Nonlinear Analysis of PrandtlPlane Joined Wings: Effects of Anisotropy

Abstract

Structural geometrical nonlinearities strongly affect the response of Joined Wings: it has been shown that buckling evaluations using linear methods are unreliable and only a fully nonlinear stability analysis can safely identify the unstable state. This work focuses on the understanding of the main physical mechanisms driving the wing system's response and the snap-buckling instability. Several counterintuitive effects typical of unconventional non-planar wing systems are discussed and explained. In particular, an appropriate design of the joint-to-wing connection may reduce the amount of bending moment transferred, and this is shown to eventually improve the stability properties although at price of a reduced stiffness. It is also demonstrated that the lower-to-upper-wing stiffness ratio and the torsional-bending coupling, due to both the geometrical layout and anisotropy of the composite laminates, present a major impact on the nonlinear response. The findings of this work could provide useful indications to develop effective aeroelastic reduced order models tailored for airplane configurations experiencing important geometric nonlinearities such as PrandtlPlane, Truss-braced and Strut-Braced wings, and Sensorcrafts.

Post-critical analysis of highly deformable Joined Wings: The concept of snap-divergence as a characterization of the instability

“…3) is a PrandtlPlane-like configuration (see Demasi et al, 2013b;Cavallaro et al, 2012Cavallaro et al, , 2014a) featuring a swept-back lower wing and a swept-forward upper wing. It is named PrP40.…”

Electric Propulsion Concepts for an Inverted Joined Wing Airplane Demonstrator

“…Lastly, we propose that the application of an inverted joined wing configuration could also help in solving the problem of global buckling of the joined wing airplanes reported by several researchers [18][19][20]. The direction of critical load (lift + drag in point A of the load envelope) points upwards and forwards.…”

Aerodynamic Shape Optimization of a Box-Wing Regional Aircraft Based on the Reynolds-Averaged Navier-Stokes Equations

“…Snap-Buckling Recent studies [94,95] have suggested that the unique nonlinear structural response of the box-wing aircraft configuration requires a specialized treatment for buckling. Indeed, these studies demonstrate the unreliability of linear buckling theory, which often leads to an overstimation of the critical load point.…”