A microbond method for determination of the shear strength of a fiber/resin interface

The carbon fibre/epoxy interface: a review

The interfacial properties between carbon fibers and surrounding matrix of a composite are drastically affected by interfacial structure. This structure mainly relates to the surface physico-chemistry of the fiber, which includes its surface chemical groups and microstructure, morphology, surface area, and surface free energy. These properties can be changed by various surface treatments, including various dry and wet oxidation steps, plasma treatment, electrodischarge, and fiber sizing or coating. These methods improve the interfacial properties significantly and synergistically, although each treatment has its specific application area.

A review of methods for improving the interfacial adhesion between carbon fiber and polymer matrix

Chemical modification of carbon fiber surfaces by nitric acid oxidation followed by reaction with tetraethylenepentamine

Microbond method for determination of the shear strength of a fiber/resin interface: Evaluation of experimental parameters

The electrodic polymerization on graphite fibers of a variety of monomers having different types of functional groups has been investigated. In addition to vinyl polymerization, some novel polymerizations of cyclic functional groups have been conducted under appropriate polymerization conditions. In many instances, the grafting of the surface polymer to the fiber has been confirmed. The stereochemical configuration of poly(methyl methacrylate) resulting from electropolymerization was measured, but conclusive evidence could not be obtained for the occurrence of stereo-regulation in electrochemical polymerization on graphite fiber surface; Composite specimens were prepared by the incorporation of the coated fibers in an epoxy matrix. It was demonstrated that the effect of electropolymerization on the interfacial properties of the resulting composite was manifested in variations of the measured interlaminar shear and impact strengths of the composite specimens. The increase or decrease in interlaminar shear was accompanied by the usually observed reverse change in impact strength. In exception to this general trend, it was also indicated that the shear and impact strengths could simultaneously be increased. Implicit in these findings is the contribution of the electrochemically formed interlayer to one or more of the toughening mechanisms that are available to fiber reinforced composites. The potential value of interphase modification by electrochemical polymerization is thus clearly indicated.

Electropolymerization on graphite fibers

Polymer coatings were produced on graphite fiber electrodes by electroinitiated polymerization in an electrolytic cell containing monomer. The adhesion of the coated graphite fibers to an epoxy matrix has been measured by single fiber pull-out tests. The measured values of the pull-out force, and scanning electron micrographs of pulled-out fibers reveal three modes of failure and degrees of adhesion independent of the type of polymer coating. It is seen that the initial formation of a resin cone on the embedded fiber contributes significantly to the measured values of the pull-out force for fine, 5–10 μm carbon fibers but not for larger diameter (>50μm) fibers. The effect of the surface treatment on the interfacial properties of composites prepared from the coated fibers was manifested in variations of the interlaminar shear and impact strengths of epoxy composite specimens which were sensitive to the type of coating polymer. Polymer coating of carbon fibers by electrodic processes is thus seen a...

Interfacial Aspects of Polymer Coating by Electropolymerization

Carbon fibers are electrocoated by electrodeposition or electropolymerization to facilitate the formation of char, a nonconductive residue or fiber clumps when the coated fibers within a composite are subsequently exposed to fire. Coating materials or precursors are phosphorus compounds, titanates, polyimides, polyquinoxalines, nitriles, or boric acid.

Treatment of carbon fibers to decrease electrical hazards of conductive fiber fragment release

Surface modification of wood flakes by oxidation with nitric acid has been investigated at three different moisture contents of wood, and two different concentrations of the oxidant. It is shown that a significant number of the acid groups generated are chemically linked to wood. Increasing moisture content in wood has the effect of local dilution of the nitric acid oxidant while reduction in moisture content of wood during drying makes potential oxidation sites less accessible. Thus, two different regimes of oxidation, one of more accessible, and another, of less accessible, sites are observed. The nature of the generated acid is established as carboxylic, which is capable of undergoing a coupling reaction with 2-(l-aziridinyl)ethyl methacrylate. The catalysis of in situ polymerization of furfuryl alcohol by bound acid has also been shown to occur.

R. V. Subramanian

Papers

Electropolymerization on graphite fibers

Interfacial Aspects of Polymer Coating by Electropolymerization

Treatment of carbon fibers to decrease electrical hazards of conductive fiber fragment release

Surface Modification of Wood Using Nitric Acid

Electroinitiated polymerization of aziridines