Influence of Joint Fixity on the Structural Static and Dynamic Response of a Joined-Wing Aircraft Part I: Static Response

A comparative study is made between the internal stress resultants in a joined-wing structure that arise from employing eight different wing-joint fixities for an assumed flight loading condition. The joint fixity refers to the type of attachment that connects the rear wing tips to the forward wing tip or inboard spanwise point. The study is carried out employing both experimental as well as computational investigations.

The study of the eight joint configurations indicates that the rigid joint is the most practical. This conclusion was based upon a comparison as to which wing joint provided the largest reduction in the main wing classical cantilever wing root bending moment. This moment reduction was subject to the constraint that no excessive joint reactions are introduced which tend to promote stiffness instabilities of the rear wing (which acts as a strut brace to the forward wing). Additional considerations also indicate the optimality of the rigid joint with respect to the total level of strain energy required to resist a given loading, as well as to the uniformity of the strain energy density imposed by the loading throughout the wing structure.