Session: 17-01-01: Research Posters

Paper Number: 148643

148643 - Mechanics of Architected Materials Across Length and Time Scales 

Ultralight architected materials enabled by advanced manufacturing techniques have previously achieved density-normalized strength and stiffness properties that are inaccessible to monolithic materials, but most of this work has focused on static loading while the mechanical properties of these metamaterials under extreme dynamic loading conditions has remained largely unexplored. Properties such as energy absorption and the ballistic limit of these materials are of high interest for protective applications since, at the macroscale, the benefit of architecture for impact mitigation has been demonstrated. Despite these promising results, limitations of current additive manufacturing processes at the macroscale have made thorough investigations of impact or dynamics both time- and cost-inefficient, particularly if separation of scales between the periodic building block and the impactor is required. As such, microscopic dynamic testing techniques are needed to enable rapid experimental iteration which could accelerate discovery of materials for these conditions. 

Here, we use two-photon lithography as a rapid prototyping technique for micro-architected lattice materials, to systematically study their response under two types of dynamic loading. We fabricate lattice architectures of different morphologies (i.e., kinematically rigid and non-rigid architectures), with beam diameters of ~1.5 μm and unit cells of 7.5 to 10 μm, and we qualitatively and quantitatively characterize their response to (a) laser ultrasound excitation and (b) microparticle impact. To characterize their effective dynamic elastic constants, we induce photoacoustic stimuli in a pump-probe scheme to dynamically excite elastic waves in the architected materials and thereby determine the dominant modal response using a common-path interferometric setup. We experimentally reconstruct partial dispersion relations of the 3D micro-architected materials and we validate this technique using a variety of 3D architectures along various crystallographic orientations. This exploration merges expertise from ultrafast optics and metamaterial mechanics, elucidating a potential path for iterative and robust characterization of metamaterials in a dynamic regime.

Additionally, we employ the laser-induced particle impact test (LIPIT) method to accelerate SiO2 microparticles to velocities of up to 800 m/s, and use ultra high-speed imaging of the impact process to measure impact energetics. We showcase the benefit of 3D architecture to serve as lightweight shielding materials, demonstrating superior energy absorption metrics than non-architected materials for the same mass-normalized impact conditions. We also present a dimensional analysis framework which provides predictive capabilities of the impact response of these materials, which may serve as guiding principles for the design of 3D architected materials across length scales. These results uncover an extreme-condition regime over which nano- and micro-architecture can enable the design of new generations of ultra-lightweight, impact-resistant materials. 

Presenting Author: Carlos Portela MIT

Presenting Author Biography: Carlos Portela is the d’Arbeloff Career Development Professor in Mechanical Engineering at MIT. Dr. Portela received his Ph.D. and M.S. in mechanical engineering from the California Institute of Technology, where he was given the Centennial Award for the best thesis in Mechanical and Civil Engineering. His current research lies at the intersection of materials science, mechanics, and nano-to-macro fabrication with the objective of designing and testing novel materials—with features spanning from nanometers to centimeters—that yield unprecedented mechanical and acoustic properties. Dr. Portela’s recent accomplishments have provided routes for fabrication of these so-called ‘nano-architected materials’ in scalable processes as well as testing nanomaterials in real-world conditions such as supersonic impact. Dr. Portela received the 2023 Spira Award for Excellence in Teaching at MIT, was recognized as an MIT TR Innovator Under 35 in 2022, and was a recipient of the 2022 NSF CAREER Award and the 2019 Gold Paper Award from the Society of Engineering Science (SES).

Authors:

Carlos Portela MIT