The two-phase nature of a fiber-reinforced polymer gives rise to a multiplicity of possible failure modes [1,2]. The mode of failure depends not only upon the intrinsic fiber and resin properties, but also upon the interphase or interlaminar properties [3]. Thus we find that composite systems with essentially the same component, i.e., fiber and matrix, properties can exhibit different tensile [4], compressive [2], flexural [4], fatigue [5], and fracture [6] behaviors due to varying interlaminar properties.