Bouligand-like structured CNT film with tunable impact performance through pitch angle and intertube interaction

The Bouligand structure, characterized by a helicoidal arrangement of fibers, is prevalent in arthropods. Leveraging the exceptional impact resistance inherent in this structure, mantis shrimp could effortlessly crack the shells of shellfish using their dactyl club. Drawing inspiration from this natural phenomenon, we propose a novel Bouligand-like structured carbon nanotube film (BCNF) that combines the Bouligand structure with super-strong one-dimensional carbon nanotubes (CNTs). Through systematic investigation via molecular dynamics simulations, we explore the impact resistance and energy dissipation properties of BCNF. Our results reveal that the impact behaviors under different velocities can be tuned by adjusting the pitch angle of BCNFs. At an impact velocity of 1 km/s, the projectile exhibits three typical phenomena after impact, including embedding in the film, bouncing back, and penetration. At an impact velocity of 2 km/s, all films are penetrated. Furthermore, to enhance the impact resistance of BCNF, we introduce intertube crosslinking bonds, forming a crosslinked Bouligand-like structured CNT film (CBCNF). The study demonstrates that crosslinking effectively modulates the energy dissipation mode of the film. With increasing crosslinking density, the predominant energy dissipation mode shifts from interface sliding and bending of the CNTs to the fracture and collapse of CNTs. This research provides valuable insights into the microstructure design of CNT-based films and offers theoretical guidance for their applications in impact protection.