Advanced Continuous Tow Shearing for next generation AFP technology Dr Byung Chul (Eric) Kim [email protected] Complex geometry and Fibre steering In-situ impregnation Fibre steering technology is essential to manufacture complex composite parts. Even when the geometry is simple and developable, fibre paths sometimes need to be steered to avoid gaps and overlaps or to achieve designed fibre angle distribution with non-geodesic paths. As the complexity increases (e.g. doubly-curved surfaces), the geodesic paths deviate more from the designed fibre paths so that tighter steering radii are required. The built-in online impregnation device can produce a partially impregnated tow just before it is laid down. The produced tow has dry fibres on the top surface to allow the compaction shoe to slide on it and a sticky surface on the bottom for secure placement. Vertically distributed void areas provide sufficient fibre binding force along the thickness direction as well as in-plane shear flexibility. < Void distribution in a commercial prepreg (left) and the tow produced by in-situ impregnation (right) > Current technology and its limitation All existing fibre steering technologies (e.g. AFP, TFP) consider a tow as a narrow tape and apply in-plane bending deformation to lay up a curved path. This way of handling tow materials always produce defects such as fibre buckling, overlaps and resin pockets. Generally the minimum steering radius is limited to 0.5-0.6 m to minimise the defects. However, overlaps and gaps cannot be avoided. Fibre buckling Tow gaps ACTS (Advanced CTS) for 3D complex geometries For applying the steering capability of CTS to 3D complex geometries, 2 advanced functions should be added. Since the flat compaction shoe cannot conform with a convex or concave surface, a conformable compaction device with non-stick property is required. More importantly, since the surface cannot be tessellated by strips with a fixed width, the head needs to be able to adjust the tow width. Tow overlaps Tow overlap Game-changing fibre steering technology : Continuous Tow Shearing Impregnation device AFP Controllability of tow width AFP Tow drop Resin tape Target capability of ACTS Conformable compaction shoe for contoured surface CTS CTS steers the fibre path by applying in-plane shear deformation to a semi-impregnated tow which is supplied continuously. By changing the fundamentals of fibre placement, it can minimise fibre buckling and reduce the minimum steering radius by an order of magnitude over the AFPs. Compaction device with high surface conformity Tape take-up roller Tow feeding roller Compaction shoe Compaction shoe with an inflatable flexible tubing on its surface. - Provide a rigid edge boundary for shearing the tow material - Conformable with the uneven surface generated by tow thickness change (Tow thickness: 0.13 ~ 0.5 mm (0° ~ 75° of shear angle)) - Have non-stick property on the tow surface Gripping shoe dx < 1 mm CTS CT scan result Steering R: 40~100mm < Convex surface > Surface R of curvature: 80 mm < Concave surface > Surface R of curvature: 80 mm Impacts and Potential applications • • • • • Smooth surface without tow overlaps and gaps Steering R: 50mm Steering R: 150~700mm) Photoed by Dr. Nagelsmit and Dr. Gerrits of the NLR Steering R: 150mm High-quality composite products with complex geometries Automated layup head with low cost and simple mechanism Flexibility in selection of fibre and resin types More flexibility in design - exceptionally small steering radius Simplification of structural analysis without consideration of processinduced defects • Potential applications: Composite fan and turbine blades, Add-on module for AFP heads, In-house prepreg production
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