Composite repairs to bridge steels demystified

K. Ali, R.K. Singh Raman , X.L. Zhao, R. Jones, A.J. McMillan

Research output: Contribution to journalArticleResearchpeer-review

11 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)180-189
Number of pages10
JournalComposite Structures
Volume169
DOIs
Publication statusPublished - 1 Jun 2017

Keywords

  • Aging bridges
  • ASTM E647-13a
  • Composite repairs
  • Fatigue crack growth
  • Fractals

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