Comparison of NMR and microwave NDE methods for defect detection in composite structures

Abstract

Abstract New advanced non-destructive evaluation (NDE) methods such as nuclear magnetic resonance (NMR) imaging and microwave NDE methods are being developed for their advantages and high resolution for defect detection in composite structures. Glass/epoxy composite structures are being used for many applications in industry. Often, glass/epoxy composite structures are used along with rubber lining in oil and gas pipe industry. Rubber is adhesively bonded to composite inner surface to meet the requirements. The interface of glass/epoxy composite and rubber lining is critical. Any de-bond (separation of adhesively bonded liner from composite surface) at the interface may lead to failure of composite structure due to corrosive gases and liquids. The present paper reports application of proton single sided NMR method to evaluate the de-bonds of rubber liner with composite. Results are compared with microwave NDE technique which is an advanced non-contact inspection method. Results indicate application of both these techniques for evaluation of bonded interfaces. Advantages of both the techniques over conventional techniques have been discussed. De-bonds within rubber lining were also detected and correlated.