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To improve the interfacial properties between carbon fibers (CFs) and polycarbonate (PC) resin, multi-walled carbon nanotubes (MWCNTs) were deposited onto desized CF surfaces using an ultrasonic-assisted electrophoretic deposition method, forming a multi-scaled hierarchical structure. The results showed that morphologies and geometrical structures of the as-prepared hierarchical structures could be readily tailored by varying in length and concentration of the CNT suspension. The optimum conditions were determined to be CNT length of 1-5 μm with suspension concentration of 0.5–1 wt%. A post-treatment, in combination of a polymer binder and laser irradiation, was followed to solidify the morphology and geometry of the CNT network structures formed by the CNTs with length 1-5 μm, which allowed a 22.9% ± 1.6% improvement in the interfacial bonding strength than that without the post-treatment and 68.1% ± 2.3% improvement than bare CF, evaluated by a single-filament fragmentation test. It was the well-defined CNT porous network structures that are favorable for thermoplastic resin infiltration through channels for resin flow and capillary action, thus enhancing the composite interfacial properties. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Long CNTs can be homogeneously coated on CF surface to form porous networks. • The epoxy serves as a local "welder" by the laser heating. • The networks were favourable for high-viscosity resin infiltration. • CNT/CF hybrids could afford a significantly higher interfacial bonding strength. • This method can be developed as a facile, scalable and cost-effective approach. Abstract A facile method to prepare carbon nanotube/carbon fiber hybrid fiber was explored by an intermittent ultrasonic-directed electrophoretic deposition, and a following laser transient heating was used for welding the deposited carbon nanotubes on carbon fibers at joints. The formed porous networks were favourable for resin infiltration, leading a significant increase in interfacial bonding strength of carbon fiber reinforced polycarbonate composites. [ABSTRACT FROM AUTHOR]

To reveal the interfacial adhesion nature between a carbon fiber (CF) and its surrounding polycarbonate (PC) matrix, the carbon fibers were electrochemically oxidized to differentiate the surface roughness and chemistry status. The fiber surfaces were characterized by SEM, XPS, AFM and dynamic contact angle measurements. Both surface-coating and hot-pressing methods were adopted to prepare specimens for evaluating the CF/PC interfacial adhesion properties by single-filament fragmentation tests. The surface-coating method gave a relatively weak interfacial shear strength (IFSS) result, which varied almost monotonously with the fiber surface roughness, suggesting that in this case the interfacial properties should be dominated by a mechanical interlocking mechanism. However, the hot-pressing process gave a 46–81% higher IFSS result than the solution-coating one, and the IFSS data increased almost linearly with polar component of the carbon fiber surface energy. It was very possible that the interfacial adhesion properties were largely controlled by the chemical reactions (e.g., ester-exchange reaction) at high temperature, which were easy to occur in the presence of oxygenated functionalities at CF surfaces. [ABSTRACT FROM AUTHOR]

The favorable interfacial properties of carbon fibers (CFs) and matrix are the key to the design and fabrication of a CF reinforced composite with superior micromechanical properties for various modern technological applications. However, high viscosity of a thermoplastic polymer makes resin infusion difficult, resulting in poor impregnation into CFs, ultimately leading to insufficient interfacial adhesion during composites fabrication process. Here the polycarbonate nanoparticles (PC-NPs) were pre-coated on the CFs from PC-NP aqueous solution and formed compact microstructure, which significantly improved the resin impregnation around CFs and interfacial adhesion between CFs and PC matrix. This PC-NP assisted CF/PC composite exhibits an increased interfacial shear strength up to 37.03 MPa, which is ~67.25% higher than that of un-coated CF/PC composite. Moreover, the tensile strength and flexural strength are enhanced remarkably by ~41.06% and ~22.16% increase, respectively. These results therefore demonstrate that the attachment of thermoplastic PC-NPs is a facile, environmental-friendly and viable approach in design and modification of the interfacial properties of CFs and PC matrix, which can be expanded for other multifunctional CF-reinforced composites with unique micromechanical properties for various practical applications. • A controlled attachment of PC-NPs on CF surface can be achieved by electrostatic attraction in the aqueous solution. • PC-NPs attachment to the CF surface leads to high resin impregnation and a desired interface between CFs and PC matrix. • PC-NP assisted CF/PC composites exhibit highly efficient interfacial adhesion and excellent mechanical properties. [ABSTRACT FROM AUTHOR]

To improve the interfacial properties between carbon fibers (CFs) and polycarbonate (PC) resin, the PC resin was pre-coated onto the CF surfaces by a spray-coating method, and a post-heating process was applied for ensuring uniformity of the coating layer. To further investigate the interfacial interactions between the CFs and the coating layers, the physically-adsorbed PC resins were removed from some coated CFs by washing with solvent. The results showed that the CF/PC interfacial adhesion properties could be related to the coating thickness (or the resin impregnation) and fiber-matrix interactions. For a PC coating layer thinner than 0.15 μm, the PC could not be fully-impregnated into the CF bundles, thus leading to inferior CF/PC interfacial properties and mechanical properties in the final composites; while for a coating layer with thickness ranging from 0.15 to 0.32 μm, it allowed formation of well-impregnated interfaces; if coupled with a further hot-pressing for strengthening the interfacial bonding interactions, both the CF/PC interfacial shear strength and mechanical properties for the corresponding composites were significantly enhanced. The interfacial interactions and reinforcing mechanisms for the CF/PC composites were schematically proposed. [ABSTRACT FROM AUTHOR]