CuNb composites were processed by high pressure torsion using specially designed disks consisting of a pre-defined number of single sector elements called multi-sector disks. By variation of the applied plastic strain the composite structure could be tuned ranging from relatively coarse multilayer structures to nanostructured laminates. In this first study the technique is introduced, the microstructural and hardness evolution of CuNb with varying strain is presented and a fracture toughness study of the finest composite structure showing good damage tolerance has been performed.