Prepreg Technology

Prepregs are semi-finished products consisting of endless fibres pre-impregnated with a thermoset matrix polymer, which is in uncured or partly cross-linked state (B-stage). Unidirectional fibres as well as woven fabrics can be used as reinforcements.

By the usage of prepregs, a separate infiltration step of the fibres with the matrix polymer is not anymore a need. Thus, it is possible to achieve a high fibre volume content and complex part geometries can be realized. The processing of the prepregs can be done manually by cutting and placing, however for industrial applications fully automatized placement processes are necessary. The reproducibility of these production methods qualifies the prepreg technology for the serial production for high-performance lightweight structures such as structural materials in aerospace industry.

Prepreg materials are of particular interest for the investigation of mechanical properties of fibre reinforced plastics as nearly perfect laminates without any inhomogeneities such as stitching yarns can be produced. Due to that, it is possible to systematically and precisely study and explain the relationships in between the neat resin and the laminate properties.

The technical scale prepreg machine at the University Bayreuth is a special equipment for the development of novel prepreg resin systems. The pilot prepreg plant offers the ability to produce aerospace quality prepregs with low amount of resin by using hot-melt processing. The reinforcing fibres (up to 32 rovings) can be directly pulled over a in-line spreading. Besides fabrics can be unwinded and subsequently impregnated with the resin. A special feature of the machine is the innovative and highly flexible coating unit, which combines a comma bar system, a roll coater and a foulard impregnation unit. Therefore, various thermoset matrix systems in the viscosity range of about 10 to 50000 mPas can be processed. In addition, the processability of matrices can be studied and compared by using above mentioned different impregnation technologies. The B-Staging zone consists of two calendars and can be heated up to 250 °C which renders it possible to process high temperature thermosets such as benzoxazine or cyanate ester resins.

Additionally, qualified laboratory facilities of the department Polymer Engineering at the University Bayreuth offer thermal, rheological and mechanical tests of the prepreg resin systems, as well as the production of laminates from prepregs by compression moulding and the following thermal and mechanical (quasi-static and dynamic) testing methods.


Contact: M. Sc. Martin Demleitner
Phone: +49(0)921 55 74 76
Telefax: +49(0)921 55 74 73
Email: martin.demleitner@uni-bayreuth.de

 

Download: Prepregs at Polymer Engineering