Dr. Jeffrey Lloyd
Armor Mechanisms Branch, Terminal Effects Division
Army Research Laboratory

Metastructures and Metallurgy – Methods for dissipating large-amplitude, transient loads

ABSTRACT: In this talk, models and experiments are used to understand how non-fully dense metastructures can be used to mitigate shock waves that occur during impact and blast loading events. Several candidate metastructures are fabricated via 3d metal printing and tested using time- and spatially-resolved, subscale experimentation. In many use cases, large loading amplitudes of interest crush or destroy non-fully dense structures, negating their beneficial properties such as high specific energy absorption and stiffness. To address these shortcomings, a novel alternative approach is presented, whereby high-pressure phase transformations are utilized to manipulate shock waves. Composition and processing history dictate the transformation behavior. Therefore, ordered gradients in metallurgical properties can be fabricated to achieve desired dynamic behavior. Development of this new class of metallurgical metamaterials for high-pressure, transient phenomena appears to address many shortcomings of existing approaches that utilize architected, non-fully dense structures, but is still in its nascent stages of development.

BIOGRAPHY: Dr. Jeffrey Lloyd received his undergraduate and graduate degrees at Georgia Tech in 2008, 2010, and 2014 under the advisement of Dr. David McDowell. During this time, he received the NSF Graduate Research Fellowship, DOD SMART Fellowship, and Georgia Tech President’s Fellowship, and won a gold medal at the Army Research Laboratory 2012 graduate student symposium. Since graduating in 2014, Dr. Lloyd has served as a scientist at the Army Research Laboratory in the Impact Physics and Armor Mechanics branches. His research has focused on building computer models of microscale behavior that are used to engineer new materials and structures for the extreme dynamic loading environments, which occur in Army applications. His models have been used to describe and improve the high-rate properties and performance of magnesium, aluminum, titanium, steel, and high entropy alloys. Due to the multi-disciplinary nature of his work, Dr. Lloyd leads many internal and external research collaborations in order to design, fabricate, and test new materials and structures for extreme loading applications.