Flexible Matrix Composites Applied To Bearingless Rotor Systems

A new composite structure in which the typical epoxy matrix is replaced by an elastomer is introduced, namely, flexible matrix composites. Some of its properties, particularly its elastic constants, are discussed in terms of laminate angle, constituent properties and fiber fraction. Unidirectional flexible matrix composites are applied to the requirements of a bearingless rotor flexure. This is done by assessing load-deflection characteristics and strengths of test coupons in critical loading modes. Preliminary results indicate a short, light weight flexible matrix composite flexure is feasible. Flexible matrix composites are also applied to a pitch control tube of a typical 3,000 kg helicopter. A full-scale prototype was fabricated and tested both statically and dynamically. It endured 50 X 10^6 cycles of combined bending and torsion loads with only a modest loss of properties.