The Dynamic Fracture Toughness of Carbon-Carbon Composites

The dynamic fracture toughness of two types of carbon-carbon com posites (filament wound and felt substrate) and ATJ-S graphite was deter mined from instrumented Charpy impact tests. The resistance to crack initiation from a pre-existing flaw (notch) was examined by investigating the dynamic fracture toughness, KD , a linear elastic fracture mechanics parameter. The resistance to crack initiation and propagation was deter mined using the dynamic work-of-fracture parameter, γ fD . Testing was conducted over a range of impact velocities (4.0-202.8 in/sec), and the parameters KD and γ fD were found to be strongly sensitive to impact velocity for all three materials. As expected, the dynamic fracture tough ness of the highly anisotropic filament wound carbon-carbon composite was dependent on filament orientation.