Adhesive bond-line degradation detection via a cross-correlation electromechanical impedance–based approach. (November 2016)

• Record Type: Journal Article
• Authors: Dugnani, Roberto; Zhuang, Yitao; Kopsaftopoulos, Fotis; Chang, Fu-Kuo
• Is Part Of: Structural health monitoring. Volume 15:Number 6(2016)
• Page Start: 650
• Page End: 667
• Publication Date: 2016-11
• Subjects: Transducer -- sensor -- structural health monitoring -- piezoelectric -- actuator -- lap-joint -- diagnostic -- prognostic -- impedance; Structural health monitoring -- Periodicals; Structural stability -- Periodicals; Strength of materials -- Periodicals; Nondestructive testing -- Periodicals; Constructions -- Stabilité -- Périodiques; Résistance des matériaux -- Périodiques; Contrôle non destructif -- Périodiques; Electronic journals; 624.17
• DOI: 10.1177/1475921716655498
• Languages: English
• ISSNs: 1475-9217

Abstract

This article describes how piezoelectric transducers embedded in the adhesive bond-line of lap-joints can be used to effectively monitor structural integrity. Various lap-joint coupons with embedded piezoelectric transducers were manufactured with and without artificial contamination at the bond-line and tested statically and cyclically. A novel scheme based on the electromechanical impedance response of the transducer was implemented to predict the failure of the tested lap-joint samples. The results from the mechanical testing indicated that monitoring the transducer's electromechanical impedance is an effective way of predicting the failure of the bond-line. Specifically for static tests, local damage to the bond-line was consistently detected at approximately 84% of the failure load for transducers located at the center of the bond-line, whereas for transducers embedded near the edge of the bond-line, the failure of the adhesive was detected at 60% of the failure load. Moreover, preliminary fatigue tests showed that significant changes in the electromechanical impedance signals were apparent starting at 60% of the life of the bond-line. In addition to the mechanical testing, the effectiveness of the proposed electromechanical impedance–based scheme was investigated by means of a three-dimensional finite element model corresponding to the specific coupon geometry tested and through a two-dimensional analytical solution.