Impact Damage in Sandwich Composite Structures from Gas Gun Tests

Abstract

The presentation describes a gas gun test programme to study impact damage in novel composite sandwich structures with folded composite cores (foldcore). Results from a series of high velocity impact (HVI) tests on two foldcore sandwich composite curved shells are presented in detail. Two impact scenarios relevant to aircraft fuselage upper and lower panel structures are described. These include hail impact scenarios: hail on ground with large ice balls at low velocity; hail in flight with small ice balls at high velocity; and hard runway debris, simulated by steel cubes typically 10 mm in size at impact speeds in the range 50 – 100 m/s. The aim of the test programme was to determine the critical energies and velocities for a given projectile and test panel causing first damage on the outer skin, perforation of the outer skin, first damage on the inner skin and finally the complete perforation of the sandwich panel. These damage thresholds are presented for two foldcore panels, one with a thin outer CFRP skin, and one with a more conventional balanced sandwich panel with thicker outer CFRP skin. The role of skin and core properties and thicknesses on the critical damage thresholds are discussed.