Composite repairs to bridge steels demystified. (1st June 2017)

• Record Type: Journal Article
• Authors: Ali, K.; Singh Raman, R.K.; Zhao, X.L.; Jones, R.; McMillan, A.J.
• Is Part Of: Composite structures. Volume 169(2017)
• Page Start: 180
• Page End: 189
• Publication Date: 2017-06-01
• Subjects: Aging bridges -- Composite repairs -- Fatigue crack growth -- Fractals -- ASTM E647-13a; Composite construction -- Periodicals; Composites -- Périodiques; 624.18
• DOI: 10.1016/j.compstruct.2016.07.049
• Languages: English
• ISSNs: 0263-8223

Abstract

Abstract: This paper examines crack growth associated with carbon fibre reinforced plastic (CFRP) repairs to cracked bridge steels and boron epoxy composite and fibre metal patch repairs to cracked aluminium alloy structures. It is first shown that the da/dN versus ΔK curves associated with bridge steels is very similar to that seen in the high strength aerospace steel D6ac. The importance of 1st ply failure, which was first observed on a boron epoxy repair to the F-111 D6ac steel wing pivot fitting, and how to alleviate this failure mechanism is then discussed as is the common design approach whereby after patching the repair is designed to have a ΔK beneath the ASTM long crack threshold ΔKth . It is shown that crack growth in bridge steels repaired with CFRP patches and in aluminium alloy structures repaired with either boron epoxy or glare patches exhibit a near linear relationship between the log of the crack length and the number of cycles. We then show that crack growth in these repairs can be represented by the same simple master curve relationship that has been found to hold for cracks growing in both operational aircraft and full scale fatigue tests. These findings are important since they suggest that the methodology used by the Royal Australian Air Force to certify structural modifications to operational aircraft may also be applicable to composite repairs/modifications to steel bridges, which are generally experience significantly lower stresses.