Interface molecular engineering of carbon-fiber composites

• Published in: Composites. Part A, Applied science and manufacturing Vol. 30; no. 1; pp. 49 - 57
• Main Authors: Lopattananon, N., Kettle, A.P., Tripathi, D., Beck, A.J., Duval, E., France, R.M., Short, R.D., Jones, F.R.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1999
• Subjects: A. Carbon fibre; B. Adhesion; B. Interface/interphase; Fragmentation test; Fragmentation test; A. Carbon fibre; B. Interface/interphase; B. Adhesion
• ISSN: 1359-835X; 1878-5840
• DOI: 10.1016/S1359-835X(98)00109-2

Adhesion of carbon fibers to epoxy and related resins is a complex subject requiring a fundamental understanding of: (a) the nature of the adhesive characteristics of the fiber; (b) the mechanisms involved; and (c) an appropriate quantification of adhesion. This paper discusses the application of plasma co-polymerization of acrylic acid/hexane, allyl alcohol/hexane and allylamine/octadiene, for the controlled functionalization of untreated type A carbon fiber through the deposition of thin, conformal coatings. The single-fiber fragmentation test has been used to estimate the influence of these pretreatments. The conventional data reduction technique and cumulative stress transfer function (CSTF) have been used as a measure of adhesion. The surface free energy of the coatings of allyl alcohol/octadiene deposited on glass plates, has also been estimated from the contact angle of polar and non-polar liquids. Hydrocarbon coatings resulted in a lower degree of adhesion than the parent untreated fiber. Increasing the concentrations of acrylic acid and allylamine promoted adhesion. This was attributed to the formation of covalent bonds between functional groups on the fibers and epoxy groups. The incorporation of allyl alcohol was less effective, because only dipole–dipole interactions were available. Contact angle measurements indicated that the polar component of surface free energy increased with the hydroxyl group concentration, despite no quantifiable increase in adhesion. The CSTF methodology has been shown to provide a precise estimate of adhesion.