A Study of the Use of Laminated Composite Wing Structures for Controlling the Divergence Speed of Forward Swept Wings

摘要

This thesis is an investigation of the effects of composite laminate orientation on the divergence problem of forward swept wings. The aerodynamic and structural properties are modeled with a doublet lattice technique and finite element method, respectively. The static equilibrium equation is applied to combine the two models. This results in an eigenvalue problem with the divergence dynamic pressure as the lowest eigenvalue. A computer program is written to formulate and solve the eigenvalue problem. It is applied to two cases of example wings. For the first case, 100% of the fibers are varied from 0 deg to 50 deg ahead of the structural swept axis for five different sweep angles. For the second case, only 70% of the fibers are varied while the remaining fibers are oriented at 90 deg and + or - 45 deg to the structural sweep axis. The results indicate that the divergence problem can be effectively controlled and possibly eliminated by properly orienting the composite laminates. The divergence speed was found to increase and reach a maximum as the principal fiber direction is swept forward. Maximum values occur for fibers oriented between 15 deg and 20 deg ahead of the structural swept axis for wing swept forward more than 25 deg. (Author)