Biological materials, such as bone, wood or skeletons of marine organisms are biological tissues with remarkable mechanical properties. They are constructed by a hierarchical principle and able to adapt to the mechanical requirements on all levels. Details on the deformation mechanisms can be determined by tensile testing and simultaneous synchrotron x-ray diffraction. This in-situ methodology allows following deformation processes at several levels of the tissues’ hierarchical structures. In tendon or bone, for example, it turns out that collagen fibrils are stretching more than the molecules they are composed of. The whole tissue stretches even more than the fibrils. This indicates a shear coupling between stiff fibrils mediated by a soft “glue” matrix. In wood, cellulose microfibrils are wound helically around the lumen of tube-like cells, which are shown to react to tension like elastic springs. Again, the stiff cellulose fibrils are shear coupled via a matrix, which in this case consists of hemicelluloses reinforced with lignin. This composite principle, where load between stiff particles or fibres is transferred through shear in a thin layer of soft matrix, seems to be a general feature in natural materials, conferring them both rigidity and toughness.

Vortragssprache: Englisch