Mechanical properties and damage mechanisms of closed circular preforms and overlapped stitched composite tubes under lateral compression, impact, and hydrostatic pressure were studied. The functional failure pressures of the tubes with different boundary conditions were determined and compared. Stitch at the overlapped zone creates stress risers that lead to premature functional failure at a hydrostatic pressure at ∼1/3 of the theoretical maximum pressure of the tube as delamination occurs at the overlapping region. Seamless tubes reached values close to theoretical operating hydrostatic pressures before leakage was observed at the tube ends. The deflection of the overlapped stitched tube due to lateral compression is less than the deflection in the seamless tube, and it is limited to 5% of the inner diameter using the Spangler equation. Brittle kinks, cracks, and delamination occur in overlapped stitched tubes while seamless tubes regain the shape with limited localized cracks after unloading. The fabric architecture of a seamless tube allows for the reorientation of fiber tows as cracks develop in the matrix, thus resulting in a lesser extent of damage when the tube is subject to impact.

中文翻译：

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无缝和重叠缝合复合管在静水压力、侧向压缩和冲击下力学性能的实验研究

研究了封闭圆形预制件和重叠缝合复合管在横向压缩、冲击和静水压力下的力学性能和损伤机制。确定并比较了具有不同边界条件的管子的功能失效压力。重叠区域的缝合会产生应力上升，当重叠区域发生分层时，在管子理论最大压力的 1/3 左右的静水压力下，会导致过早的功能失效。在管端观察到泄漏之前，无缝管达到了接近理论工作静水压力的值。由于横向压缩，重叠缝合管的挠度小于无缝管中的挠度，并且使用 Spangler 方程将其限制为内径的 5%。重叠缝合管会出现脆性扭结、裂纹和分层，而无缝管在卸载后恢复形状，局部裂纹有限。无缝管的织物结构允许纤维束在基体中出现裂纹时重新定向，从而在管受到冲击时减少损坏程度。