ABSTRACT In order to evaluate the influence of void defects and interphase on the thermal expansion properties of three-dimensional woven carbon/carbon composites, a multi-scale numerical model was proposed to predict the effective thermal expansion coefficients considering void defects and interphase. On micro-scale, the effective thermal expansion coefficients of fiber bundles with void defects were predicted. On meso-scale, the effective thermal expansion coefficients of three-dimensional woven carbon/carbon composite with voids and interphase were predicted through a two-step homogenization procedure based on the asymptotic homogenization method and finite element method. The numerical model was validated by comparing with experimental measurements. Moreover, the influences of voids fraction and interphase modulus on the effective thermal expansion coefficients were examined quantitatively. The results indicate that the voids fraction has a negative impact on the coefficients of thermal expansion. The thermal expansion coefficients tend to decrease approximately linearly with the increase of voids fraction in fiber reinforcement and matrix, and decrease nonlinearly with the increase of voids fraction in interphase. The effective coefficients of thermal expansion increase as the increase of interphase elastic modulus, and the influence of interphase voids fraction on the coefficients of thermal expansion is becoming weaken as the increase of interphase elastic modulus. Graphical Abstract

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孔隙缺陷和界面对三维编织碳/碳复合材料热膨胀系数影响的数值评价

摘要 为了评估空隙缺陷和界面对三维编织碳/碳复合材料热膨胀性能的影响，提出了一种多尺度数值模型来预测考虑空隙缺陷和界面的有效热膨胀系数。在微观尺度上，预测了具有空隙缺陷的纤维束的有效热膨胀系数。在细观尺度上，通过基于渐近均质化方法和有限元方法的两步均质化程序，预测了具有空隙和界面的三维编织碳/碳复合材料的有效热膨胀系数。数值模型通过与实验测量的比较得到验证。而且，定量研究了空隙率和界面模量对有效热膨胀系数的影响。结果表明，空隙率对热膨胀系数有负面影响。热膨胀系数随着纤维增强体和基体中空隙率的增加呈近似线性下降趋势，随着界面层空隙率的增加呈非线性下降趋势。有效热膨胀系数随着相间弹性模量的增大而增大，相间空隙率对热膨胀系数的影响随着相间弹性模量的增大而减弱。图形概要 结果表明，空隙率对热膨胀系数有负面影响。热膨胀系数随着纤维增强体和基体中空隙率的增加呈近似线性下降趋势，随着界面层空隙率的增加呈非线性下降趋势。有效热膨胀系数随着相间弹性模量的增大而增大，相间空隙率对热膨胀系数的影响随着相间弹性模量的增大而减弱。图形概要 结果表明，空隙率对热膨胀系数有负面影响。热膨胀系数随着纤维增强体和基体中空隙率的增加呈近似线性下降趋势，随着界面层空隙率的增加呈非线性下降趋势。有效热膨胀系数随着相间弹性模量的增大而增大，相间空隙率对热膨胀系数的影响随着相间弹性模量的增大而减弱。图形概要 并随着界面中空隙率的增加而非线性减小。有效热膨胀系数随着相间弹性模量的增大而增大，相间空隙率对热膨胀系数的影响随着相间弹性模量的增大而减弱。图形概要 并随着界面中空隙率的增加而非线性减小。有效热膨胀系数随着相间弹性模量的增大而增大，相间空隙率对热膨胀系数的影响随着相间弹性模量的增大而减弱。图形概要