Application of Acoustic Emission to Study Debond Growth in Co-cured/Co-bonded Composite Structures under Fatigue Loading

Sanjeev Kumar, S and Ramanaiah, B and Sudheendra, HN and Kamath, GM and Subba Rao, M (2006) Application of Acoustic Emission to Study Debond Growth in Co-cured/Co-bonded Composite Structures under Fatigue Loading. In: Proceedings of the 14th National Seminar on Aerospace Structures: Fatigue, Fracture and Ageing Structures, 30-31 Jan 2006, Nagpur, India.

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Increasing use of fibre-reinforced composite materials for primary and secondary components in aircraft construction has resulted in the development of lightweight and efficient structures. The major emphasis is now towards realization of such structures at reduced cost. In order to achieve this, newer concepts in design and manufacturing of structural composites are being explored. One such concept is to make components with integral construction through co-curing and co-bonding. Through this approach, one can integrate a number of sub-components to realize assemblies in a single cure. Adhesive bonding is one of the most widely used processes for joining two structural members. Adhesive bonding is preferred to mechanical fastening in view of the better structural stiffness that can be achieved. However, the quality of bonding depends on a number of parameters and is very sensitive to the quality of the bonding surfaces. In view of this, it may be extremely difficult and impractical to expect the same degree of bond quality over the bonded region, especially with large aircraft structural components. Hence, we invariably end up with variations in the bond quality. There is a concern from the designers as well as the certifying agencies with regard to these bond quality variations on its long-tem structural performance. With this background, Advanced Composites Division, NAL, has projected a test programme to understand how the structure with inherent good bonds, poor bonds and debonds would behave and to what extent the presence of defects would reflect on the structural integrity. It is essential that the growth of debonds, debond initiation at poorly bonded regions are monitored in real-time to assess the structural integrity. Among the conventional Non-destructive Evaluation (NDE) techniques, Acoustic Emission (AE) is probably the only technique that would provide this information. In this paper, we describe the application of AE technique to monitor defect initiation and growth of debonds during fatigue cycling in co-cured/co-bonded structural components such as flaps for a civilian aircraft. This provides useful information towards establishing damage tolerance of a co-cured/co-bonded composite structure.

Item Type: Conference or Workshop Item (Paper)
Uncontrolled Keywords: Bonded composite joints;Debonds;Non-destructive evaluation (NDE);Acoustic emission (AE);Structural integrity;Fatigue cycling
Subjects: CHEMISTRY AND MATERIALS > Composite Materials
Depositing User: Ms. Alphones Mary
Date Deposited: 25 Nov 2010 08:00
Last Modified: 25 Nov 2010 08:44

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