Prestress Transfer and CFRP Damage Mechanisms in SMA ‐Prestressed Composite Tubular Joints: A Thermomechanical Finite Element Study

ABSTRACT Radial prestress is critical for frictional load transfer in composite–metal tubular joints, but its establishment in SMA‐prestressed systems is governed by coupled SMA recovery, interfacial contact transfer and the damage‐sensitive response of the CFRP tube. This study develops a sequential thermomechanical finite element model for an SMA‐prestressed composite tubular connection, incorporating SMA constrained recovery, contact interaction, metal elastoplasticity, and progressive CFRP damage. The model is validated using theoretical prestress predictions, inner‐sleeve circumferential strain, and axial tensile responses. Results show that the baseline SMA sleeve has only a limited through‐thickness temperature gradient; prestress establishment is instead dominated by reverse transformation, residual‐stress release, and constrained‐recovery stress generation. Because interfacial constraint delays reverse transformation, the stress‐free austenite finish temperature cannot be used alone to identify complete prestress establishment. Under high‐prestress conditions, increasing the SMA sleeve thickness or interference fit causes effective‐prestress saturation due to CFRP matrix‐compression damage and local softening, which reduce radial pressure‐transfer efficiency. The prestress‐induced initial damage further promotes fiber‐tension damage during axial loading and shifts the governing limitation from interfacial slip resistance to CFRP damage tolerance. These findings support damage‐controlled prestress design for SMA‐prestressed CFRP tubular joints.