Metal/Composite Hybrid Rotor Blade Spar Construction

Unidirectional fiberglass straps are investigated as a means of providing metal rotor blades with a redundant load path and reduced fatigue crack growth rate. A comparison of crack growth rates for a metal/composite hybrid spar and a conventional metal blade structure are shown. Comparisons of ballistic impact damage for the hybrid spar and the metal spar are presented. Additionally, the results of small-specimen fatigue tests to investigate void propagation at the glass/metal interface are discussed.