Damage detection in repairs using frequency response techniques

Structural health monitoring (SHM) technology may be applied to composite bonded repairs to enable the continuous through-life assessment of the repair's efficacy. Adhesively bonded joints are an ideal starting point for real-time, in situ monitoring due to known mechanisms and locations of failure. Similarly, the ability to accurately monitor the health of a joint has potential to aid acceptance of adhesive bonding. This paper describes the development of an SHM technique for the detection of debonding in composite bonded patches based on frequency response. Two commonly used repair schemes, the external doubler repair and the scarf repair, are examined. The paper outlines an experimental investigation on the frequency response of the repairs with and without defects under different boundary conditions. It was found that damage could be readily detected through changes in frequency response for both types of repair. The results are discussed with implications for the development of a technology to monitor the integrity of composite bonded repairs.