Low Temperature Curing prepregs are made exactly as conventional prepregs but have resin chemistries that allow cure to be achieved at temperatures from 60-100°C. At 60°C, the working life of the material may be limited to as little as a week, but above this working times can be as long as several months. The flow profiles of the resin systems allow for the use of vacuum bag pressures alone, avoiding the need for autoclaves.
Resins: Generally only epoxy.
Fibres: Any. As for conventional prepregs.
Cores: Any, although standard PVC foam needs special care.
i) All of the advantages ((i)-(vi)) associated with the use of conventional prepregs are incorporated in low-temperature curing prepregs.
ii) Cheaper tooling materials, such as wood, can be used due to the lower cure temperatures involved.
iii) Large structures can be readily made since only vacuum bag pressure is required, and heating to these lower temperatures can be achieved with simple hot-air circulated ovens, often built in-situ over the component.
iv) Conventional PVC foam core materials can be used, providing certain procedures are followed.
v) Lower energy cost.
i) Materials cost is still higher than for non-preimpregnated fabrics.
ii) An oven and vacuum bagging system is required to cure the component.
iii) Tooling needs to be able to withstand above-ambient temperatures involved (typically 60-100°C).
iv) Still an energy cost associated with above-ambient cure temperature.
High-performance wind-turbine blades, large racing and cruising yachts, rescue craft, train components.
Published courtesy of David Cripps, Gurit