Performance of the star-shaped flyer in the study of brittle materials: Three dimensional computer simulations and experimental observations

A three dimensional finite element computer simulation has been performed to assess the effects of release waves in normal impact soft-recovery experiments when a star-shaped flyer plate is used. Their effects on the monitored velocity-time profiles have been identified and ‘their implications in the interpretation of wave spreading and spa11 signal events highlighted. The calculation shows that the star-shaped flyer plate indeed minimizes the magnitude of edge effects. The major perturbation to the one-dimensional response within the central region of the target plate results from spherical waves emanating from the corners of the star-shaped plate. Experimental evidence of the development of a damage ring located in coincidence with the eight entrant corners of the flyer plate is reported. Microscopy studies performed in the intact recovered samples revealed that this damage ring eliminates undesired boundary release waves within the central region of the specimen. Consequently, the observed damage in compression and tension within this region can be attributed primarily to the conditions arising from a state of uniaxial strain.