胶接补强的含裂纹平板断裂特性的研究

Fracture Behavior of Adhesively Repaired Cracked Plate

为了提高含裂纹构件的承载能力,减少灾难性破坏事故的发生,近年来Jones等用胶粘剂将纤维增强复合材料胶接在构件中的裂纹部位,对飞机结构进行了成功的止裂。由于问题的复杂性,这类局部补强结构的应力强度因子,至今仍无解析解。作者用金属补钉代替纤维增强复合材料,用电测法研究了中心穿透裂纹试样补强后的应变场。试验表明:局部区域用补钉胶接后,平板中的裂纹扩展仍具有原有穿透裂纹的性质。由此,作者提出了等效应力强度因子,并根据实测的应变值,计算了等效应力强度因子。结果指出胶接金属补钉后,裂纹尖端处的应力强度因子可大幅度地降低;其承载能力较补强前提高50～90％。

Crack initiates and propagates in metallic aircraft structure. When one of these cracks reaches the critical size, catastrophic failure results. The advent of composites and high performance adhesives has led to much experimentation on repairing cracked metals with composite patches. But actual repairing of aircraft structure with composite patch has been, to the authors' best knowledge, only done by Jones[1]. Jones' method's shortcoming appears to be that it is expensive and requires too much labor. The authors believe that the contribution of the present paper is the overcoming of Jones' methods' shortcoming. The authors' experiments, using metal bonded patch, show that this shortcoming can be successfully overcome. As with Jones 'method, the authors' method makes patched metal plate more ductile than unpatched plate; furthermore, the authors' method increases the loadcarrying capacity of patched plate by 50—90%(the same or a little higher that of Jones' method[12]) as compared with that of unpatched plate. Thus, catastrophic failure can be delayed by the method of patching. Of course the actual application of the authors' method to repairing of aircraft structure cracks remains to be done. The authors employ strain gauges to determine the equivalent stress intensity factor instead of determining it with photoelasticity or finite element method. The authors believe that employing strain gauge is more convenient.