The development of protective plates for military applications has shifted from single-layer plates with high hardness to ceramic/metal composite concepts in recent decades. The combination of the high hardness of the ceramic layer and the high toughness of the metal layer has made it possible to surpass single-layer concepts in terms of protective effect. The main disadvantage of these composites is their limited weldability, which disqualifies them for automotive applications. One approach to convert such concepts for civilian, lightly armoured vehicles are steel composite sheets made of two different steel alloys. The difficulty here is to find alloys that are chemically compatible and at the same time have optimal properties to achieve a high protective effect. The aim of this dissertation is to find concepts for new types of steel protection plates that will be used in the next generation of automotive armoured vehicles. In the first step, currently used single-layer protective plates were characterised both mechanically (tensile test, hardness measurement, charpy impact test) and ballistically. In the ballistic tests according to the VPAM guideline, positive results were achieved especially with the plates with high hardness at level 9 and with high ductility at level 10. These tests served as a benchmark for the subsequent tests with the steel composite sheets. For the individual layers of the composites, both low-alloy and high-alloy cold-work steels were combined with each other or with maraging steels. In small-scale preliminary tests on a deformation dilatometer, all composite sheets were successfully produced by means of diffusion bonding. The resulting carbon diffusion led to strong changes in the microstructure and carbide formation near the interface, which was characterised by means of electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). The subsequent large-scale production by hot isostatic pressing and rolling resulted in comparable changes and also in metallically bonded sheets. In the ballistic test with level 9, the low-alloy composite sheets in particular were able to outperform the single-layer protective sheets. The sheets with a high hardness and a low proportion of hard layer (25:75%) showed the best results. The high-alloy composite sheets could not outperform these results despite their higher alloy content. In order to understand the failure mechanisms during ballistic impact, the occurring adiabatic shear bands (ASB) were characterised by means of EBSD and nanoindentation. Most of the materials showed the grain refinement and hardening in areas of ASBs as described in literature. In contrast, both the maraging steel and austenitic areas of the composites showed lower hardness in the shear band. The targeted use of these materials could create multilayer composite plates that have a reduced susceptibility to failure by ASBs. In combination with the knowledge gained about the optimal sheet thickness ratios, this could lead to more efficient protective sheets for civilian automotive applications.