Akimitsu Okura

The influence of the heat-treatment temperature on the crack-growth-resistance of a fine-grained carbon

Fine-grained carbons are generally regarded as “brittle” although an R-curve behaviour is predicted theoretically and toughening mechanisms are detected by the in-situ observation of the fracture process. The influence of the heat-treatment temperature, preferred grain orientation and the microstructure upon the fracture behaviour is examined. The results are compared with the theoretical considerations and literature data.

The Influence of the Network of Microcracks Upon the Crack Propagation Behavior Inside of Transparent Zirconia

The fracture process in many ceramics is rather complicated and still subject of scientific research. The aim is to unveil fracture processes on micromechanic scale and to develop techniques, based on this knowledge, for the manufacture of ceramics with enhanced toughness.

The Anisotropy of the Crack Growth Resistance of Unidirectional Carbon-Fibre/Carbon-Matrix Composites

The growth of cracks within an unidirectional C/C-composite and within the carbon-matrix is examined. In the first order the crack growth resistance depends on the orientation of the cracks towards the reinforcement. Parameters like fibre volume content and heat treatment temperature are of second order. The point of crack initiation at the tip of an artificial notch is dominated by thermal matrix pre-stresses. The R-curve concept is applied for the describtion of the fracture behaviour. The shape of the R-curve is closely correlated to the micro-failure processes acting during crack propagation.