PhD Dissertation Final Oral Defense (September 2024)

Title of dissertation: Periodic Cellular Cores with Tailored Architectures for Improved Mechanical Properties

Name of Candidate: Omar Abdulhadi Al Osman

Name of supervisor: Dr. Maen Alkhader

Abstract:
Cellular solids, which include foams and lattice structures, exhibit uniquely high specific structural and thermal properties due to their porous structures, as well as their topological and morphological features. These properties make them attractive for various weight-sensitive applications in aerospace, automotive, and biomedical fields. This work aims to accelerate the use of cellular solids in engineering applications by enhancing their properties through tailoring their topological and morphological features. Multiple approaches were used in this work to enhance the mechanical and thermal properties of cellular solids. The first approach focused on coating metallic aluminum foams with copper to improve their properties. This research path employed both numerical and experimental techniques, including finite element analysis (FEA), electrodeposition, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and uniaxial quasi-static compression. Results showed that coating aluminum foam with 4% relative density with copper significantly enhances its stiffness and thermal conductivity. Improvements reaching 138% and 196% in stiffness and thermal conductivity were realized, respectively. Analytical models predicting the macroscopic stiffness, yield, and thermal conductivity of coated metallic foams were derived. These models are applicable to material systems other than the copper and aluminum system investigated, generalizing this work to assist engineers in designing hybrid coated metallic foams from a wide range of constituents compatible with electrodeposition. The second approach involved enhancing the mechanical properties of lattice structures by modifying their topology with sinusoidal perturbations. Numerical simulations were conducted to analyze the effects of these perturbations on the modified honeycomb's response to out-of-plane, in-plane, transverse shear, flexural loadings, and low-velocity impacts. Results showed that the sinusoidal perturbations can shift the failure mode from elastic buckling to yielding, increasing the peak load capacity by up to 28.5% under concentrated out-of-plane loads.

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