Nobuo Ohtani

Dynamic Crack Propagation Associated with Inner Materials Degradation

The dynamic crack propagation in mode I tension in composites with and without inner fatigue-degradation is investigated. The composites in interest are GFRP and CFRP. The dynamic crack propagation velocity is measured by velocity gages and by the electric potential method. It is found that the inner materials degradation effect is conspicuous in GFRP, showing much lower crack propagation velocity for the degradated case, however, on the contrary, for CFRP, almost no difference is observed between those CFRP specimens with and without inner materials degradation due to fatigue, showing almost same crack propagation velocities close to the elastic theoretical crack velocity for both with and without fatigue degradated cases.

Loads and Crack Velocities During Dynamic Fracture

Behaviors of loads and crack velocities observed during dynamic fracture in metals and viscoelastic solids, especially viscoelastic features such as the initial slow crack growth and the strain rate dependent crack propagation velocity profiles, are presented in connection with the applied strain rates and temperatures. The newly devised velocity gauge method to measure the very initial slow crack growth in viscoelastic solids is also briefly described.