结构诱导纤维屈曲对NCF复合材料性能与损伤演化的影响

Effects of structure-induced fiber buckling on the mechanical performance and damage evolution of NCF composites

  • 摘要: 为揭示编织结构对多轴向无屈曲织物(NCF)复合材料力学性能的影响机制,本文提出了一种以面内波纹比为统一表征参数的NCF结构描述与仿真建模方法,将编织结构参数对纤维几何形态的影响等效为纤维的面内波纹,实现对NCF复合材料结构与性能的统一描述与预测,并系统分析了编织结构对其拉伸、压缩及损伤演化行为的影响。基于Micro-CT表征获得的三种NCF织物的结构参数,建立了考虑纤维束截面变化的高保真建模方法,构建了面内波纹比分别为0.032、0.037、0.042的NCF复合材料模型,并结合三维Hashin失效准则,对其拉伸与压缩力学响应进行了数值模拟。结果表明,拉伸和压缩强度预测误差均小于8%,与实验结果吻合良好,同时裂纹路径与实验测试断裂形貌具有较好的一致性,验证了所提出结构描述及仿真建模框架的有效性。参数敏感性表明,随着波纹比的增大,复合材料的拉压强度均呈明显下降趋势,其中压缩性能对波纹更敏感。进一步的损伤演化分析揭示,面内波纹比的增大会促使材料内部损伤由分散扩展向局部失稳转变,裂纹更易在波纹几何缺陷处萌生并提前扩展,加速宏观承载能力退化。本文从几何等效表征、细观建模与定量损伤机理层面,为多轴向无屈曲织物复合材料的结构设计与性能优化提供了新的分析思路。

     

    Abstract: In order to reveal the influence mechanism of braided structure on the mechanical properties of multi-axial non-buckling fabric (NCF) composites, this paper proposes a NCF structure description and simulation modeling method with in-plane ripple ratio as a unified characterization parameter. The influence of braided structure parameters on the geometric morphology of fibers is equivalent to the in-plane ripple of fibers, which realizes the unified description and prediction of the structure and properties of NCF composites, and systematically analyzes the influence of braided structure on its tensile, compressive and damage evolution behavior. Based on the structural parameters of three kinds of NCF fabrics obtained by Micro-CT characterization, a high-fidelity modeling method considering the change of fiber bundle cross-section was established, and NCF composite models with in-plane ripple ratios of 0.032, 0.037 and 0.042 were constructed. Combined with the three-dimensional Hashin failure criterion, the tensile and compressive mechanical responses were numerically simulated. The results show that the prediction errors of tensile and compressive strength are less than 8 %, which are in good agreement with the experimental results. At the same time, the crack path is in good agreement with the fracture morphology of the experimental test, which verifies the effectiveness of the proposed structural description and simulation modeling framework. The parameter sensitivity shows that with the increase of the corrugation ratio, the tensile and compressive strength of the composites show a significant downward trend, and the compression performance is more sensitive to the corrugation. Further damage evolution analysis reveals that the increase of the in-plane waviness ratio will promote the transformation of the internal damage of the material from dispersed expansion to local instability, and the cracks are more likely to initiate and propagate in advance at the geometric defects of the waviness, accelerating the degradation of the macroscopic bearing capacity. This paper provides a new analysis idea for the structural design and performance optimization of multi-axial non-buckling fabric composites from the aspects of geometric equivalent characterization, mesoscopic modeling and quantitative damage mechanism.

     

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