Thermostructural design tools for hypersonic vehicles

The operating conditions of scramjet engines demand designs that include active cooling by the fuel and the use of lightweight materials capable of withstanding extreme heat fluxes and structural loads. As hypersonic flight is an emerging technology, there is limited ability to evaluate candidate material systems in hypersonic environments. This dissertation addresses the problem by developing an optimization protocol that establishes the capabilities and deficiencies of existing combustor panel designs and directs the development of advanced materials that will outperform existing high temperature alloys and compete with ceramic matrix composites (CMCs).;By incorporating models that characterize the key loading and boundary conditions of hypersonic combustors, the optimization protocol is able to rapidly survey the design space and facilitate communication between design variables and material properties. The code determines temperatures and stresses present in panels that line the combustion chamber and optimizes for minimum weight subject to two primary constraints: the stresses induced by thermomechanical loads remain below representative levels of material strength or elasto-plastic design rules; and the maximum temperature in the structure does not exceed the material limit. The results indicate that there are multiple avenues for achieving greater robustness and weight efficiency, including: (i) tailoring properties such as intermediate strength and material softening temperature and (ii) allowing localized plasticity. Design implementation is explored using laser heat flux experiments on convectively-cooled structures. The experiments serve as feedback for the optimization code and highlight benefits and concerns associated with allowing elasto-plastic response.