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

Abstract

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 4×102 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.

An apparent viscosity function for shear thickening fluids

“…In contrast, for shear thickening fluids, in spite of the large body of literature devoted to microscopic models based on the Smoluchowski formalism [23][24][25], it is of common use to resort to the power-law model [26,27], given by Eq. (2)…”

Energy dissipation in concentrated monodisperse colloidal suspensions of silica particles in polyethylene glycol

“…Applications proposed towards these properties are integration in dampers [17,18], in structures such as skis to tailor both their damping and stiffness properties [11,19] and in personal protective equipment [20,21]. Flexible ballistic vests known as "liquid armour" [22][23][24] composed of Kevlar fabrics impregnated with STF have thus been proposed, as well as foam-impregnated STF pads for impact absorption [20,21].…”

Rate-activated strapping for improved retention of protective eyewear during impact

“…This behavior has been exploited in a number of smart material applications, including STFcontaining foams, beams, and dashpots [12][13][14][15]. More recently, STFs have been used to create flexible straps with rate-dependent properties [16,17].…”