Novel fiber-reinforced polymer tube connection mechanism utilizing NiTi shape memory alloy

Fiber-reinforced polymer (FRP) is extensively utilized in bridge engineering and aerospace due to their high specific strength-to-stiffness ratio. However, challenges in connecting composite materials with metals restrict their broader application. To address the limitations of existing composite tube connection mechanisms, this study proposes a novel mechanism of composite tube connection utilizing NiTi shape memory alloy (SMA) to apply a preload force. The proposed connection mechanism consisted of three components: an internal steel tube, a composite tube, and an external tube made of NiTi SMA. Preload was applied to the composite tube through the shape memory effect of unidirectional NiTi alloy, which enhanced interfacial friction and improved load-bearing capacity. This study presents a systematic investigation of preload and load-bearing capacity of this connection mechanism. Additionally, a finite element model (FEM) was developed in computational multiphysics solutions (COMSOL) to analyze the preload distribution at the chamfer of the NiTi SMA tube. The proposed technique shows favorable mechanical properties of joint assembly which were tested by uniaxial compression tests, and therefore, it can be extensively applied in the engineering field.