The energy absorption and blast resistance of singly curved sandwich shells

Metallic sandwich panels with a cellular core, such as honeycomb or metal foam, can dissipate considerable energy through large plastic deformation under quasi-static or dynamic loading. The curved panels are generally substantially stronger and stiffer than other structural forms and perform better under various loadings. This is due to effectively supporting external loads by virtue of their spatial curvature. A better combination to leverage the advantages of shells and sandwich structures was expected and of great importance for its applications. Furthermore, recent research proved that the flat sandwich panels outperformed monolithic panels of an identical mass per area under blast and impact loadings. It is of great interests with a potential application to study the behaviour of curved sandwich structures under blast and impact loadings. To this end, the blast and impact response and energy absorbing performance of two types of cylindrical shells were investigated experimentally, numerically and analytically. Four different case studies to determine the energy absorption and blast and impact resistance performance of sandwich shells were conducted: (I) the lateral crushing of sandwich tubes compressed by two rigid plates; (II) radial crushing of sandwich tubes under inner blast loading, (III) indentation/penetration resistance of singly curved sandwich panels subjected to foam impact; and finally, (IV) mechanical response of singly curved sandwich panels subjected to blast loads. The deformation and failure patterns of sandwich shells were clarified under various loading conditions as well as the energy absorption mechanisms. Finite element models were developed and validated by these experiments, which provided more detailed deformation and failure information during the loading process. Importantly, these investigations found that: (I) the core crushing is an inherent deformation pattern for sandwich shells under various blast and impact loadings; (II) sandwich shell structures outperform their corresponding monolithic structures only in a certain range, determined by the intensity of blast and impact and the initial geometry features of the sandwich shells; (III) the glue effect between the core and face sheet plays an important role in curved sandwich structures and it is more important for curved sandwich structures with a thin face sheet than that with a thick face sheet; (IV) the strain rate or loading rate effect of the aluminium foam core is relatively small compared with other effects. Besides those findings, two analytical solutions were provided for sandwich tubes under lateral compression and inner blast loadings. Those solutions will enable designer to optimise the sandwich shell structures under blast and impact loadings, which will greatly enhance the blast and impact resistance of curved sandwich structures in various applications.