21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-1.2.2

DESIGN AND VERIFICATION PHILOSOPHIES FOR HIGH PERFORMANCE AEROSPACE VEHICLE STRUCTURES UNDER COMBINED MECHANICAL AND THERMAL LOADING

Berkes U. L.
European Space Agency, The Netherlands

Keywords: design, high performance aerospace vehicle structures, mechanical and thermal loading

The design of high performance aircraft structures is driven mainly by the sustained aerodynamic heating during high-speed flight. An extended dimensioning and verification philosophy is required for the air-frame structure design of these aircraft, which adequately considers the combination of the mechanical loads and of the thermal loads. The very sensitive design of these vehicle shows that if a marginal design philosophy has been chosen, the design may become unfeasible, because of too a high structure mass, or because a sound verification becomes virtually impossible to achieve. Two basic philosophies exist for combination of the thermal environment to the mechanical environment: (1)By applying the Safety-Factor on the induced thermal loads and (2) By applying the Safety-Factor on the heat fluxes or performance parameters. Computations have been carried out for both design philosophies, based on flight conditions for re-entry vehicle. Three types of structures have been considered for comparison of the efficiency: Aluminium fuselage structure covered by a thermal insulation system, Titanium interface structures and 3-D Carbon/Carbon load carrying hot-structures. The most favourable design philosophy is outlined for each structure. Buckling phenomena due to combined thermal and mechanical loading are discussed. The design philosophies are further discussed with respect to verification testing.

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