Creating controllable three-dimensional microstructures on the surface of carbon fibers by manipulating ice crystallization to improve interfacial properties of composites

In nature, ice had a rich variety of shapes because of different growing conditions. Inspired by nature, we constructed controllable three-dimensional microstructures on the surface of carbon fibers (CFs) using water-based epoxy (WEP) by manipulating ice crystallization. The morphology of three-dimensional microstructures was tuned by manipulating the growth of ice crystallization. Briefly, the surface of CFs sized by WEP exhibited micro-spherical and layered morphologies after being treated by freeze-drying and unidirectional freeze-drying (bottom-up), respectively. The modified surface had ultra-high roughness, which could enhance the mechanical interlocking force between CFs and host matrix and improve the interfacial properties of composites. Furthermore, the resultant composites treated by unidirectional freeze-drying showed robust interfacial shear strength (72.27 MPa), which was increased by 60.18% compared to unmodified CFs. This strategy opened a feasible avenue for creating controllable three-dimensional structures on the surface of CFs.