Piezoelectric monitoring of the reliability of adhesive joints

Since the reliability of adhesively bonded joints for composite structures is dependent on many parameters such as the shape and dimensions of joints, type of applied load, and environment, so an accurate estimation of the fatigue life of adhesively bonded joints is seldom possible, which necessitates an in-situ reliability monitoring of the joints during the operation of structures. In this study, a self-sensor method for adhesively bonded joints was devised, in which the adhesive used works as a piezoelectric material to send changing signals depending on the integrity of the joint. In order to validate the method, the piezoelectric properties of the adhesive were measured during the fatigue test. Electrically conducting adherends were used as electrodes without embedded sensors, and the adhesively bonded joint was modeled as the equivalent parallel circuit composed of electric charge and capacitance. From the investigation, it was found that the electric charge increased gradually as cracks initiated and propagated in the adhesive layer, and had its maximum value when the adhesively bonded joint failed. So it is feasible to monitor the integrity of the joint during its lifetime. Finally, a relationship between the piezoelectric property of the adhesive and crack propagation was obtained from the experimental results.

[1]  Pietro Salvini,et al.  A PROCEDURE FOR FATIGUE LIFE PREDICTION OF SPOT WELDED JOINTS , 1997 .

[2]  D. A. Dillard,et al.  Nondestructive evaluation of model adhesive joints by PVDF piezoelectric film sensors , 1993 .

[3]  Daniel J. Inman,et al.  Self-Monitoring and Self-Healing Jointed Structures , 2001 .

[4]  C. Bert,et al.  The behavior of structures composed of composite materials , 1986 .

[5]  Dai Gil Lee,et al.  Development of a Failure Model for the Adhesively Bonded Tubular Single Lap Joint , 1992 .

[6]  D. A. Dillard,et al.  Embedded piezoelectric sensors to measure peel stresses in adhesive joints , 1994 .

[7]  Victor Giurgiutiu,et al.  Experimental Investigation of E/M Impedance Health Monitoring for Spot-Welded Structural Joints , 1999 .

[8]  Robert D. Adams,et al.  Stress Analysis of Adhesive Bonded Tubular Lap Joints , 1977 .

[9]  Y. Im,et al.  An Experimental Study of Fatigue Strength for Adhesively Bonded Tubular Single Lap Joints , 1991 .

[10]  Dai Gil Lee,et al.  The effects of surface roughness and bond thickness on the fatigue life of adhesively bonded tubular single lap joints , 2000 .

[11]  D. Lee,et al.  Torque Transmission Capabilities of Bonded Polygonal Lap Joints for Carbon Fiber Epoxy Composites , 1995 .

[12]  J. Vinson,et al.  Joining of Composite Material Structures , 1987 .

[13]  D. Lee,et al.  Hygrothermal effects on the strength of adhesively bonded joints , 1998 .

[14]  D. Lee,et al.  Development of a Fatigue Failure Model for the Adhesively Bonded Tubular Single Lap Joint under Dynamic Torsional Loading , 1996 .

[15]  D. Lee,et al.  Analysis of the Tubular Single Lap Joint with Nonlinear Adhesive Properties , 1995 .

[16]  Dai Gil Lee,et al.  An Experimental Study of the Static Torque Capacity of the Adhesively-Bonded Tubular Single Lap Joint , 1996 .

[17]  Antonio Arnau,et al.  Fundamentals on Piezoelectricity , 2004 .