1433. High Strain Composite Wing Development for Subsonic Patrol V/STOL Aircraft

Paper

Abstract

The driving force behind composite material development in the Navy is the requirement for lighter
weight structures. Carrier based aircraft in general and vertical/short take-off and landing (VSTOL)
aircraft in particular have severe weight constraints. Minimizing airframe weight is crucial to the
success of the VSTOL aircraft, and the maximum effective utilization of advanced composite materials
is essential to the attainment of this goal. The use of advanced composite materials offers greatest
technological improvement over historical airframe weight and has demonstrated weight savings of 20
to 25 percent.
However, composite wing structures are currently limited to design ultimate strain levels substantially
below the failure capability of the basic composite material due to the effects of strain concentrations in
the design. Fastener holes, access door cutouts, rib tab extensions, pylon attach points, and swept wing
carry-thru structures are typical sources of strain concentrations in current composite wing design.
Reducing the effect of such concentrations for ultimate design conditions offers promise of increasing
composite wing structural efficiency.
Advanced composite design improvements that permit a substantial increase in composite wing design allowables
without sacrifice to fatigue life, damage tolerance, survivability, and repairability are discussed in
this paper. A 20 percent weight savings over current composite wing designs was used as a program objective.
Grumman’s design 698, a subsonic patrol multi-mission VSTOL aircraft, was used as a baseline for the study.