ABSTRACT: Fundamental understanding of mechanical behavior of materials under extreme
dynamic loading conditions is crucial for designing high-strength, lightweight, and
high-temperature resistant structures for applications such as hypersonics, high-speed
manufacturing, impact and blast of structures, and spacecraft shielding. Under extreme
conditions, materials not only exhibit a different mechanical, thermal, and failure response but
can also undergo microstructural changes, significantly altering their material properties. Thus,
the characterization of materials under extreme conditions of pressure and strain rate at various
length and time scales require novel diagnostic techniques. In the first part of the talk, the role of
solid-solid phase transformation on the dynamic strength behavior of iron is investigated on a
continuum scale using photonic Doppler laser interferometry. In the second part of the talk, the
integration of high-speed imaging (10 million frames/s) and full-field 3D velocity measurements
using digital image correlation under shock compression is discussed, enabling material
characterization across the mesoscopic-macroscopic spatial scales. The increased spatial and
temporal resolution allows, for the first time, to characterize the role of material heterogeneities
on shock structuring of particulate composites.

BIO: Dr. Vatsa Gandhi is the Ashby Postdoctoral Fellow at the University of Cambridge. He
received his Ph.D. in Aeronautics from California Institute of Technology (2023) where he was
awarded the Donald Coles Prize for the best design of experiments. He received a B.S. in
Aerospace Engineering from the University of Texas at Austin (2018), and an M.S. from Caltech
(2019). His doctoral research focused on the physics of shock-induced phase transformations,
dynamic strength of metals and glasses, and shock wave structuring in composites. Currently, his
research focuses on developing new techniques for in-situ material testing using x-rays to
characterize the rate-dependent physics and fracture of discrete architected solids. His awards
include first place in the 2022 Michael Sutton International Student Paper Competition of the
Society for Experimental Mechanics (SEM).