Growing Carbon Nanotubes In Situ Surrounding Carbon Fiber Surface via Chemical Vapor Deposition to Reinforce Flexural Strength of Carbon Fiber Composites

This study employed novel joint treatments to strengthen the carbon fiber reinforced polymer (CFRP) composites. Vertically aligned carbon nanotubes (VACNTs) were prepared in situ on the catalyst-treated CF surface via the chemical vapor deposition (CVD) method, intertwining into three-dimensional fiber-nets and fully surrounding CF to form an integrated structure. The resin pre-coating (RPC) technique was further used to guide diluted epoxy resin (without hardener) to flow into nanoscale and submicron spaces to eliminate void defects at the root of VACNTs. Three-point bending testing results showed the growing CNTs and RPC-treated CFRP composites yielded the best flexural strength, a 27.1% improvement over the specimens without treatment, while the failure modes indicated that the original delamination failure was changed into flexural failure with through-the-thickness crack propagation. In brief, growing VACNTs and RPC on the CF surface enabled toughening of the epoxy adhesive layer, reducing potential void defects and constructing the integrated quasi-Z-directional fiber bridging at the CF/epoxy interface for stronger CFRP composites. Therefore, the joint treatments of growing VACNTs in situ via the CVD method and RPC technique are very effective and have great potential in manufacturing high-strength CFRP composites for aerospace applications.

Automated summary

This study used novel joint treatments to strengthen carbon fiber reinforced polymer (CFRP) composites. Vertically aligned carbon nanotubes (VACNTs) were grown in situ on the catalyst-treated CF surface using the chemical vapor deposition (CVD) method, forming an integrated structure. The resin pre-coating (RPC) technique was further employed to eliminate void defects and enhance the flexural strength of the CFRP composites. The results showed significant improvement in flexural strength and change in failure mode with the joint treatments.