This work presents the results of a computational study that investigates the treatment of interfaces and its effect on the ballistic response of ceramics. Typical ceramic armor is comprised of a ceramic top plate bonded to a substrate. The objective of this work is to determine how much and under what conditions the numerical treatment of interfaces influences the results of a simplified impact calculation. Since different simulation frameworks resolve interfaces with different degrees of fidelity, it is important to understand the consequences of different numerical treatments. Here the Lagrangian code EPIC is used because the surfaces are explicitly defined, and the sliding and contact algorithms are robust and accurate. The approach uses a simple geometry whereby a tungsten carbide sphere impacts a target comprised of a ceramic top plate and an aluminum back plate. The target interface is computed using a perfect bond (the ceramic and aluminum share nodes) and no bond (the ceramic and aluminum do not share nodes so there is contact and sliding at the interface, friction is neglected). The ceramics investigated are silicon carbide and boron carbide. The silicon carbide is modeled using the Johnson-Holmquist-Beissel (JHB) ceramic model and the boron carbide is modeled using the Tonge-Ramesh (TR) ceramic model. The impact responses are assessed by comparing the damage in the ceramic, aluminum, and tungsten carbide sphere, including the back-surface displacement of the aluminum plate directly under the impact point. The use of cohesive elements is also discussed as a computationally efficient way to model interface bonding.