Integral Design and Optimisation Process for a Highly Flexible Generic Long Range Jet Transport with Flight Mechanic Derivative Constraints

Abstract

Due to the increased application of carbon fibre reinforced plastics (CFRP) in the aircraft industry within the past decades, design of primary load carrying structures has vastly evolved. Ultimately, this led to weight saving and a wider design space as the result of reduced material density and the anisotropic nature of the composite. However, the aforementioned design space is currently limited by uncertainties such as material imperfections, open hole tensions or plate boarder stresses. These uncertainties are commonly overcome by applying large safety margins, limiting the benefit of replacing aluminium with carbon fibre. To investigate this matter, a highly flexible long range jet transport, resembling an Airbus A350- 900 or a Boeing 787-10 class aircraft, is taken as a reference. Its simulation model components are set up using an in-house model generator. In doing so, the main load carrying structure of the wing is optimised by the means of an comprehensive loads and optimisation tool chain built around MSC.Nastran. By applying an aeroelastic tailoring approach the flight mechanic stability of the aircraft is guaranteed, while the calculation of the sensitivities in the gradient based optimisation incorporates the change in the dimensioning loads. To obtain a highly flexible structure, a carbon fibre laminate optimisation is set up, using lamination parameters in combination with large strain allowables (up to 8000 µ in tension). The result is a highly flexible wing structure, featuring a vertical displacement of up to 10 % with respect to the semi-wingspan during cruise flight. Besides the impact of varying boundary conditions and optimisation strategies on the flexibility and the primary structural mass of the wing, the development of significant constraints and modal properties is investigated.