New Horizons in Microarchitectured Materials

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• Prof Norman Fleck, Cambridge University
• Wednesday 27 May 2020, 15:00-16:30
• Zoom Discussion https://harvard.zoom.us/j/271079684.

If you have a question about this talk, please contact Hilde Hambro.

YouTube Live https://ter.ps/EMLYouTubeLV

Microarchitectured materials possess a broad spectrum of mechanical, thermal and electrical properties due to their combination of topology, length scale and composition. Their topology ranges from closed cell 3D shell-structures (such as 3D foams) to open-cell lattices. Nodal connectivity has a major effect upon properties, and length scales can be at play in dictating strength and toughness when the cell size is reduced from metre-scale to nanoscale.

No strict bounds exist for the toughness of micro-architectured materials, and a high toughness can be achieved by the successive renucleation of fracture in the lattice ahead of a macroscopic crack tip. Likewise, there are no theoretical bounds for tensile ductility. Extreme properties, such as high strength are evident with a diminishing length scale, but new challenges (such low toughness) also appear. The advent of additive manufacture has opened up the opportunity of varying the topology and material choice within a shaped part. However, current manufacturing methods introduce defects into the cell walls that reduce the strength of the component. The sensitivity of strength to as-manufactured and as-designed defects are explored for an idealised lattice made by laser cutting. Additive manufacture also allows for the opportunity to tailor microstructure in order to give a stress versus strain curve upon demand.

In this talk the following research questions are addressed:

1. How can one design with microarchitectured materials? (How do we mitigate against stress raisers?)

2. What is the appropriate fracture mechanics methodology for these materials? (When does a crack tip J-field exist?)

3. What benefit can be obtained from inter-penetrating lattice materials? (What is the effect of the infiltration of an open-cell lattice by a second phase upon macroscopic properties?)

This talk is part of the Engineering - Mechanics and Materials Seminar Series series.

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