  We experimentally characterize the impact response of concentrated
suspensions of cornstarch and water. We hypothesize that the dynamically jammed
region that propagates ahead of the impactor is responsible for the strong
stress response to impact when it spans between solid boundaries. Using surface
imaging and particle tracking at the boundary opposite the impactor, we
observed that a visible structure and particle flow at the boundary occur with
a delay after impact. We show the delay time is about the same time as the the
strong stress response, confirming that the strong stress response results from
deformation of the dynamically jammed structure once it spans between the
impactor and a solid boundary. A characterization of this strong stress
response is reported in a companion paper (arXiv:1407.0719). We also elaborate
on the structure of the dynamically jammed region once it spans from the
impactor to a solid boundary. We observed particle flow in the outer part of
the dynamically jammed region at the bottom boundary, with a net transverse
displacement of up to about 5\% of the impactor displacement, indicating shear
at the boundary. Direct imaging of the surface of the outer part of the
dynamically jammed region reveals a change in surface structure that appears
the same as the result of dilation in other cornstarch suspensions. Imaging
also reveals cracks, like a brittle solid. These observations suggest the
dynamically jammed structure can temporarily support stress according to an
effective modulus, like a soil or dense granular material, along a network of
frictional contacts between the impactor and solid boundary.
