陶瓷颗粒增强环氧树脂复合涂层的力学性能及断裂机理分析

Study on mechanical property and fracture mechanism of ceramic particle-reinforced epoxy composite coating

采用不同含量的Al2O3、ZrO2、SiC、WC这4种陶瓷颗粒分别制备了陶瓷颗粒增强环氧树脂涂层（陶瓷／环氧复合涂层），测试了所制涂层的洛氏硬度与结合强度。通过场发射扫描电子显微镜（FESEM）观察拉伸试验后涂层断裂面的形貌，探讨了涂层的断裂失效方式和断裂机理。结果表明，4种陶瓷／环氧复合涂层的洛氏硬度均较纯环氧涂层高，达到77～107HR，呈现WC涂层〉Al2O3涂层〉ZrO2涂层〉SiC涂层的趋势。除了陶瓷颗粒本身的硬度，其与环氧树脂的相容性对涂层洛氏硬度的影响很大。适当的陶瓷颗粒加入量能提高涂层的结合强度，加入过多反而使结合力下降。涂层的气泡或孔隙等薄弱部位作为断裂源，在外应力的作用下形成宏观裂纹，裂纹沿着薄弱区域扩展并发生偏转，最终导致涂层的断裂脱落。

Ceramic particle-reinforced epoxy composite coatings （i.e. ceramic/epoxy composite coatings） were prepared using different contents of ceramic particles such as A1203, ZrO2, SiC, and WC, respectively. Their Rockwell hardness and bond strength were studied. The fracture plane morphologies of the coatings after tensile test were observed by field-emission scanning electron microscope （FESEM）. The fracture failure mode and mechanism were discussed. The results indicated that all the ceramic/epoxy composite coating have a higher Rockwell hardness than a pure epoxy coating, reaching 77-107 HR, and there is a trend of WC coating 〉 Al2O3 coating 〉 ZrO2 coating 〉 SiC coating. The Rockwell hardness of the coatings is greatly affected by the compatibility between ceramic particles and epoxy resin besides their own hardness. The bond strength of coating can be improved by proper addition of ceramic particles but decreased with excessive content of ceramic particles. Under the action of external stress, macro cracks are formed from the weak positions such as pores or micro-cracks in the coating acting as fractal sources, and then expand among weak areas and deflect, leading to the eventual fracture and fall-off of the coating.