Design and fabrication of impact resistant metal materials under extreme strain rate conditions is of great importance, especially in the field of collision protection of satellites and spacecraft. As inspired by the ‘brick-and-mortar’ microstructure induced excellent impact resistance in natural nacre , coupling with extraordinary intrinsic impact resistance of graphene (Gr), in this work a nacre-inspired Gr/Cu nanocomposite is fabricated, and its anisotropic extreme strain rate (at a level of ∼10 8 /s) deformation behaviors are studied by using laser-induced microprojectile impact tests (up to a speed of ∼2.5 Km/s). Such extreme impact loading together with pinning effect of graphene can lead to highly stabilized high-density deformation twins and stacking faults at impact front even in the ultrafine grained Cu matrix. As the loading direction perpendicular to the composite layers, volume of severely-deformed region and the density of twinning and stacking faults at impact front is one third and half of that in the parallel impact direction, respectively. Such discrepancies indicate the capacity to dissipate impact energy in the perpendicular direction is ∼6 times higher than that of the parallel one, in spite of only ∼0.9 vol% graphene incorporated in the bio-inspired composites, evidencing architecture design plays an important role in impact resistance of materials under extreme dynamic conditions.
Dynamic deformations at extreme strain rates (>10 6 /s) are frequently encountered by metallic structural materials. According to continuum theory, increasing the modulus and thus speed of sound in metallic materials could lead to enhanced impact resistance, while such goals are difficult to achieve via conventional alloying methods. On the other hand, recent researches have revealed that carbon materials such as graphene have far larger in-plane speed of sound than metals and therefore are intrinsically impact resistant. In this work, graphene/copper (Gr/Cu) nanolaminates were fabricated by incorporating graphene into copper matrix, and its ballistic performance at extreme strain rates (∼3 × 10 7 /s) was quantified via laser-induced projectile impact tests (LIPITs). The specific energy dissipation of Gr/Cu nanolaminates is found to be 54 % higher than Cu. Post-mortem analysis revealed that graphene nanoinclusions could cause additional coordinative deformation in regions surrounding the perforation zone in Gr/Cu, leading to enhanced ballistic performance of Gr/Cu nanolaminates.
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