The mechanical behavior of thin sandwich beams with steel faces and porous polymer core have been investigated using quasistatic four-points bending. Classic sandwich models predicting the behavior and the failure modes are improved to fit the particular configuration of the structure. Numerical simulations were set up in order to investigate damage at large strain. Macroscopic results are compared with analytical models and numerical simulations. Two numerical models of the core allowed confrontation of local behavior with experiments. Criteria for localization and damaging depending on core architecture are proposed.