for interface formation, and certain aspects of interfacial stability are discussed with the help of examples. The surface wetting model developed previously by the authors is also discussed.

DOI:10.1163/156855493X00022

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Ultra-high modulus polyethylene (UHMPE) fibres have been treated using a novel 'non-plasma' treatment allowing the incorporation of various chemical functional groups onto the polymer surface. The process comprises two steps: corona discharge treatment, followed by silanization of the polymer surface by a solution of an organo-functional silane. Corona discharge treatment incorporates oxygen-containing functionalities, e.g. reactive hydroxyl groups, onto the polymer surface. The presence of reactive -OH groups provides the possibility of covalent linkage of any organo-functional silane to the corona discharge-treated polymer in the form of a fibre, film, sheet, or powder. The effectiveness of the process was assessed by examining the interlaminar fracture energy and flexural modulus and by SEM analysis of the fracture surfaces of composites fabricated from the untreated, corona discharge-treated, ammonia plasma-treated, and the amine-grafted (using the novel process) UHMPE fabric. A significant improvement in interfacial adhesion was confirmed by increases in the interlaminar fracture energies and flexural moduli. The effectiveness of the process investigated is similar to the ammonia plasma treatment. SEM analysis of the fracture surfaces indicated a change in the fracture mode from purely adhesive for unmodified fibres, through to mixed failure mode for corona-treated material, to highly cohesive-in-fibre surface for amine-grafted UHMPE fibres. XPS analysis confirmed the incorporation of the amine groups onto the surface of polyethylene treated using the novel method.

DOI:10.1163/156855493X00031

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The stress field arising in the single fiber pull-out test is analysed within the framework of the linear theory of elasticity by means of the finite element method, utilizing an idealized model. The finite element analysis is compared with the frequently employed shear lag theory. It is shown that the stress distribution in the vicinity of the fiber is extremely inhomogeneous with strong concentrations in the boundary layer, at the matrix surface as well as at the fiber end, which are not predicted by the shear lag theory. The influence of the fiber length to diameter ratio on the stress field in the fiber and in the interface is analysed for an E-glass fiber and a high-modulus carbon fiber embedded in a polycarbonate matrix by varying the length to diameter ratios between 2.5 and 15.

DOI:10.1163/156855493X00040

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Rubber composites filled with carbon black and mica flakes were investigated by solid-state NMR and dynamic mechanical measurements. The results show that in rubber (butyl, EPDM, and chloroprene) and rubber composites filled with mica flakes there exists an interphase of considerable fraction with a different T1ρ value from the matrix. The hindered segmental motion in this interphase appears in the dynamic mechanical measurement with a high and broad tan δ and a high loss modulus E". The value of E" increases with increasing percentage of mica.

DOI:10.1163/156855493X00059

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A model is proposed to correlate the interfacial shear strength at the fibre-matrix interface, measured by means of a fragmentation test on single fibre composites, to the reversible work of adhesion between both solids, this quantity being defined as the sum of the dispersive and the acid-base interactions (physical interactions) between the fibre and the matrix. Whatever the nature of the fibres and the matrices, a linear relationship, passing through the origin, is established between the interfacial shear strength and the reversible work of adhesion. However, the slope of this straight line depends on the elastic properties and, more precisely, on the elastic moduli of both the fibre and the matrix. This leads us to express the reversible work of adhesion as the product of a mean intermolecular distance at the interface and an adhesive pressure related to the interfacial shear strength. The limits of the theoretical and experimental approaches leading to the establishment of such a model, as well as its domain of validity, are discussed.

DOI:10.1163/156855493X00068

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor