Transparent Impact-Resistant Composite Films with Bioinspired Hierarchical Structure.

Inspired by the helicoidally organized microstructure of stomatopods' smasher dactyl club, a type of impact-resistant composite film reinforced with periodic helicoidal nanofibers is designed and fabricated, which reproduces the structural complexity of the natural material. To periodically align nanofibers in a helicoidal structure, an electrospinning system is developed to better control the alignment of electrospun nanofibers. When the nanofiber scaffold is embedded in an epoxy matrix, the presence of a hierarchical structure allows the composite films to achieve properties well beyond their constituents. The composite film exhibits excellent optical transparency and mechanical properties, such as enhanced tensile strength, ductility, and defect tolerance. With elegant design mimicking nature's hierarchical structure at multilength scales, the composite films could effectively release the impact energy and greatly increase the impact resistance, suggesting that the transparent composite films are promising protective layers suitable for various applications.