2D编织C/SiC孔边致密化结构多尺度混合模型与拉伸性能

Multiscale hybrid modeling and tensile properties of 2D braided C/SiC with hole-edge densification structures

针对一种开孔2D编织C/SiC复合材料在化学气相浸渗过程中出现的孔边致密化结构,提出了一种表征孔边致密化结构的建模方法。考虑孔隙的随机分布,建立了纤维束尺度代表体积元模型,实现了2D编织C/SiC复合材料等效弹性模量的计算。在此基础上,建立了具有孔边致密化结构的2D编织C/SiC复合材料宏-细观组合模型。基于3D hashin失效准则与修正的Von Mises失效准则,建立了2D编织C/SiC复合材料的渐进损伤模型,模拟了其单轴拉伸应力-应变行为。通过与实验数据的对比分析,验证了模型的有效性。计算不同孔隙率、致密带半径以及孔径的开孔2D编织C/SiC复合材料拉伸强度并分析其影响规律。计算结果表明:随着孔隙率的增大,材料刚度与拉伸强度不断减小,当孔隙率从5%上升到20%时,抗拉强度降低26.05%;随着致密带半径的增加,材料刚度下降越缓慢,失效强度越大,当致密带半径从0 mm增大到0.75 mm时,抗拉强度提高14.17%;随着孔径增大,孔边应力集中效应增强,孔边损伤程度加剧,材料损伤越快,当孔径从0.5 mm增大到2 mm时,抗拉强度降低35.01%。

A modelling method is proposed to characterise the densification structure of the hole edges of 2D braided C/SiC composites during Chemical Vapour Infiltration(CVI).A Representative Volumetric Element(RVE)model,taking into account the random distribution of holes,is developed to calculate the equivalent elastic modulus of 2D braided C/SiC composites.On this basis,a macro-meso hybrid model of 2D braided C/SiC composites with a densified structure of the hole edge is developed.Based on the 3D hashin failure criterion and the modified Von Mises failure criterion,the progressive damage model of the 2D braided C/SiC composite is developed,and its uniaxial tensile stress-strain behaviour is simulated.The validity of the model is verified by comparison and analysis with experimental data.The tensile strength of the open-hole 2D braided C/SiC composites is calculated for different porosities,radii of the dense zone and hole diameters,and the effects are analysed.The results show that with the increase of porosity,the material stiffness and tensile strength decreased,when the porosity increased from 5%to 20%,the tensile strength decreased by 26.05%;with the increase of radius of dense zone,the material stiffness decreased more slowly and the failure strength increased,when the radius of dense zone increased from 0 mm to 0.75 mm,the tensile strength increased by 14.17%;with the increase of hole diameter,the hole edge stress concentration effect is enhanced,the degree of damage to the hole edge increased,the faster the material damage,when the hole diameter increases from 0.5 mm to 2 mm,the tensile strength decreased by 35.01%.