The damage tolerance of various lay ups of thin carbon/epoxy laminates (1.6 2.2 mm thick) is examined by compression after impact (CAI) tests, using a new testing device which adapts to the thicknesses of the specimens and does not require tabs nor any modification of the specimen geometry. The compression stress state was not modified by the presence of the device, as was verified by numerical simulation. With this device, CAI tests were done of different carbon/epoxy laminate lay ups (quasi isotropic, cross ply and woven) and the values of the residual strength and the normalized residual strength of the laminates were obtained as a function of the impact energy. The woven laminate was found to offer the highest residual strength under all the impact energies, and the quasi isotropic laminate the least loss of normalized strength as the impact energy was raised.

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The effect of the adhesive layer, used to bond ceramic tiles to a metallic plate, on the ballistic behaviour of ceramic/metal mixed armours is analysed mathematically and experimentally. Two types of adhesives, polyurethane (soft adhesive) and rubber modified epoxy resin (rigid adhesive), and different thicknesses, are considered in the study. Numerical simulations were made of low calibre projectiles impacting on alumina tiles backed by an aluminium plate, using a commercial finite difference code. Full scale tests were carried out to check the influence of the adhesive. An engineering model was also developed to provide a preliminary design tool taking account of the influence of the adhesive.

a b s t r a c tThis work focuses on an experimental study of flexural after impact behaviour of glass/polyester compos ite beams. The influence of impact energy, beam width, and impactor nose geometry on the residual flex ural strength was evaluated. Two widths of plain woven laminate specimens were selected. For each specimen width, the geometries of two impactor noses (Charpy and hemispherical) were chosen to carry out impact tests using a three point bending device, so that four different test configurations were exe cuted. The residual flexural strength of damaged specimens, evaluated by quasi static three point bend ing tests, was found to depend on the extent of the damage, so that the residual flexural strength was lower in the specimens in which the damage reached the edges of the beam. For this reason, the residual strength was lower in specimens impacted with a Charpy nose impactor than in the specimens impacted with a hemispherical nose impactor. Analogously, the narrower specimens presented a lower residual flexural strength than did the wider ones.

In this study, the crush behaviour and the energy absorption capability of an aluminium honeycomb core is discussed. A three-dimensional finite-element model of a honeycomb-core structure was developed using the commercial code Abaqus. Flatwise and edgewise experimental compressive tests were made to validate the numerical model and good agreement was found between the experimental data and the numerical results. Virtual compressive tests varying the cell size, cell-wall thickness, and material properties were performed. The deformation mode, compressive core behaviour and its energy-absorption capacity were examined. The crushing parameters at in-plane directions were more affected by the variations of the characteristic core parameters; although, in general, increasing the cell-wall thickness and the yield stress of the aluminium alloy give higher crush loads, and therefore the absorbed energy increases.However, if the cell size increases, the energy-absorption capacity decreases.