Influence of impact angle on size distribution of fragments in hypervelocity impacts

•Cumulative number of fragments as a function of fragment length and projected area decreased with increasing impact angle.•When the cumulative number on the vertical axis was divided by the normal component of impact velocity raised to the power 1.5, mater curves with respect to fragment length and projected area were proposed using a bilinear exponential distribution function.•The effects of impact angle on the crater shape and the indentation patterns on the witness plates were compared with that of cumulative number of fragment length and projected area of fragments. When aluminum alloy 2017-T4 spheres strike thick aluminum alloy 6061-T6 targets at 4 km/s, the size of fragments collected from a test chamber was measured and the effects of impact angle on the size and projected area of the fragments were examined. Impact angle clearly affected the size distribution and projected area distribution of the fragments. The cumulative number of fragments as a function of fragment length and projected area was proportional to the normal component of the impact velocity raised to the power 1.5. When the cumulative number on the vertical axis was divided by the normal component of the impact velocity raised to the power 1.5, experimental formulas with respect to fragment length and projected area were proposed using a bilinear exponential distribution function. The crater shapes on the targets were also examined, as were the area and shape of the indentations created by fragment particles on the witness plate. Their relationship to fragment size distribution was discussed. These results will assist in the revision of ISO 11227 with respect to oblique impact conditions.