Computing the growth of naturally-occurring disbonds in adhesively-bonded patches to metallic structures. (February 2016)

• Record Type: Journal Article
• Authors: Hu, W.; Jones, R.; Kinloch, A.J.
• Is Part Of: Engineering fracture mechanics. Volume 152(2016)
• Page Start: 162
• Page End: 173
• Publication Date: 2016-02
• Subjects: Adhesives -- Fatigue crack growth -- NASGRO -- Joints -- Scatter; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2015.10.041
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: Previous studies of delamination growth have been limited to long artificial disbonds. This paper is the first to analyse the growth of naturally occurring disbonds. It shows how accurate results can be obtained using the NASGRO equation. The constants required can be derived from tests on specimens with large disbonds. This approach can be used ala FAA AC 120-107b to certify bonded structures. Abstract: In 2009 the US Federal Aviation Administration (FAA) introduced a slow growth approach for certifying composite and adhesively-bonded structures. This approach requires that delamination or disbond is slow, stable and predictable under cyclic-fatigue loads. The present paper addresses the challenge of developing a methodology capable of enabling this approach to certification to be implemented. To this end we have examined the growth of disbonds from small naturally-occurring material discontinuities in adhesively-bonded structures. It is shown that, for the examples studied, the disbond growth histories can be accurately computed using a form of the Hartman and Schijve variant of the NASGRO crack-growth equation. It is also shown that the scatter in the disbond growth histories can be captured by allowing for small changes in the fracture-mechanics threshold term. These findings suggest that the Hartman and Schijve variant of the NASGRO crack-growth equation has the potential to address the 'slow growth' approach to certifying composite/bonded structures and bonded repairs outlined in the US FAA Airworthiness Advisory Circular No: 20-107B.