Indentation, penetration and perforation of composite laminates and sandwich panels under quasi-static and projectile loading

The results of penetration and perforation tests carried out on composite laminates and sandwich panels using flat-faced, hemispherical-ended and conical-nosed indenters/projectiles under quasi-static, drop-weight and ballistic impact conditions with impact velocities up to 305m/s are reported. Load-displacement characteristics under quasi-static loading are presented and the energies corresponding to different degrees of damage are calculated. Fracture patterns observed in sandwich panels loaded dynamically are compared with those observed in identical panels under quasi-static loading. Ballistic limits and perforation energies are determined and a classification of the responses is deduced from the test data. Ways of improving the penetration resistance of the sandwich panels are also investigated. Simple theoretical analyses using multiple-spring models are developed to predict the quasi-static top skin failure load and the energy absorbed for sandwich panels. Failure maps are then constructed for sandwich panels loaded quasi-statically by flat-faced punches. Finally, empirical formulae that predict the penetration and perforation energies of FRP laminates and sandwich panels with such , laminates as skins and with foam cores under quasi-static and dynamic loading conditions are derived for hemispherical-ended indenters/projectiles. It is shown that the model predictions are in good correlation with the available experimental data. It is also shown that, to a first approximation, the empirical formula obtained for hemispherical-ended projectiles is also applicable to conical-nosed missiles.