Impact-activated solidification of dense suspensions via dynamic jamming fronts

Abstract

Although liquids typically flow around intruding objects, a counterintuitive phenomenon occurs in dense suspensions of micrometre-sized particles: they become liquid-like when perturbed lightly, but harden when driven strongly. Rheological experiments have investigated how such thickening arises under shear, and linked it to hydrodynamic interactions or granular dilation. However, neither of these mechanisms alone can explain the ability of suspensions to generate very large, positive normal stresses under impact. To illustrate the phenomenon, such stresses can be large enough to allow a person to run across a suspension without sinking, and far exceed the upper limit observed under shear or extension. Here we show that these stresses originate from an impact-generated solidification front that transforms an initially compressible particle matrix into a rapidly growing jammed region, ultimately leading to extraordinary amounts of momentum absorption. Using high-speed videography, embedded force sensing and X-ray imaging, we capture the detailed dynamics of this process as it decelerates a metal rod hitting a suspension of cornflour (cornstarch) in water. We develop a model for the dynamic solidification and its effect on the surrounding suspension that reproduces the observed behaviour quantitatively. Our findings suggest that prior interpretations of the impact resistance as dominated by shear thickening need to be revisited.

Dynamic response of shear thickening fluid under laser induced shock

“…Recently, shear thickening fluid (STF) is observed to show high energy absorption behavior through viscous dissipation during shear deformation. [8][9][10][11] More important, the energy absorption process of STF is observed to be reversible. 8,12,13 It has been regarded as a kind of advanced materials for designing composite materials and structures with high impact resistance.…”

“…The shear thickening behavior is observed to be result of particles rearrangement from an ordered state to a disordered state, e.g., formation of jamming particle clusters. 8,11 The viscosity recovers rapidly when the shear loading is removed. 11 Due to the excellent energy absorption behavior STF has founded applications in variety of fields such as damping, 14 armor, [15][16][17][18] to name a few.…”

“…Also, the deformation or crack of the hard-sphere particles as well as the volume compressibility of the particles and the polyethylene glycol could be neglected. In addition, the previous studies 8,19,[27][28][29][30] showed that critical conditions were required to occur the shear thickening in STF. A minimum strain might be not obtained in several tens of nanoseconds to occur the shear thickening behavior when the particle velocity decays to a relative low value, leading to the saturations of the stress attenuation and the energy absorption in the STF.…”

Colloidal crystals and water: Perspectives on liquid–solid nanoscale phenomena in wet particulate media

“…This is an important aspect in many practical issues, from impact absorption to digging [191,192], and it is ultimately related to the effective viscosity of the system in response to stress. In wet particulate media, capillary bridges play a central role since they not only generate friction and viscous forces but also their rupture and reformation during strain is a hysteretic, dissipative process [154,157].…”

Shear shocks in fragile networks

“…Fragility and the incipient nonlinear behavior is a collective phenomenon triggered by the mean global topology of the network that is composed of unbreakable Hookean springs (no smooth deformation can change z; springs must be added or removed). By contrast, in granular media, additional and crucial nonlinearities are typically introduced also at the local level, e.g., by the Hertzian interaction between grains or particle rearrangements that leads to a distinct shock phenomenology (9)(10)(11)(12)(13)(14).…”