In a pilot project, FIBRE worked with AIRBUS Operations GmbH, KARL MAYER MALIMO Textilmaschinenfabrik GmbH, KraussMaffei Technologies GmbH, Ferdinand Stükerjürgen GmbH and TU Chemnitz to produce aircraft window frames successfully using a thermoform and injection moulding process. Shorter cycle times were possible, resulting in an increase in productivity.
Structural components for aircraft made from fibre polymer composites frequently comprise duroplastics shaped in prepreg and resin transfer molding (RTM) processes. Celanese adds that the greatest disadvantage of this process is the extensive drying times required for the matrix to cure, which requires extensive drying time for the matrix to cure.
"From a production point of view there is actually a great deal in favour of thermoplastic materials like Fortron PPS, which are often more economical," said Peter Radden, Fortron PPS specialist. "Fortron PPS is more dimensionally stable, chemical and temperature resistant, and has a long tradition in aircraft construction where it is often the material of choice in structural components."
FIBRE uses prepregs that contain additional inlaid thermoplastic fibres, as well as carbon fibres, to lend structure to the window frames. These prepregs are processed to form structural inlay preforms - versions made from multi-axial fibre inlays (MAG) are used to shorten cycle times. FIBRE also produced Tailored Fiber Placement Preforms (TFP) parallel for precise fibre alignment.
The matrix of knit and weft fibres is formed in the subsequent consolidation in a variotherm press. In this process, the Fortron PPS fibres in the prepreg ensure homogenous matrix distribution. After consolidation, the structure inlays are sprayed with short fibre-reinforced Fortron PPS to add integral stiffening or functional elements which would be much more difficult to implement with continuous fibre-reinforced materials. The combination of thermoforming and injection moulding makes the process more cost-effective and allows for higher production volumes in a shorter time.
