A primary mechanism of adhesive bond failure is a degradation of the adherent/adhesive interfacial stiffness from unwanted contamination or exposure to those environmental factors, which reduce adhesion quality. Substantial research has been conducted on the assessment of adhesively bonded structures and the detection of “kissing” bonds. Advanced ultrasonic assessment methods to interrogate bonded joints and measure interfacial stiffness using a distributed spring interface model have been developed. Amplitude-based ultrasonic methods have traditionally been used in adhesive bond quality assessment, but recent advancements in ultrasonic phase measurements allow for high measurement resolution with low-uncertainty. In this work, an ultrasonic phase technique for the monitoring of adhesively-bonded interfaces is demonstrated. Constant frequency measurements are obtained from the ultrasonic phase of the reflection coefficient from the adhesive bond with a glass adherent, where the degree of cure is controlled by exposure to ultraviolet light. A peak in the phase of the reflection coefficient, as predicted by the interfacial spring model, is measured experimentally. It is shown that the peak phase predicts the interfacial stiffness when some frequency dependent threshold value is crossed. With knowledge of the acoustic impedances of both materials at the interface, the interfacial stiffness is determined by an inverse algorithm involving measurements of ultrasonic phase shifts of bonded joint reflections. By monitoring the interface of bonded structures and coatings, this method permits a nondestructive inspection of bond strength from structural construction through its service life.

粘合剂粘合失败的主要机制是粘合剂/粘合剂界面刚度因不希望的污染或暴露于那些降低粘合质量的环境因素而退化。已经对粘合结构的评估和“接吻”键的检测进行了大量研究。已经开发出先进的超声波评估方法来询问粘合接头并使用分布式弹簧界面模型测量界面刚度。传统上，基于振幅的超声波方法一直用于粘合剂粘合质量评估，但最近在超声波相位测量方面取得的进展允许具有低不确定性的高测量分辨率。在这项工作中，演示了一种用于监测粘合界面的超声波相位技术。恒定频率测量是从与玻璃粘合剂的粘合剂结合的反射系数的超声波相位获得的，其中固化程度通过暴露于紫外线来控制。正如界面弹簧模型所预测的，反射系数相位的峰值是通过实验测量的。结果表明，当超过某个频率相关阈值时，峰值相位可以预测界面刚度。了解两种材料在界面处的声阻抗后，界面刚度由一种逆算法确定，该算法涉及测量粘合接头反射的超声相移。通过监测粘合结构和涂层的界面，