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• Polymer-aluminum laminates on the strike-face of steel plates enhance ballistic performance.• With judicious selection of substrate and laminate, a broad range of performance and weight combinations can be obtained.• There is both a reduction in magnitude of the substrate deformation and spatial dispersion of the impact.• The main function of the metallic layers is to stiffen the polymer without affecting the latter's viscoelasticity response. A study was carried out of pressure wave transmission and the ballistic penetration of steel substrates incorporating a front-face laminate, the latter consisting of alternating layers of thin metal and a soft polymer; the latter undergoes a viscoelastic phase transition on impact. The ballistic properties of laminate/steel structures are substantially better than conventional military armor. This enhanced performance has three origins: large energy absorption by the viscoelastic polymer, a significant strain-hardening of the material, and lateral spreading of the impact force. These mechanisms, active only at high strain rates, depend on the chemical structure of the polymer but not on the particular metal used in the laminate. G R A P H I C A L A B S T R A C T a b s t r a c t a r t i c l e i n f oPublished by Elsevier Ltd.

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The properties of steel substrates coated with soft polymers were characterized, in order to assess their connection to ballistic properties. An impact-induced viscoelastic phase change of the polymer effects large energy dissipation, while also spreading the force over a wider area, which reduces the impact pressure. Both effects enhance the performance, as directly measured and seen from strain measurements on the substrate taken during ballistic tests. The contribution of the front-surface polymer to impact performance is increased for harder substrates, indicating a coupling of the layers related to impedance mismatching. Since this effect is very local, the phenomenon can be exploited by surface-hardening of the steel.