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Abstract

Controlling the interplay between small-scale properties and large-scale mechanical behavior is a fundamental problem in materials science, one that is at the cornerstone of all materials processing. A large body of work has been applied to reliably testing and modeling material properties on sub-micron length scales, and modern fabrication techniques have enabled the creation of precise micro- and nanoscale architectures. The current challenge lies in understanding how the coupling of nanomaterials and architecture can give rise to new properties in bulk materials.

This talk will focus on two distinct classes of micro- and nanoarchitected materials: nanolattices and 3D CFRP composites. Hollow ceramic nanolattices with wall thicknesses down to 10nm were fabricated using a combination of atomic layer deposition and two-photon lithography. It was found that the Al2O3 nanoceramics used had high tensile strengths on the order of 2GPa, which enabled the activation of shell buckling instabilities in the nanolattice walls and subsequently led to the creation of highly deformable and recoverable ceramic metamaterials. The addition of hierarchical design to nanolattices is found to greatly enhance their strength and recoverability via the localization of failure to multiple discrete length scales. The strength and stiffness of nanolattices deviates significantly from classically predicted lattice scaling relationships, and this is examined through a study of four different nanolattice topologies across a range of relative densities and structural parameters.

The mechanical performance of 3D woven carbon fiber reinforced polymer (CFRP) composites is examined experimentally and numerically. 3D CFRPs demonstrate exceptional shear and compression hardening and ductility, far exceeding that of traditional laminated composites. Crystal plasticity based numerical models are used to uncover how the 3D architecture leads to a ‘shear trapping’ effect, both allowing for the build-up of higher stresses in the composite and inhibiting the propagation of compressive microbuckling events. These results demonstrate that the micromechanical properties of the composites, specifically the plasticity mechanisms of the fiber bundles, are critical to understanding bulk material behavior

Bio

Lucas is a Research Associate at the University of Cambridge studying the micromechanics of 3D woven composite materials with Prof. Vikram Deshpande. He completed his Ph.D. at the California Institute of Technology (Caltech) under the guidance of Prof. Julia Greer, where he worked on research studying the mechanical properties of 3D nanoarchitected materials. His research interests center around studying material properties at fundamental length scales and using that knowledge to inform the design of new materials with exceptional properties.

Date/Time:
Date(s) - Feb 15, 2018
11:00 am - 12:00 pm

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