Crashworthy Design of Aircraft Subfloor Structural Components

Abstract : Subfloor beams and bulkheads in aircraft structures are designed to carry longitudinal and shear loads resulting from fuselage bending and torsion. In crashes however, the subfloor is highly loaded in compression and shear. Especially the intersections of beams and bulkheads (cruciforms) represent stiff vertical 'hard points', and the resulting high peak failure loads under compression can create life threatening crash pulses to the occupants. For a commuter type aircraft subfloor aluminum as well as composite cruciforms were designed to match the same longitudinal stiffness of the floor beams and the same shear stiffness of the bulkheads. Various designs of the intersections including notched corners, corrugated and tapered edge joints, and less stiff laminate layups were investigated to reduce the initial peak loads, and to trigger efficient energy absorbing crush failure modes. (JES)