Experimental investigation of wrapped composite X‐joints under uniaxial and multi‐axial loading conditions

Circular hollow section (CHS) multi‐membered structures, such as off‐shore wind turbine jackets and floating wind structures, face significant challenges under multiaxial loads. Wrapped composite joints have emerged as a promising alternative to conventional welded joints, offering superior structural and fatigue performance in previous pilot tests. This paper presents an experimental study on the failure mechanisms and load‐bearing capacity of wrapped composite joints under multi‐axial monotonic loading, using the Hexapod a six‐degree‐of‐freedom testing machine. The research question addressed in this study is to investigate the effectiveness of wrapped composite joints in resisting multi‐axial loads, and to understand the underlying failure modes. The experimental results demonstrate that the joints exhibit excellent resistance to uniaxial tension, uniaxial bending, and multi‐axial tension + bending loading, with failure modes including interfacial debonding, delamination, composite fracture, and steel yielding. Digital Image Correlation (DIC) and embedded optical fibers were used to monitor surface and interface strain. These findings suggest that wrapped composite joints offer significant resistance to multi‐axial loading.