Response of segmented-stiffness composite cylinders to axial end shortening

Abstract

Composite fuselage structures that utilize different laminates in the crown, sides and keel may be part of future aircraft designs. Here exact, approximate and finite element solutions for the geometrically linear response to axial end shortening of cylinders constructed in this segmented fashion are investigated. It is concluded that circumferential displacements are the feature that distinguishes these designs from more conventional single-laminate designs. Additionally, it is the difference in effective laminate Poisson's ratios from one segment to the next, as opposed to the difference in effective laminate extensional or shear moduli, that is responsible for the circumferential displacement. However, for short cylinders ( L R = 2) with clamped boundaries, the circumferential displacement is greatly suppressed relative to the case of longer cylinders ( L R = 20) , while the radial displacement is not as dramatically influenced by length. This trait can be traced to the wavelengths that govern circumferential and radial responses, and can be interpreted as the Saint-Venant effect for circumferential displacement having a different characteristic length than the Saint-Venant effect for radial displacement.