Facile fabrication of hierarchically structured PBO-Ni(OH)2/NiOOH fibers for enhancing interfacial strength in PBO fiber/epoxy resin composites

Abstract A new hierarchical reinforcement was fabricated by depositing honeycomb-like Ni(OH)2/NiOOH coating onto poly(p-phenylene benzobisoxazole) (PBO) fibers using a facile chemical bath deposition (CBD) method. The crystal structure of Ni(OH)2/NiOOH deposited PBO fiber, denoted as PBO-Ni(OH)2/NiOOH, was characterized by X-ray diffractometer (XRD). Scanning electron microscopy (SEM) was employed to characterize the surface morphologies of PBO fibers and the de-bonding surface morphologies of their composites. Atomic force microscopy (AFM) and contact angle (CA) testing results demonstrated that the surface roughness (Ra) and wettability of PBO fibers increased obviously after Ni(OH)2/NiOOH deposition due to the unique honeycomb structure of the coating. Monofilament pull-out tests showed that the interfacial shear strength (IFSS) of PBO/epoxy composite increased by 46.3%. Moreover, the possible interfacial property enhancing reasons were explored. Thermogravimetric analysis (TGA) and hydrothermal aging tests revealed that PBO-Ni(OH)2/NiOOH had excellent thermal stability and hydrothermal aging resistance. Notably, the Ni(OH)2/NiOOH coating on the fiber surface can be easily reduced to Ni, resulting in a highly conductive PBO fiber. Our design starts from simple chemistry and inexpensive materials, and may offer a versatile and scalable method for fabricating hierarchical reinforcements.