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Abstract
There has been a global increase in the research and development of military hypersonic technology. Thermal directed-energy systems have been identified as a capability to defend against hypersonic threats.
A numerical and experimental methodology for studying the effects of thermal energy deposition on representative hypersonic panels is presented. This thesis contains four sections, (i) theory and implementation of a first-order, fast, transient thermal-structural code: "Rapid Engineering Determination of Heating over a Trajectory'' (REDHOT), (ii) thermal-structural results from two case studies using REDHOT with energy deposition, (iii) development of an experimental technique to create and measure adverse thermal-structural failure caused by energy deposition, (iv) experimental validation of the technique.
The first-order thermal structural code uses the reference-enthalpy method and two-dimensional conduction to calculate the thermal state of a representative hypersonic panel. Thermal stresses are calculated analytically with linear plate theory and non-linear finite element analysis simulation.
Numerical results using the HyperX and HEXAFLY-INT trajectory as case studies are presented. REDHOT calculated nominal temperatures without energy deposition are within 1-10% of reported results in literature, acceptable for the first-order analysis in this thesis. Energy deposition is observed to have a greater effect on the skin panel when it is already thermally and aerodynamically loaded. The panel is more structurally compromised for energy pulses of long duration, of higher magnitude and/or applied at times of strong aerodynamic loading.
The experimental technique builds on existing electro-resistive heating techniques used for wind tunnel testing. Parametric studies were conducted to understand the design space and determine optimal panel thicknesses and direct-current application to maximise thermal-structural effects. A method to measure the induced thermal strain using digital image correlation was developed. To validate the experimental technique, a model with a 120mm by 80mm graphite panel with varying thicknesses was designed and tested on the bench. For the thinnest available plate, and a direct-current power supply of 350A material failure was not observed. Finite element modelling of the experimental conditions was conducted. Recorded temperatures were approximately within 9% of simulated results. Measured thermal strain was within 0.05% of simulated material.
