[论文解读] Multiscale modeling of microscale fiber reinforced composites with nano-engineered interphases

S. I. Kundalwalal, S. Kumar+1 more|arXiv (Cornell University)|Sep 17, 2015

Composite Material Mechanics参考文献 56被引用 4

一句话总结

本研究开发了一种多尺度计算模型，用于研究在微米尺度纤维周围分散有定向碳纳米管（A-CNTs）的纤维增强复合材料中的应力传递行为。通过结合分子动力学模拟与微结构力学脱粘模型，并采用弹簧层界面模型，研究结果表明，A-CNTs的轴向排列显著增强了界面载荷传递能力，而界面弱化则降低了沿纤维方向的径向应力分布。

ABSTRACT

This study is focused on the mechanical properties and stress transfer behavior of multiscale composites containing nano- and micro-scale reinforcements. The distinctive feature of construction of this composite is such that the carbon nanostructures (CNS) are dispersed in the matrix around the continuous microscale fiber to modify microfiber-matrix interfacial adhesion. Such CNS are considered to be made of aligned CNTs (A-CNTs). Accordingly, multiscale models are developed for such hybrid composites. First, molecular dynamics simulations in conjunction with the Mori-Tanaka method are used to determine the effective elastic properties of nano-engineered interphase layer composed of CNS and epoxy. Subsequently, a micromechanical pull-out model for a continuous fiber multi-scale composite is developed, and stress transfer behavior is studied for different orientations of CNS considering their perfect and imperfect interfacial bonding conditions with the surrounding epoxy. Such interface condition was modeled using the linear spring layer model with a continuous traction but a displacement jump. The current pull-out model accounts for the radial as well as the axial deformations of different orthotropic constituent phases of the multiscale composite. The results from the developed pull-out model are compared with those of the finite element analyses and are found to be in good agreement. Our results reveal that the stress transfer characteristics of the multiscale composite are significantly improved by controlling the CNT morphology around the fiber, particularly, when they are aligned along the axial direction of the microscale fiber. The results also show that the CNS-epoxy interface weakening significantly influences the radial stress along the length of the microscale fiber.

研究动机与目标

• 研究由定向碳纳米管与环氧树脂组成的纳米工程化界面的多尺度复合材料的力学行为。
• 理解碳纳米管形貌及界面结合条件对混合微纳米增强复合材料中应力传递的影响。
• 开发一种考虑复合材料正交各向异性相中径向与轴向变形的微结构力学脱粘模型。
• 通过有限元分析验证所提出模型的准确性，以预测界面应力分布。

提出的方法

• 结合分子动力学模拟与Mori-Tanaka均质化方法，以确定CNT-环氧树脂界面相的有效弹性性能。
• 开发用于具有多尺度增强体的连续纤维复合材料的微结构力学脱粘模型。
• 采用线性弹簧层模型来表征界面行为，包含位移跳跃与连续应力传递。
• 在正交各向异性组成相（包括微纤维、CNTs与基体）中引入径向与轴向变形。
• 通过弹簧刚度参数建模CNT与环氧之间理想与非理想界面结合条件。
• 通过有限元模拟验证解析脱粘模型的准确性，以确保应力传递预测的可靠性。

实验结果

研究问题

• RQ1 CNTs在微纤维周围的取向如何影响多尺度复合材料中的界面应力传递？
• RQ2 CNTs与环氧之间界面结合质量对沿纤维方向的径向应力分布有何影响？
• RQ3 正交各向异性相中的径向与轴向变形如何影响整体载荷传递机制？
• RQ4 纳米工程化界面相在多大程度上提升了微米尺度纤维增强复合材料的力学性能？
• RQ5 所提出的解析脱粘模型在预测应力传递方面与有限元分析相比表现如何？

主要发现

• CNTs在微纤维周围沿轴向排列显著提高了复合材料中的应力传递效率。
• 纳米工程化界面相增强了界面载荷传递能力，尤其当CNTs沿纤维轴向排列时效果更显著。
• CNT-环氧界面越弱，沿纤维长度方向的径向应力显著降低。
• 所开发的微结构力学脱粘模型与有限元分析结果具有良好一致性。
• 该模型成功捕捉了多尺度复合材料正交各向异性相中径向与轴向变形的耦合行为。
• Mori-Tanaka方法能准确预测CNT-环氧界面层的有效弹性性能。