Dry fabrics are laid up interleaved with layers of semi-solid resin film supplied on a release paper. The lay-up is vacuum bagged to remove air through the dry fabrics, and then heated to allow the resin to first melt and flow into the air-free fabrics, and then after a certain time, to cure.
Resins: Generally epoxy only.
Cores: Most, although PVC foam needs special procedures due to the elevated temperatures involved in the process.
i) High fibre volumes can be accurately achieved with low void contents.
ii) Good health and safety and a clean lay-up, like prepreg.
iii) High resin mechanical properties due to solid state of initial polymer material and elevated temperature cure.
iv) Potentially lower cost than prepreg, with most of the advantages.
i) Not widely proven outside the aerospace industry.
ii) An oven and vacuum bagging system is required to cure the component as for prepreg, although the autoclave systems used by the aerospace industry are not always required.
iii) Tooling needs to be able to withstand the process temperatures of the resin film ( which if using similar resin to those in low-temperature curing prepregs, is typically 60-100°C).
iv) Core materials need to be able to withstand the process temperatures and pressures.
Aircraft radomes and submarine sonar domes.
Published courtesy of David Cripps, Gurit