Structural Design of Wing Twist for Pitch Control of Joined Wing SensorCraft

Abstract

This research investigated two aspects of the aft wing structure of a joined wing SensorCraft. First, the efficacy of a novel approach for incorporating wing twist for pitch control was analyzed. This design involved adding a spanwise sliding joint into the wing structure at the lower aft spar of the vehicle's aft wing. Second, the joint section where the forward and aft wings connect and form the outboard wing was redesigned and analyzed to improve the load transmission between the wing spars. Using MSC.NASTRAN, linear and non-linear static analyses were performed to examine the efficiency of the wing twist sliding joint and the forces required to achieve sufficient angular deflections for control. MSC.Patran was then used to perform post-processing of the raw data. Several variations of sliding joint location and composite ply angles were conducted. The sliding joint produced marked improvement in angular deflection over the baseline configuration. Surprisingly, however, ply angle did not have a large effect on the resulting deflections. Additional sliding joints incorporated into the wing structure produced no notable improvements in the obtained deflections either. Although the strain induced into the structure by the aft wing twist was on the order of the aerodynamic forces alone, the force required to twist the wing was significantly reduced by adding the slit in all cases. Flutter speed did not differ notably by the addition of the slit into the aft wing, yet some reduction in buckling strength was noted. The redesigned joint planform does appear to recover some of the buckling resistance lost due to the slit.

Review of Structural Issues in the Design of a Box Wing Aircraft

“…Rasmussen, et al [18] proposed a design methodology for Joined-Wing configurations that integrates a geometric model with other disciplinary models using the Adaptive Modelling Language. This creates a user interface that allows for the structural and aerodynamic analysis of the Joined-Wing configuration.…”

“…This creates a user interface that allows for the structural and aerodynamic analysis of the Joined-Wing configuration. Based on results from the design methodology, Rasmussen, et al [18] conclude that non-linear structural analysis is important to accurately capture the large deformations that occur on a Joined-Wing configuration.…”

“…Kimler and Canfield [18] studied the structural design of wing twist for pitch control of a Joined-Wing sensorcraft. The investigation involved adding a span-wise sliding joint into the wing structure of the vehicle's aft wing.…”

Challenges, Ideas, and Innovations of Joined-Wing Configurations: A Concept from the Past, an Opportunity for the Future

“…The necessity of increasing the area available to sensors and avoid sensor interference demands a minimization or possibly elimination of control surfaces. With this in mind, references [31,35,36,188] suggested to control pitch by twisting the aft wing. This twist was induced by an actuator located in the vertical stabilizer applying a force to the root of the aft-wing.…”

Buckling Alleviation for Joined-Wing Aircraft

“…The nonlinear analysis shows that the BAC delays the onset of nonlinear behaviour and that the critical buckling loads of the conventional configuration are drastically overestimated by the linear analysis, which means that BAC performs much more effectively than the initial linear analysis suggests. [1] and has been considered in recent years for the design of Unmanned Aerial Vehicles (UAVs) such as Boeing's SensorCraft [2,3,4]. In light of much research regarding the achievability of its proposed benefits, this unconventional configuration has not been accepted as a viable design option for transport aircraft.…”