Mechanical properties of 3D-printed continuous fiber-reinforced polymer reinforcing bars

The traditional pultrusion process for manufacturing fiber-reinforced polymer (FRP) reinforcing bars has several drawbacks, including high labor demands, mold dependency, material waste and end-of-use environmental concerns. To this end, 3D-printed continuous fiber reinforced polymers (3DP-CFRP) bars involving thermoplastic epoxy and additive manufacturing technique have been developed in this study. Comprehensive experimental studies, including tensile, transverse shear, and interlaminar shear tests, were conducted on 3DP-CFRP bars. The parameters explored included bar diameters of 3 mm, 4 mm, and 5 mm, and fiber contents of 22.6 %, 27.6 %, and 32.6 %. The test results reveal that the 3DP-CFRP bars with a fiber volume content of 32.6 % exhibit a tensile strength exceeding 800 MPa and an elastic modulus above 70 GPa. Transverse shear test results show the ratio of shear strength over tensile strength is approximately 1:6. Scanning electron microscope (SEM) and X-ray computed tomography (CT) were employed to characterize the microstructure of 3DP-CFRP bars. CT analysis demonstrates that increased bar diameter and higher fiber content both contribute to a greater porosity, consequently leading to decreases in tensile strength and interlaminar shear strength. Based on these porosity characteristics, relationships were established correlating bar diameter to tensile strength and fiber content to interlaminar shear strength. Collectively, the results provide valuable insights into the mechanical performance and microstructure of 3DP-CFRP bars, supporting their potential use in digital, recyclable, and high-performance construction applications.