Interfacial bond–slip performances of CFRP tube-ultralightweight cement composite-stainless steel tubular pipe

Abstract

This paper introduces a novel solution for marine structures facing harsh environmental conditions—a CFRP tube-ultralightweight cement composite (ULCC)-stainless steel tube tubular pipe. ULCC plays a crucial role in significantly reducing the self-weight of the pipe without compromising its mechanical performance. The study mainly focuses on investigating the bond–slip behavior between ULCC and stainless steel tube, as well as between ULCC and CFRP tube, considering a range of bond lengths, tube diameters, and tube thicknesses. To gain insight into this behavior, the distribution of strain and stress within the stainless-steel tube and CFRP tube was effectively measured using optical fiber sensors and digital imaging correlation techniques. The findings reveal that increasing tube diameter can lead to a reduction of 69.8% and 70.3% on ultimate bond strengths for stainless steel tube and CFRP tube, respectively. Conversely, increasing the thickness of the stainless-steel tube leads to a reduction of 56.9% in ultimate bond strength, while the bond strength between CFRP tube and ULCC benefits from CFRP tube thickness (61.0% improvement). Increasing bond length can reduce the bond strengths. Empirical equations have been provided to facilitate the calculation of average and local bond strengths based on bond length, tube diameter, and thickness. Additionally, constitutive models have been developed to accurately represent the bond–slip behavior of stainless-steel tube-ULCC and CFRP tube-ULCC specimens. Understanding the bond behaviors of CFRP-ULCC-stainless tubular pipe allows for enhanced load transfer mechanism and composite action, and optimized structural design.