Damage properties of pre-embedded connection of carbon fiber wound composite tubes

Abstract

In this study, a new connection technology of composite tubes is proposed: carbon fiber (T700/TDE86) filament winding composite tubes with pre-embedded titanium alloy joints, which realize the application of light-weighting heavy load pod for a stratospheric airship. The axial tensile behavior of specimens was determined through experimental tests and by using finite element method. In comparison with the conventional bonding connection joints, the maximum failure load of specimens is higher than 105 kN, indicating the excellent mechanical properties of the novel connecting structure. Damage in the adhesive layer is caused by the opposite movement trend between the embedded titanium and the composite tube, and the main failure mode refers to the fiber tear damage. The ±30° layer near the ends of the titanium joint is subjected to a larger tensile load and is completely damaged because of the failure of the adhesive layer. Subsequently, the inter-layer reaches the ultimate failure strength, delamination takes place, and then the structure loses its loading capacity. Numerical simulation results of the progressive damage process and failure load are in good agreement with the experimental results. Stress analysis indicates that the failure of the adhesive layer is not the dominant factor that causes the structure to lose its load-bearing capacity. Moreover, structural strength is dominated by the tensile strength of the ±30° layers and the interlaminar shear strength between 90° layer and 30° layer. The circumferentially tightened 90° yarns in the grooves are also critical to the load-bearing effect of the structure.