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Macromechanical Behavior of a Laminate
Published in Robert M. Jones, Mechanics of Composite Materials, 2018
Bend-twist coupling stiffnesses are the mechanism for control of forward-swept wings on the X-29A in Figure 1-37. Forward-swept wings are subjected to aerodynamic forces that tend to twist the wing about an axis that is along the wing and off perpendicular to the fuselage by the angle of the wing sweep, e.g., My in Figure 7-10. Aerodynamic divergence (gross wing flapping that in the limit tears the wing off) is the possible result. A composite laminate with laminae at various angles to the wing axis has D16 and D26 that cause the wing to twist in the opposite sense to the aerodynamic wing-twisting effect seen in Figure 4-17. Countering the wing-twisting effect on a metal wing causes large weight and cost penalties because the only way to create a structural D16 and D26 for metal wings requires many stiffeners at an angle to the wing axis. In contrast, the laminated composite wing might require a few extra layers of material, but no stiffeners, so both the weight and cost penalties are small to achieve the aircraft performance advantages of a forward-swept wing (e.g., improved agility and improved high angle-of-attack flying qualities). In fact, a forward-swept wing can be smaller in size, weight, and cost than the usual rearward-swept wing. Concepts of what has become known as aeroelastic tailoring of composite structures are reviewed by Hertz, Shirk, Ricketts, and Weisshaar [4-4].
Flow Visualization By Direct Injection
Published in Richard J. Goldstein, Fluid Mechanics Measurements, 2017
Thomas J. Mueller, F. N. M. Brown
Interest in forward-swept-wing aircraft is growing rapidly. This type of configuration, made possible by lightweight, nonmetallic composite materials, would have greater range and fuel economy, lower stall speeds, spin resistance, and improved low-speed control for easier landings and takeoffs than the present swept-back-wing design. Some of the present aircraft designs use canards to improve maneuverability. The forward-swept-wing design concept is relatively new, and therefore a large number of analytical and experimental studies are necessary to understand the complex flow over such a geometry.
Calculation of flutter and dynamic behavior of advanced composite swept wings with tapered cross section in unsteady incompressible flow
Published in Mechanics of Advanced Materials and Structures, 2019
Although the primary motivation for a positive sweep angle is to improve aircraft performance by increasing the critical flight speed, sweep angle has important effect on the aeroelastic behavior of the aircraft wing as well. There are two ways in which the sweep influences the aeroelastic behavior. One is the loss of aerodynamic effectiveness (Un = U∞cos Λ) and the second effect is the influence of bending and torsion slopes on the effective angle of attack and downwash velocity, which leads to an aeroelastic bending–torsion coupling. This coupling has an important influence on both divergence and load distribution and makes the forward swept wing more susceptible to divergence. Figure 24 displays the effects of different sweep angle on response. The response for the sweep angle Λ = −40°, 0°, 40° is considered. As the sweep angle increases, the response amplitude for bending mode also increases. Likewise, the time needed for response damping also increases.
Active aeroelastic wing application on a forward swept wing configuration
Published in Engineering Applications of Computational Fluid Mechanics, 2019
Rongrong Xue, Zhengyin Ye, Kun Ye
The forward swept wing (FSW), which is a challenging configuration, is subject to aeroelastic torsion divergence problems at high dynamic pressure (Rongrong, Zhengyin, & Gang, 2016; Weisshaar, 1979). The aeroelastic torsion divergence problem is caused by the aerodynamic center (AC) always positioning in front of the structure stiffness center, which results in a head-up twist on the FSW. This characteristic increases the local angle of attack (AOA), and generally generates more lift and aeroelastic torsional deformation until the structure fails because of the uncontrollable aerodynamic forces. This feature seriously restrains the application of FSWs on commercial airplanes.