This paper presents a study of the cure of carbon fiber composites by the direct application of an electric current. The conductivity of carbon fiber enables the individual fibers to act as heating elements.The result is a large number of heating elements throughout the composite structure. These heating elements locally heat the resin surrounding them, resulting in the resin curing. This study shows that cure of composites is achieved in samples up to 60 £ 25 cm.Initially, the required contact arrangement to obtain a uniformly heated panel is assessed and an optimum arrangement achieved. Following this, the change in required energy as the sample thickness and sample length are changed is measured. The degree of cure is compared to conventionally cured composites using differential scanning calorimetry (DSC). Three-point bend testing is used to determine the flexural strength and modulus of the composite samples. The results show that a comparable level of cure can be obtained using direct application of an electrical current as that obtained using autoclave cure and oven cure processes.

Highlights:-The powder-epoxy towpregging process was described in detail for both carbon fibres and basalt fibres.-Excellent static mechanical properties were reported for unidirectional carbon-fibre/powder-epoxy composites and the influence of fibre volume fraction (FVF) was analysed.-Two types of basalt fibre were tested, showing comparable mechanical properties to glass fibre composites.-A hygrothermal study of both carbon-fibre composites and basalt-fibre composites showed that the latter had a greater sensitivity to water uptake and immersed ageing.

The various methods of self-sensing and self-healing developed within the Composite Systems Innovation Centre, University of Sheffield, are reviewed. Damage sensing using electrical resistance in carbon fibre reinforced composite or using the fibres as optical sensing elements in glass fibre reinforced composite is demonstrated. Amelioration of low level damage is demonstrated in both monolithic composite materials and sandwich structures using direct chemical reactions within the matrix without the use of encapsulants. These reactions can be activated by resistive heating of the material itself. The use of a combination of these techniques could create a truly smart structure able to both sense and repair damage and degradation.

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