This paper addresses the multi-scale simulation of heterogeneous materials with a special emphasis on the modeling of internal discontinuities. In a homogenization context the local material structure is discretized by the extended finite element method which uses an enriched displacement approximation in combination with a cohesive zone model. This approach is applied to predict the effective material behavior of a fiber reinforced polymer and is then used to investigate the interaction of the fiber-matrix interface with an adhesive layer. All simulations are validated by corresponding experimental data.