Carbon Fibre Reinforced Polymer Composite Retrofitted Steel Profiles Using Automated Fibre Placement

Traditional methods for repairing impaired structures such as concreting, steel jackets, or timber splicing are impractical because of the inherent constraints associated with these materials. They would be susceptible to the same deterioration as the existing structure, leading to an ongoing cycle of repairs. Fibre-reinforced polymer (FRP) composite jackets offer a wide range of advantages including superior corrosion resistance, lightweight properties, and long-lasting durability. These characteristics make FRP composite jackets highly advantageous compared to conventional repair systems. Additionally, they can be effectively utilized for repairing various types of structures, including those made of timber, steel, and concrete. FRP composite jackets can be implemented through several techniques. However, in the experimental investigation presented in this chapter, automated fibre placement (AFP) was used to overwrap and reinforce two sets of thin-walled square hollow sections (SHS), columns and beams, with thermoplastic carbon fibre reinforced polymer (CFRP). The results obtained were then compared with the control samples without CFRP reinforcement. For the control columns, a good agreement was observed between the predicted and experimental ultimate compressive loads. The ultimate loads of CFRP reinforced columns exceeded the ultimate loads of the control columns. Inward and outward buckling was observed in each column. De-bonding, tearing, and snapping of the CFRP plies was observed in column specimens with thermoplastic CFRP reinforcement. For the control beams, there was a comparable agreement between the predicted ultimate load and the experimental ultimate load. It was found that the ultimate loads for some strengthened beams were higher than that of the control beams. For all beams, there was inward deformation on the upper surface of each beam, and outward deformations were observed on the two side walls of the SHS beams. This experimental investigation showed that the current strengthening processes using AFP is not comparable to traditional CFRP strengthening methods which use epoxy and FRP plies and that further research is required in this space. Due to the failure modes observed, future research is planned to improve the reinforcement method using AFP. The planned improvements are surface preparation, AFP processing conditions, number of CFRP layers and orientation of the CFRP.