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Bondline Integrity Monitoring of Adhesively Bonded Structures via an Electromechanical Impedance Based Approach

Y. ZHUANG, F. KOPSAFTOPOULOS, F.-K. CHANG

Abstract


Bondline integrity is still one of the most critical concerns in the design of aircraft structures up to date. Due to the lack of confidence on the integrity of adhesive bondlines both during fabrication and service, the industry standards and regulations require assembling the composites using the inefficient “black-aluminum” approach, i.e. drill holes and use fasteners. Furthermore, current state-of-the-art nondestructive evaluation (NDE) and structural health monitoring (SHM) techniques are incapable of offering mature solutions on the issue of bondline integrity monitoring. Therefore, the objective of this work is to investigate the feasibility of embedding piezoelectric sensors into adhesively bonded joints to detect bondline integrity degradation. The proposed method employs an electromechanical-impedance (EMI) based diagnostic approach. This approach is based on the use of (i) micro-sensors embedded inside the adhesive leaving a minimal footprint on the material, (ii) numerical modeling of the EMI spectrum of the adhesive bondline, (iii) EMI based diagnostic algorithms for monitoring the bondline integrity, and (iv) the experimental assessment via adhesively bonded lap joints in static (varying loads) environment. The obtained results demonstrate the potential of the approach in providing increased confidence on the use of bonded joints for aerospace structures.

doi: 10.12783/SHM2015/26


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