Numerical Simulation of Failure of Composite Coatings due to Thermal and Hygroscopic Stresses
Numerical Simulation of Failure of Composite Coatings due to Thermal and Hygroscopic Stresses
复制标题
复合涂层因热应力和吸湿应力而失效的数值模拟
DOI：
10.3390/coatings9040243
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发表时间：
2019-04-01
期刊：
影响因子：
3.4
通讯作者：
Mai, Yiu-Wing
中科院分区：
文献类型：
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作者：
Zhou, Helezi;Liu, Hong-Yuan;Mai, Yiu-Wing
由于环氧涂层的热膨胀和湿膨胀比刚性基材高，这些涂层承受高的热应力和吸湿应力，导致涂层/基材界面裂纹生长。在此，参数进行了系统的研究，环氧涂层与填料，以了解其对涂层/基体界面剥离所造成的热应力和吸湿应力。开发了一个有限元模型（FEM），以确定一个指标J积分值（Ji），在与临界JC值解释所获得的界面分层实验结果进行比较。有限元模拟表明，位于涂层边缘的界面预裂纹比中心处严重。一旦由热冲击或吸湿引发分层，它将沿涂层/基材界面迅速沿着扩展。然而，通过向涂层中添加合适的微米/纳米填料，热应力和吸湿应力给出较低的Ji值，从而可以有效地控制分层裂纹的扩展。模拟结果表明，结合填料具有较低的杨氏模量，较低的热膨胀系数和吸湿系数，较小的软填料的尺寸，较大的尺寸的刚性填料，和适当的长径比的棒状填料的涂层，更有效地防止界面分层。因此，有用的指导方针，以改善设计的环氧树脂复合涂层对分层增长，可以得到不同的工程应用。
Due to the higher thermal and moisture expansions of epoxy coatings than the rigid substrate, these coatings suffer from high thermal and hygroscopic stresses, leading to coating/substrate interfacial crack growth. Herein, a parametric study was conducted systematically on epoxy coatings incorporated with fillers, in order to understand their effects on coating/substrate interface delamination caused by thermal and hygroscopic stresses. A finite element model (FEM) was developed to determine an indicator J-integral value (Ji), in comparison with a critical JC value to interpret the obtained interface delamination experimental results. FE simulations showed that interfacial pre-cracks located at coating edges were more serious than those at the centre. Once delamination was triggered by thermal shock or moisture absorption, it propagated rapidly along the coating/substrate interface. However, by adding suitable micro-/nano-fillers to the coating the thermal and hygroscopic stresses give lower Ji values, so that delamination crack growth can be effectively controlled. The simulation results demonstrate that the incorporation of fillers with lower Young’s modulus, lower thermal expansion and moisture absorption coefficients, smaller size for soft fillers, larger size for rigid fillers, and suitable aspect ratios for rod-shape fillers to the coatings, are more effective against interface delamination. Hence, useful guidelines for improving the design of epoxy composite coatings against delamination growth can be obtained for different engineering applications.