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    Low-Weight, Impact-Resistant Helicopter Drive Shafts

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    The advantages and disadvantages of all composite helicopter drive shafts are discussed. Previous research has shown that all graphite/epoxy torque tubes severely delaminate under low-velocity, low-energy impact tests simulating accidental “tool drop” conditions.

    In response to the need for weight savings without the sensitivity to low-energy impact, two composite metal hybird drive shafts have been designed and tested. These are constructed with unidirectional (parallel to the tube axis) boron epoxy composite, for increasing the flexural stiffness, sheathed with an inner and outer metal tube, for torsional strength and damage resistance.

    A limited number of ballistic and low-energy impact tests were conducted. Damage from a 12 ft-lb simulated “tool drop” test was minimal. The same tube while sustaining 1/3 of its undamaged design torque was perforated by a fully tumbled 30-caliber projectile and subsequently failed at 2/3 of its undamaged ultimate load.

    The hybird drive shaft is considered to have a significant weight savings potential. As compared to an all-aluminum drive shaft, its specific flexural stiffness is increased by a factor of 2.6 and its specific critical buckling stress by a factor of 1.5. As compared to an all-boron epoxy drive shaft, its specific flexural stiffness is approximately equal and the critical buckling stress is reduced by 40 percent. In addition to the advantage of impact resistance, the hybrid designs offers the advantage of metal-to-metal attachment with conventional splicers and nuts and bolts.


    composite materials, helicopters, driveshafts, boron, hybrid driveshafts, impact strength

    Author Information:

    Figge, IE
    U. S. Army Air Mobility Laboratory, Fort Eustis, Va.

    Henshaw, J
    Advanced Composites Section, Lowell, Mass.

    Roy, PA
    Advanced Composites Section, Lowell, Mass.

    Olster, EF
    Advanced Composites Section, Lowell, Mass.

    Committee/Subcommittee: D30.05

    DOI: 10.1520/STP35514S