A novel braiding method and impact behaviors of 3-D braided composite three-way integrated circular tubes

•Three-way braided circular tube was prepared on self-designed braiding machine.•A novel 3-D integral braiding method of ‘yarn-added, yarn-realigned’ was created.•Drop-weight axial compressive damages were tested and photographed.•Effect of braided structures on compressive behaviors was presented. 3-D braided composite three-way circular tubes are integrated seamless connected tubes used for high strength connecting joints. We developed a novel braiding method of ‘yarn-added, yarn realigned’ to prepare three-way tubular preforms. Low-velocity impact compressions (LVIC) along axial direction were conducted to find effects of branch length and braiding layers on impact damage with drop-weight tester, high-speed camera, Micro-CT and digital image correlation (DIC). It was found that the three-way braided tubes have uniform structure both at the branches and joint regions. There is shear band induced by the weakened interface appeared after the peak load and formed within 60 μs under impact. The ultimate strength was positively correlated with the impact energy and braiding layers, while negatively correlated with the branch tube length. The test results showed that the branch length affected the position of stress concentration, and the influence of braiding layers on the LVIC behaviors is more significant than that of the branch length.