A Method for Measuring KIc at Very High Strain Rates

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Abstract
A method for determining the plane-strain fracture-toughness KIc of a material at very high strain rates is described and demonstrated on a tough polycarbonate. Tritensile stresses were produced within several tenths of a microsecond in the interior of a small cylindrical specimen by flat-plate impact with a gas gun. A number of previously introduced internal cracks of known size distribution were propagated by the tensile stress resulting from the intersection of rarefaction waves; smaller cracks were not activated. A critical stress intensity factor was calculated from the value of the tensile stress and the critical crack size. The relationship of this value to the plane-strain fracture toughness associated with the artest of a running crack is discussed.