Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical Engineering

Committee Chair/Advisor

Dr. Garrett J. Pataky

Committee Member

Dr. Marian Kennedy

Committee Member

Dr. Fadi Abdeljawad

Committee Member

Dr. Suyi Li


Advances in additive manufacturing have enabled the creation of low density metamaterials with fine features and complex topographies. These new metamaterial topologies and size scales not previously possible broaden the spectrum of lightweight materials with unique properties that are advantageous in a variety of applications. There however is a lack of understanding of metamaterial failure and fracture behaviors. Studies tend to report only a few material properties rather than a comprehensive description of behavior. Due to this, there is a hesitancy to incorporate metamaterials into engineering designs despite proven remarkable properties. This work seeks to investigate in three parts the fracture and failure mechanisms controlling the deformation behavior of three different types of low-density metamaterials. The first part of the study explored increasing the fracture toughness of sheet-based metamaterials using designed porosity to redirect crack growth away from its original crack path to a less damaging direction. The crack was diverted into features in the metamaterial base topology, which served to toughen the material. It was identified that base material plays a role in the crack arrest mechanism activated. The added porosity was able to increase the fracture toughness of the metamaterial by a factor of three. The second part of the study calculated yield surfaces for common cellular material topologies that incorporates the anisotropy of tension, compression, and shear of cellular materials between different loading orientations. The shear component was the weakest of the topologies, atypical of monolithic material behavior. The third part of this study is currently on-going work to analyze the deformation of lattice metamaterials in compressive creep and compare the creep exponent and activation energy of the lattice to the base material as well as identify the mechanisms controlling the deformation of the lattice unit cell.



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