Fracture behavior of foam core composite sandwich Split Cantilever Beam (SCB) loaded in torsion was analyzed theoretically using the apparatus of linear-elastic fracture mechanics. A loading method is proposed to create two transverse forces of identical magnitude which load the beam in torsion. In this way, mixed-mode II/III crack loading conditions were induced. A three-dimensional finite element model was developed for simulating the mechanical response of the sandwich SCB. The strain energy release rate was used as a fracture characterizing parameter. The analysis by virtual crack closure technique revealed that the strain energy release rate mode components were distributed non-uniformly along the crack front through the width of the sandwich SCB. The relation between the fracture behavior and the sandwich core material was studied. For this purpose, three foam core composite sandwich SCB configurations (with three different rigid celullar foams used as core material) were simulated. It was found that the fracture behaviour of the sandwich beam can be improved by using foams with higher density as a core material. and Obsahuje seznam literatury