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Accession Number ADA570997
Title Auxetic Metamaterials under Direct Impact Loads in a Structural Health Monitoring Framework.
Publication Date Jan 2013
Media Count 26p
Personal Author A. Ghoshal B. Chamish C. Kittur J. Ayers T. Chen
Abstract Under direct impact from ballistic loads, acoustic waves typically propagate throughout a structural component causing damage to sensitive areas. For structures with intelligent embedded monitoring systems, such as mounted piezoelectric actuators, a direct impact between 150 200 m/s of small-caliber rounds has produced catastrophic results. This report focuses on redirecting acoustic waves using non-traditional structural configurations. The technical approach utilizes periodic and graded metamaterials (produced from auxetic cellular, lattice topology and material composition), which are lightweight and can be assembled for extreme anisotropy and phononic bandgaps, which can be exploited to alter the propagation path of high amplitude stress waves. This research focuses on the initial stage of understanding how to tailor periodic lattices for highly concentrated impact and blast loads, which generally produce a broadband frequency response and yield only partial bandgaps. Specific attention is given to square, hexagonal, re-entrant, and modified re- entrant topologies. As a baseline comparison, a solid aluminum plate is examined against uniform and graded re-entrant unit cell lattices. The plates are individually subjected to both in- and out-of-plane direct impact loading conditions of a 0.22-caliber fragment simulating projectile traveling at 300 m/s. A less than 10% marginal difference in peak stress amplitude exists between the loading conditions for a given single through-the-thickness unit cell.
Keywords Acoustic waves
Blast loads
Frequency response
Impact loads
Metal plates
Piezoelectric materials
Stress waves
Structural components

Source Agency Non Paid ADAS
NTIS Subject Category 79E - Detonations, Explosion Effects, & Ballistics
46A - Acoustics
Corporate Author Army Research Lab., Aberdeen Proving Ground, MD.
Document Type Technical report
Title Note Final rept. 1 Oct 2011-30 Sep 2012.
NTIS Issue Number 1315
Contract Number N/A

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