Hierarchical toughening of bioinspired nacre-like hybrid carbon composite

Abstract Replicating the architecture of natural nacre has become an important approach for enhancing the damage tolerance of man-made materials. Nevertheless, this is principally limited to systems composed of chemically different constituents and demonstrates a difficulty in realizing structural hierarchy at multiple length-scales. Here a proof of concept is presented about the implementation of bioinspired nacre-like designs in a hybrid composite of pure carbon comprising its two basic allotropic forms, i.e., natural graphite flakes and amorphous carbon from the carbonization of organics. Multiscale micro/nano-architectures with three levels of hierarchy were constructed in the composite based on the preferential alignment of graphite flakes using bidirectional freeze casting method. The composite exhibited a remarkable mechanical efficiency, specifically featured by good damage tolerance with rising R-curve behavior, owing to the activation of hierarchical toughening mechanisms at micro to nano length-scales. This verifies the potency of nacre-inspired designs for generating enhanced fracture toughness in carbon systems, even using simple raw materials, which is significant for promoting their structural applications.