Abstract Pore defects are unavoidable in 3D braided composites, and can highly reduce the mechanical performance. In this paper, multi-scale analyses are conducted to investigate the effects of pore defects on elastic constants for 3D five-directional braided composites. A modified Chamis model is proposed to calculate elastic properties of yarns with pore defects and validated by the finite element method (FEM). The representative volume cell (RVC) with pore defects is established to predict elastic constants of braided composites, and results are compared with those by experiments and full-scale conventional model. Also, how voids influence elastic properties of yarns and braided composites are fully discussed. Furthermore, the homogenized full-scale model is developed in order to evaluate the possibility and facility in macroscopic performance characterization of braded composites with void defects. Results show that the analytical model is efficient and accurate in elastic property calculation of yarns. It is proper to predict elastic performance of braided composites by RVC with voids. The conclusion indicates elastic properties of yarns and braided composites are significantly influenced by voids. The full-scale conventional modeling of braided composites with voids is extremely complex and time-consuming, which can be solved by the homogenization method to a great extent.

中文翻译：

---

考虑孔隙缺陷的 3D 五向编织复合材料多尺度弹性性能预测

摘要 孔隙缺陷在3D编织复合材料中是不可避免的，会大大降低力学性能。在本文中，进行了多尺度分析以研究孔隙缺陷对 3D 五向编织复合材料的弹性常数的影响。提出了一种改进的 Chamis 模型来计算具有孔隙缺陷的纱线的弹性性能，并通过有限元方法 (FEM) 进行验证。建立了具有孔隙缺陷的代表性体积单元（RVC）来预测编织复合材料的弹性常数，并将结果与​​实验和全尺寸常规模型的结果进行比较。此外，还充分讨论了空隙如何影响纱线和编织复合材料的弹性性能。此外，开发均质化的全尺寸模型是为了评估具有空隙缺陷的编织复合材料的宏观性能表征的可能性和便利性。结果表明，该解析模型在纱线弹性性能计算中是有效且准确的。用带空隙的 RVC 预测编织复合材料的弹性性能是合适的。结论表明纱线和编织复合材料的弹性性能受空隙的显着影响。带空隙的编织复合材料的全尺寸常规建模极其复杂和耗时，这在很大程度上可以通过均质化方法解决。用带空隙的 RVC 预测编织复合材料的弹性性能是合适的。结论表明纱线和编织复合材料的弹性性能受空隙的显着影响。带空隙的编织复合材料的全尺寸常规建模极其复杂和耗时，这在很大程度上可以通过均质化方法解决。用带空隙的 RVC 预测编织复合材料的弹性性能是合适的。结论表明纱线和编织复合材料的弹性性能受空隙的显着影响。带空隙的编织复合材料的全尺寸常规建模极其复杂和耗时，这在很大程度上可以通过均质化方法解决。