Distribution of axial yarns on the localized deformation and damage mechanism of triaxial braided composite tubes

Localized deformation and damage mechanism of triaxial braided composite tubes, with different quantities and positions of axial yarns, were experimentally studied under transverse low-velocity impact. A high-speed infrared thermography was applied to analyze the transient thermo-mechanical failure process and afterwards verified by the external and internal damage characterization. It is found that the distribution of axial yarns has a significant effect on the mechanical behavior of braided composite tubes. The bending stiffness and peak force of the tubes were enhanced with the increased quantity of axial yarns, while the impact lasting time and displacement presented an opposite trend. And the more axial yarns assembled at the impact side, the greater force oscillatory of the tubes under low-velocity impact, accompanied by the decreased heat generation in small-angle braided tubes and the alleviated fiber tows fracture, delamination and in-plane shear cracks inside the wall of large-angle braided tubes. On the premise of the same quantity of axial yarns, the position effect plays a key role. Axial yarns concentrated at the impact side could restrain the damages spreading to the non impact side by changing the damage mode of large-angle braided tubes. If a larger force is needed at the early stage, axial yarns could be inserted at the local position most probably to be impacted; Otherwise, it is highly suggested to braid at least one axial yarn in each layer at the impact side and non-impact side respectively to reinforce localized strength and prevent the impact-side indentation and non-impact-side delamination.

Automated summary

In this study, the localized deformation and damage mechanism of triaxial braided composite tubes were experimentally studied under transverse low-velocity impact with different quantities and positions of axial yarns. It was found that the distribution of axial yarns has a significant effect on the mechanical behavior of the tubes. Increasing the quantity of axial yarns enhanced the bending stiffness and peak force but decreased the impact lasting time and displacement. More axial yarns assembled at the impact side resulted in greater force oscillation, decreased heat generation in small-angle braided tubes, and reduced fiber tows fracture, delamination, and in-plane shear cracks in the wall of large-angle braided tubes.