Large-volume production of continuous fibre-reinforced PU parts

The aim is to develop this fast, fully automated production process for fibre-reinforced structural parts to make it suitable for large-volume manufacturing processes. The project is being sponsored by the German Research Foundation (DFG) as part of the Research Unit 860 "New process chains for composites: Integration of preforming, impregnation, forming and curing".

Compact polyurethanes are used as the matrix material. Not only are they noted for their wide range of properties, they also offer many other advantages due to the fact that their reaction kinetics can be adjusted over a broad range.

For production of the composite parts, textile preforms are impregnated with oriented, non-compacted continuous fibres by means of the spray technology. A non-foaming Baypreg polyurethane from Bayer MaterialScience AG, Leverkusen, Germany, serves as the matrix material. A polyurethane spray centre was built at IKV's Composites pilot plant with the support of KraussMaffei Technologies GmbH, Munich.

Application of the matrix and pre-impregnation of the dry preforms are carried out on a vacuum-assisted impregnation tool in just 30 seconds. Complete consolidation and crosslinking of the impregnated textile are performed in a newly developed compression moulding tool. This tool is operated isothermally at 100 °C and enables excess resin to flow away in controlled side-cavities.

Through the combination of the spray process and the adapted compression technology, parts can be produced in sizes of 500 x 500 x 3 mm³ with a fibre volume content of over 50 percent in cycle times of less than five minutes. The originally targeted process time of ten minutes has thus been more than halved and is to be reduced even further through modification of the chemical composition of the polyurethane.

IKV would like to thank DFG for its support of this subproject 4 within Research Unit 860.