Effect of Nanoscale Surface Modification on the Interfacial Mechanics of Carbon Fibers

Enhancing fiber surfaces through in situ growth of nanomaterials is known to improve fiber composite properties by enhancing the interface between the fiber and matrix. In this study, hydrothermal processes are used to achieve two types of interfacial modification for carbon fiber: zinc oxide nanowires (ZnO NWs) and nickel-based metal–organic frameworks (MOF). The interfacial strengths are evaluated using single fiber push-in tests via nanoindentation and the interfaces are analyzed through dynamic modulus-mapping. It is found that ZnO modification increases the interface strength by 9.40%, while MOF modification yields an even higher improvement of 16.34%. The load-displacement plots exhibit distinctive inflection points, elucidated through microstructural observations. Examining the modulus map of the interface region, a transition in the storage modulus from the fiber to the matrix is identified. A capillary flow-based model is developed to explain the resin penetration through nanoscale features. The findings reported here indicate that the timescale for resin absorption is significantly shorter than the curing timescales for the surface modifications explored in this study.