Analytical and Finite Element Approach for the In-plane Study of Frames of Non-conventional Civil Aircraft

Abstract

In this paper, we study families of optimal frames of aircraft, as the fuselage cross-section vary, in the preliminary design. A complete closed-form solution of displacements and stresses for a circular arc, already introduced in a previous paper of the authors, is applied to study, in a wide generality, a fuselage cross-section made of tangent circular arcs, connected together in a $${\mathscr {C}}^1$$ -class curve. The closed-form solution is used here for two optimization case studies involving such piece-wise tangent cross-sections. First, we obtain minimum weight configurations of frames under pressurization, and also the effect of a small eccentricity with respect to the perfect circular fuselage is investigated; then, the constraints due to the presence of two floor decks are introduced. Second, the analytic solutions are validated by means of a finite element simulation in Abaqus and, to show the generality of the closed-form solution, the case studies are dedicated to non-conventional aircraft. Finally, we investigate the effects of the ellipticity ratio and the presence of a vertical and horizontal truss by means of finite element beam models.