Repair of Small-Area Delamination in Carbon Fiber-Reinforced Polymer through Small Drilled Hole and Carbon Nanotubes-Reinforced Resin Pre-Coating Technique

This study explores the potential for repairing small, isolated delamination areas in carbon fiber-reinforced polymer (CFRP), while preserving the integrity of the composite structures. A small drilled hole at the center of the delamination section served as a channel for the epoxy infill of the sharp delamination cracks. The pressureless infill repair was achieved through the capillary action of an acetone-diluted resin pre-coating (RPC) solution (without hardener) with CNT reinforcement, comprising 89 m/m% acetone, 10 m/m% resin, and 1 m/m% CNT. This acetone-rich resin pre-coating (RPC) solution is easily prepared and applied to the drilled hole area. Curing of the CNT-toughened resin infill was induced by filling the small drilled hole with a resin–hardener mixture toughened by CNT/aramid pulp. The effectiveness of the delamination repair was compared for curing periods of two weeks and three months. The flexural strength measurements indicated that a restoration level of 77% was achieved in this study, while the optimum 100% restoration was achieved using the same technique for edge delamination repairs.