Investigation into the static and fatigue behaviour of a helicopter main rotor yoke made of composite materials.

摘要

The Bell Helicopter M407 main rotor yoke is a structural helicopter part made of laminated glass-epoxy composite material. Delamination failure of the main rotor yoke under static and fatigue loading conditions is investigated, both analytically and experimentally. A finite element model of the yoke is developed with a commercial finite element code, using the 'dummy plies' technique to allow modeling of a tapered laminate. The model is validated against the available experimental data. A set of static and fatigue experiments---limited to beamwise bending loads---are performed on representative test specimens cut out of actual yokes. The model is able to accurately predict the location of initial static failure, which corresponds to the interlaminar shear stress concentration predicted by the stress analysis. Results of the specimen fatigue tests are successfully correlated with the glass-epoxy material fatigue properties, using the Normalized Fatigue Life Model and the finite element model of the specimen.