A spanwise twisting morphing flap device featuring multistability

A novel span-wise twist morphing flap device is presented in this paper which provides smooth trailing edge deflection variation along the wing span. The span-wise morphing trailing edge proposed consists of carbon fibre reinforced plastic laminate spars and ribs which are assembled in a grid pattern. The composite laminate spar strips are manufactured in a stress free state with an initial curvature and are prestressed by flattening before assembly, which provides a heightened strain energy state of the structure. The prestress effects in the spar strips lead to structural stiffness tailorability and multistability. Design parameters including laminate layups of the spar and rib and the initial curvature in the spar strips are investigated in a preliminary optimization study using an analytical model. Results show that by tailoring the structural design, the stable equilibria configuration of the span-wise morphing trailing edge can be set over a wide range of torsion angles and a zero torsional stiffness span-wise morphing trailing edge design can be achieved as well. Results are verified against finite element analysis and good correlation is found.