Date of Award

9-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Aeronautics and Astronautics

First Advisor

Anthony N. Palazotto, PhD

Abstract

Several additively manufactured lattice designs and configurations were evaluated under compression loads under various strain rates from quasi-static to highly dynamic. These experiments examined how the mechanical behavior of the lattice changed based on the lattice design properties and the applied strain rates. The modulus of elasticity, yield strength, plateau stress, and toughness were observed to decrease with an increase in strain rate, revealing that the lattice designs exhibit a negative strain rate sensitivity. A new lattice flow stress model was developed to account for the mechanical response of the lattice and was incorporated into a computational model for simulation. The new constitutive model was evaluated across a broad range of strain rates, closely matching the results from the quasi-static, Split Hopkinson Pressure Bar, and Taylor Impact tests. Experimental impact and simulation results indicated that a lattice core embedded within a projectile would decrease the effects of impact wave propagation. However, the decrease in mass due to the lattice section would negatively influence the projectile's penetration depth.

AFIT Designator

AFIT-ENY-DS-21-S-107

DTIC Accession Number

AD1148774

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