三维四向编织CMCs拉伸性能及损伤演化数值预测

发展了一种能够预测三维四向编织陶瓷基复合材料(3D-B-CMCs)拉伸模量与强度以及损伤演化过程的数值计算方法.首先,利用复合圆柱(CCA)和全局载荷分担(GLS)两种模型预测了纤维束的弹性模量和拉伸强度;然后,利用微焦点CT技术建立了能够反映3D-B-CMCs真实编织几何结构的胞元模型;其次,采用Hashin纤维束失效模型以及考虑单元尺寸的各向异性损伤力学本构模型,编制了ABAQUS/UMAT子程序,对3D-B-CMCs材料宏观拉伸的整个过程进行了计算模拟,预测了宏观拉伸应力-应变曲线,并与试验结果相吻合,证明了所建立方法的合理性和UMAT程序的有效性.同时,研究和讨论了拉伸过程中材料内部不同的损伤破坏模式对复合材料整体力学性能的影响,为材料的疲劳和蠕变等力学行为的内部损伤演化提供了依据.

Numerical prediction of tensile properties and damage evolution of three dimensional-four directional braided CMCs

A numerical method was developed to simulate the effective elastic properties, strength and progressive damage evolution of three dimensional-four braided ceramic matrix composites(3D-B-CMCs). Firstly, the elastic properties of yarns were predicted using the composite cylinder assemblage (CCA) model and the strength were predicted by the global load sharing (GLS) model considering the strength distribution of fibers. Then a three dimensional unit-cell finite element model was constructed based on the geometric data from micro-CT images. After that, anisotropic damage model has been adopted in the fiber tows with Hashin failure criteria and damage evolution law based on the characteristic length of element. The model was coded as the ABAQUS/UMAT subroutine program and implemented into monotonic tension simulation of 3D-B-CMCs. The stress-strain curve was predicted and correlated well with the experimental curve, which verified the rationality of the method and the validity of the UMAT subroutine program. At the same time, more insights of the influence of different damage process on material mechanical behavior were concluded from the simulation, which provide information for the progressive damage evolution of the material fatigue and creep.