Thermo-structural optimization of all-metallic prismatic sandwich panels.

摘要

All-metallic sandwich panels with prismatic cores offer tremendous potential for thermostructural applications, due to their exceptional bending response together with the possibility of driving a fluid through their open cores, thus enabling active cooling. This thesis offers a complete thermo-mechanical characterization of prismatic panels with both corrugated and diamond cores, with main emphasis on geometric optimization.; For the mechanical study, the panel geometry is analytically optimized for minimum weight under any combination of bending and transverse shear force. For longitudinal loadings (i.e. bending axis parallel to the core corrugation direction), corrugated panels show excellent performance, equivalent to the best concepts available; for transverse loadings (i.e. bending axis perpendicular to the corrugation direction), this goal is achieved with diamond core designs. Failure maps are constructed based on the analytical model to provide easy visualization of the failure modes and allow immediate identification of optimal designs. Such maps are used to design a selected number of experiments, with the three-fold goal of (i) validating the analytical model, (ii) exploring the behavior subsequent to failure initiation (thus assessing the robustness of the chosen designs), and (iii) check the reliability of numerical simulations in capturing limit loads and deformation modes. Good agreement is achieved among analytical, computational and experimental results.; In order to assess the active cooling performance of prismatic panels, a scenario is envisioned where a uniform heat flux is impinging on one face, with the rest of the panel being thermally insulated; under these conditions, all the heat flux is transferred to a cooling fluid flowing through the core channels. At any given level of the pressure drop, the panel geometry is optimized for maximum transferred heat flux subject to a temperature constraint on the structure. Although very large optimal core densities emerge (typically an order of magnitude higher than mechanical optima), good thermal performance can be achieved by much lighter structures; in particular, structurally optimized panels often show active cooling performance within a factor two of thermally optimized structures. This is a promising result for the design and fabrication of multi-functional plates.