Effects of Geometric Nonlinearity on Flexible Wing Structures

Abstract

An experimental remotely piloted aircraft named X-HALE was designed and built at the University of Michigan to collect experimental data for the flight dynamics of vehicles with very flexible wings. Similar aircraft with a wing span of 4 and 6 m were later developed and built at the Aeronautics Institute of Technology, Brazil, to study the flight dynamics and control of highly flexible aircraft. In the present Paper, the steady structural response of the wing of the X-HALE is investigated by the finite element method assuming 1) linear behavior (small displacement, small strain analysis) and 2) nonlinear behavior (large displacement, small strain analysis). This Paper aims to investigate the influence of geometric nonlinearities in the numerical prediction of load distribution and displacements along the wing span when compared with linear analyses results. For this purpose, four versions of the X-HALE with different structural layouts are presented. Two aircraft have a 4 m wing span constructed with fiberglass and aluminum, respectively. The other two have a wing span of 6 m and were also constructed with fiberglass and aluminum. Internal force redistributions were observed in the nonlinear structural analyses. The redistribution of these forces caused the twist angle to increase and the bending angle to decrease compared to the linear analyses when under the same loading conditions.