Molecular dynamics investigation on the interfacial shear creep between carbon fiber and epoxy matrix
Molecular dynamics investigation on the interfacial shear creep between carbon fiber and epoxy matrix
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DOI：
10.1016/j.apsusc.2020.148013
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发表时间：
2021-01-30
影响因子：
6.7
通讯作者：
Wu, Chao
中科院分区：
文献类型：
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作者：
Tam, Lik-ho;Jiang, Jinqiao;Wu, Chao
碳纤维增强聚合物（CFRP）复合材料在使用过程中会受到外载荷的作用，纤维与基体之间会发生界面蠕变，最终导致界面滑移。CFRP复合材料由于界面蠕变而丧失界面完整性，长期耐久性减弱。为了了解退化，蠕变过程中界面结构变化的微观细节是必不可少的。本研究旨在利用分子动力学模拟研究碳纤维/环氧树脂界面在不同剪切载荷水平下的微观蠕变行为。构建了一个由环氧树脂分子与代表纤维外层的石墨片键合组成的分子界面模型，并通过将键合环氧树脂的质量密度、玻璃化转变温度和杨氏模量与实验测量值进行比较来验证该模型。根据蠕变模拟，存在蠕变失效开始的阈值应力，高于该阈值应力，界面分离。相比之下，没有界面脱离下发生的低应力制度，其中的位移-力曲线被绘制和用于量化的能量障碍的蠕变失效的发作。同时，将界面的应变和应力演化与界面结构变化相关联，以了解界面蠕变机制。该研究为纤维/基体体系界面蠕变行为的分子机理研究提供了理论依据，并为界面蠕变行为的多尺度研究框架奠定了基础。
Carbon fiber-reinforced polymer (CFRP) composite is subject to external loads during service life, suffering the interfacial creep between the fiber and the matrix and eventually the interfacial slippage. CFRP composite loses the interfacial integrity due to the interfacial creep and the long-term durability is weakened. In order to understand the degradation, microscopic details of interfacial structural changes during the creep are essential. This study aims to investigate microscopic creep behavior of a carbon fiber/epoxy interface at different shear load levels using molecular dynamics simulations. A molecular interface model consisting of an epoxy molecule bonded to graphite sheets representing the fiber outer layer is constructed, which is validated by comparing the mass density, glass-transition temperature and Young's modulus of bonded epoxy with experimental measurements. According to the creep simulation, there is a threshold stress for the onset of creep failure, above which the interface detaches. Comparatively, no interfacial detachment occurs under the low stress regime, where the displacement-force curve is plotted and used to quantify the energy barrier to the onset of creep failure. Meanwhile, the strain and stress evolution of the interface are correlated to interfacial structural changes to understand the interfacial creep mechanism. This study provides molecular insights into the interfacial creep behavior in the fiber/matrix system and form the basis of multiscale investigation framework on the interfacial creep behavior.