Novel ductile FRP system for concrete reinforcement: concept and experimental characterization

This paper presents a novel design concept for fiber reinforced polymer (FRP) composites consisting of three-dimensional (3D) printed cores and FRP helical skins as a means of ensuring adequate ductility, compared to the brittle FRP systems conventionally used for internal reinforcement. The experiment demonstrated that when the FRP skins were loaded in tension, the core—which was 3D printed using acrylonitrile butadiene styrene or polylactic acid—was gradually compressed, thereby leading to plastic deformation. This behavior ensured a nonlinear load response while eliminating the unfavorable brittle failure of the FRPs. The results also indicated that the proposed FRP composite system ensured that no premature debonding/delamination occurred between the skin–skin and skin–core. The results of the parametric experimental study indicated that design parameters such as the FRP amount, core height, core span, core shell thickness, core material, core brace, and core number (i.e., the number of inner cores used for the composite) may be optimized to realize the expected design load capacity and ductility.