Flexible and twistable composite material unit for connection of helicopter rotor blades to hub

摘要

The production of a long flexible, twistable, long composite part (17) comprising rods (1) of longitudinal fibres embedded in a resin and enclosed in a vulcanised elastomer (20) consists of separately making an assembly of elementary layers (5), each layer being obtained by laying side-by-side rods (1) of impregnated fibres and keeping them in a non-rigid state in a fabrication mould (6). The fibre rods (1) have their ends (3) placed between cut-out pieces of resin impregnated fibre layers. The layers are made rigid under pressure and heat followed by a cooling process. Several of the elementary layers (5) are assembled together to form a bundle (18) of rods regularly spaced. An elastomer (20) in a viscous state is injected into the bundle. The elastomer (20) is vulcanised to form a composite unit that is flexible and twistable. The resin used is a thermoplastic. The ends of the rods have a rectangular section and the central part joins the ends through a very short transition section having a constant cross sectional surface area. The cut-out pieces have fibres oriented at more or less 45 deg to the rod fibres.