High-rate deformation behavior and applications of fluid filled reticulated foams

The need for smarter and adaptive, energy absorption materials especially for human protection applications has fueled the interest in new and alternative energy absorbing composites. In this thesis a 'novel' energy absorbing fluid-composite that utilized a shear thickening fluid is developed. Shear-thickening fluids are a class of field responsive fluids that have the ability to transition from a low viscosity state to a high viscosity state under an imposed deformation field. A shear thickening fluid composed of silica monodisperse spherical particles of 0.3 ± 0.03 /anm diameter dispersed in ethylene glycol at volume fractions up to = 60% has been characterized. The behavior of the silica suspensions is studied under steady shear, small and large amplitude oscillatory shear flow and also in transient extensional flow. Oscillatory experiments indicate that both the onset and magnitude of the shear thickening depends on the frequency and strain applied and show that rapid time-varying deformations result in maximum energy dissipation. Two different regimes are observed in extensional flow measurement: at low extension rates the suspensions respond as a viscous rate-thinning fluid, whereas beyond a critical extension rate, the suspension strain-hardens and ultimately fractures in a solid-like fashion. Polyurethane open cell or 'reticulated' foam with a relative density of 0.03 and average cell size of 360 rpm is chosen to envelop the concentrated silica suspensions. The behavior of this nonlinear fluid-solid composite is studied over a range of filling fractions under quasi-static deformation rates (strain rates between 10-2 - 1 s-1), under dynamic impact loading (with energy densities of e = 105 - 106 J/m3) and under high strain-rate deformations (strain rates up to 800 s-').

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Mechanical Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Bettin, Giorgia

Advisor dc:contributor.advisor

• Gareth H. McKinley.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/42285

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/42285