Additively Manufactured Metallic Cellular Materials for Blast and Impact Mitigation
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Authors
Harris, Jonathan Andrew
Advisors
McShane, Graham
Date
2018-05-19Awarding Institution
University of Cambridge
Author Affiliation
Department of Engineering
Qualification
Doctor of Philosophy (PhD)
Language
English
Type
Thesis
Metadata
Show full item recordCitation
Harris, J. A. (2018). Additively Manufactured Metallic Cellular Materials for Blast and Impact Mitigation (Doctoral thesis). https://doi.org/10.17863/CAM.18766
Abstract
Selective laser melting (SLM) is an additive manufacturing process which enables the creation of
intricate components from high performance alloys. This facilitates the design and fabrication of
new cellular materials for blast and impact mitigation, where the performance is heavily influenced
by geometric and material sensitivities. Design of such materials requires an understanding of
the relationship between the additive manufacturing process and material properties at different
length scales: from the microstructure, to geometric feature rendition, to overall dynamic
performance. To date, there remain significant uncertainties about both the potential benefits
and pitfalls of using additive manufacturing processes to design and optimise cellular materials
for dynamic energy absorbing applications. This investigation focuses on the out-of-plane
compression of stainless steel cellular materials fabricated using SLM, and makes two specific
contributions. First, it demonstrates how the SLM process itself influences the characteristics
of these cellular materials across a range of length scales, and in turn, how this influences the
dynamic deformation. Secondly, it demonstrates how an additive manufacturing route can be
used to add geometric complexity to the cell architecture, creating a versatile basis for geometry
optimisation. Two design spaces are explored in this work: a conventional square honeycomb
hybridised with lattice walls, and an auxetic stacked-origami geometry, manufactured and tested
experimentally here for the first time. It is shown that the hybrid lattice-honeycomb geometry
outperformed the benchmark metallic square honeycomb in terms of energy absorption efficiency
in the intermediate impact velocity regime (approximately 100 m/s). In this regime, the collapse
is dominated by dynamic buckling effects, but wave propagation effects have yet to become
pronounced. By tailoring the fold angles of the stacked origami material, numerical simulations
illustrated how it can be optimised for specific impact velocity regimes between 10-150 m/s.
Practical design tools were then developed based on these results.
Keywords
Additive manufacturing, cellular materials, impact, blast, energy absorption, impact engineering, selective laser melting, origami, honeycomb, dynamic buckling, ABAQUS, Hopkinson bar, Kolsky bar, stainless steel
Sponsorship
AWE plc.
Embargo Lift Date
2100-01-01
Identifiers
This record's DOI: https://doi.org/10.17863/CAM.18766
Rights
No Creative Commons licence (All rights reserved)