The Dynamic Compressive Response of an Open Cell Foam Impregnated with a Non-Newtonian Fluid

by Dawson, M., McKinley, G.H. and Gibson, L.J.

The response of a reticulated, elastomeric foam filled with colloidal
silica under dynamic compression is studied. Under compression beyond
local strain rates on the order of 1 s^{-1}, the non-Newtonian,
colloidal silica-based fluid undergoes dramatic shear thickening and
then proceeds to shear thinning. In this regime, the viscosity of the
fluid is large enough that the contribution of the foam and the
fluid-structure interaction to the stress response of the fluid-filled
foam can be neglected. An analytically tractable lubrication model for
the stress-strain response of a non-Newtonian fluid-filled,
reticulated, elastomeric foam under dynamic compression between two
parallel plates at varying instantaneous strain rates is developed. The
resulting lubrication model is applicable when the dimension of the
foam in the direction of fluid flow (radial) is much greater than that
in the direction of loading (axial). The model is found to describe
experimental data well for a range of radius to height ratios
(~1–4) and instantaneous strain rates of the foam (1 s^{-1} to 4x10^{2}s^{-1}).
The applicability of this model is discussed and the range of
instantaneous strain rates of the foam over which it is valid is
presented. Furthermore, the utility of this model is discussed with
respect to the design and development of energy absorption and blast
wave protection equipment.