Scaling and dynamics of impacts into cornstarch and water suspensions

Impacts into dense suspensions, which consist of micron-scale particles suspended in a Newtonian fluid, undergo a dramatic solidification when subjected to sudden impact. Recent work has shown that the forces during the initial moments of impact are too large to be described by discontinuous shear thickening (DST), which is a steady-state description. Other descriptions, such as the added mass model proposed by Waitukaitis and Jaeger, capture some aspects of the dynamics well but fail to predict certain features. Here, we show results from experimental impacts into dense suspensions consisting of cornstarch particles and water. We vary the size, speed, mass, and shape of the projectile as well as the density of the suspension. We quantify the forces as a function of time using high-speed imaging and other sensors. We use scaling analysis to probe the underlying physical mechanisms and compare our results to existing descriptions.