Gust Load Alleviation of Flexible Composite Wing

Abstract

Gust load due to atmospheric turbulence is mandatory to be considered in aircraft

analysis as part of airworthiness requirement. This safety related issue becomes more

relevant recently in relation to the global warming that induces more frequent and

extreme atmospheric disturbances encountered during air transportation. A direct

application of gust load on the wing structural analysis, however, is not

recommended since it will result in a significant weight increase due to the

overdesign of the wing structure. At this point, the gust load alleviation plays an

important role to effectively utilize the wing structural flexibility without ignoring the

safety issue. In the present work, a method to alleviate the wing gust load is

proposed by considering different configurations of the wing planform, wing sweep

angle, wing dihedral angle and composite material layers. The objective of the study

is to minimize the wing root bending moment due to the gust. The gust load analysis

of the Kim-Hwang’s wing model will be used and the results are compared to the

literature for the validation purpose. A finite element approach is used to simulate

the wing structure in combination with the doublet lattice method to model the wing

aerodynamics. It is found that the wing dihedral angle plays insignificant changes to

the wing root bending moment due to the gust load. The wing sweep angle,

however, gives significant changes to the wing root bending moment. For the

present configuration, the optimum swept back configuration with a 45° sweep angle

and optimum composite lay-up showed an average decrease of the bending moment

by 12% for frequency range of 0 to 100 Hz.