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An experimental method for determining the interfacial fracture energy of a single fibre undergoing peeling is presented. Peeling of a partially embedded single fibre is observed under scanning electron microscopy. The fracture energy of the fibre/matrix interface is determined by analysis of the measured curvature of the fibre near the crack tip. This study serves as a demonstration of concept for the characterization of fibre/matrix interfaces through the single fibre peel experiment. A glass fibre/vinylester interface is used as an initial test case, from which obtained interfacial fracture energies was found to be in the range from 2 Jm−2 to 14 Jm−2.

Fibre-reinforced polymer composites are gaining increasing attention in various applications for constructing mechanical structures such as wind turbine blades. The interface between fibres and a polymer matrix should be optimally designed to promote the mechanical performance of the composites. Plasma treatment shows obvious advantages over conventional approaches, since it has the characteristic of environmental friendliness, low-cost, and easy operation. A plasma can be favourably generated at atmospheric pressure. One of the most commonly used atmospheric pressure plasmas is a dielectric barrier discharge (DBD). In the present work, an air-to-air DBD is introduced. The DBD was generated in a gas mixture of helium and fluorocarbon between a rod-shaped water-cooled powered electrode covered with alumina and a one-dimensionally movable ground aluminium plate. Polyethylene terephthalate films were used as model specimens, and attached on the aluminium plate for the surface modification. The results indicate that specimen surfaces can be oxidized or fluorinated, depending on the conditions, and that the gap between the electrodes and gas flowrates significantly affect the treatment effect.

Sized glass fibre bundles were treated using atmospheric pressure plasma in a helium/tetrafluoromethane gas mixture. X-ray photoelectron spectroscopy showed that fluorine was introduced onto the sizing surface. A new analysis method (dynamic micro-wetting) to determine the wetting rate of the plasma-treated fibre bundles is presented. The dynamic micro-wetting test using glycerol as a test liquid showed a reduced wetting rate after plasma treatment. It is demonstrated that dynamic micro-wetting is a useful tool for the characterization of fibre bundle wetting.