外加应变对航空有机涂层损伤规律的影响

Effect of prestrain on the degradation behaviour of aviation organic coatings

借助有机涂层预应变施加方法,跟踪观察户内加速试验过程中受到外加应变的航空有机涂层表面形貌变化,利用环境扫描电子显微镜进行显微组织表征,利用电化学阻抗谱进行特定频率的阻抗模值分析,进而综合研究航空有机涂层在外加应变和热带海洋大气环境耦合作用下的损伤规律和失效模型.研究发现,外加拉应变导致有机涂层的防护性能下降,外加拉应变水平越高,有机涂层损伤越严重,防护性能下降越多.进行户内加速试验过程中,受到外加拉应变的涂层防护性能进一步下降,外加拉应变越大,下降越快.受外加拉应变的涂层防护性能下降的原因是相应的应力水平超过有机涂层材料的断裂强度,从而在涂层内部形成微裂纹,构成外界溶液到达有机涂层/合金界面的通道.受到外加压应变后,有机涂层的防护性能不发生明显变化.进行户内加速试验过程中,受到外加压应变的涂层防护性能缓慢丧失,受到外加压应变水平越高,涂层防护性能下降越缓慢.

ABSTRACT The surface morphology of an aviation organic coating during indoor accelerated testing was continually observed by a prestrain method. Environmental scanning electron microscopy and electrochemical impedance spectroscopy were employed for micro-structural characterization and characteristic impedance modulus analysis to systematically study the degradation behavior and failure model of the organic coating under the co-effect of prestrain and tropical marine atmosphere. It is found that the protective properties of the organic coating show a dramatic decrease after tensile prestrain application and go further down during indoor accelerated testing;the degradation of the organic coating is positively correlated with the tensile prestrain level. It is thought that the loss of the protective properties is due to the relatively high stress level which exceeds the breaking strength of the organic coating materials, leading to the formation of microcracks, which serve as routes to the organic coating/alloy interface for solution. But the protective properties of the organic coating exhibit no change after compressive prestrain application and decrease slowly during indoor accelerated testing;the deg-radation of the organic coating is negatively correlated with the compressive prestrain level.