Reducing-yarn technique and flexural properties of 3D braided composites with tapered cross-section
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摘要: 探讨了变截面三维编织预制件减纱净成型原理, 结合图像观测与拓扑分析方法表征减纱区域细观结构, 对比减纱变截面与切削变截面复合材料截面缩减区域及相应等截面复合材料的弯曲力学性能, 并分析两种变截面试件在破坏模式上的异同。结果表明: 减纱应遵循的原则是保证具有连续可编织性, 减纱预制件在截面缩减区域呈现平滑的梯形过渡, 其弯曲模量与强度显著高于切削变截面试件而略低于等截面试件, 且表现为以纱线断裂为主、包括基体开裂和纤维抽拔等模式的复合型破坏。
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关键词:
- 变截面三维编织复合材料 /
- 减纱工艺 /
- 细观结构 /
- 弯曲性能 /
- 破坏模式
Abstract: Mechanisms of near-net-shape reducing-yarn braiding were discussed. Microstructures in yarn-reducing regions were characterized by image observation and topological analysis. Flexural properties in the tapered regions of the reducing-yarn composites or cut composites and those of the uniform composites were compared. Finally, failure mechanisms of the reducing-yarn composites and cut composites were analyzed. The results indicate that continuity of the braiding process after yarn reduction must be ensured. The reducing-yarn preforms have a trapezoid profile near the reducing-yarn cross-section. Flexural properties of the reducing-yarn composites are higher than those of cut counterparts but lower than the uniform composites. The reducing-yarn composites show compound failure modes, which are dominated by yarn breakage and also include matrix cracking and fiber pulling-out. -
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