Delamination migration in multidirectional composite laminates under mode I quasi-static and fatigue loading

Yu Gong*, Bing Zhang, Stephen Hallett

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

24 Citations (Scopus)
252 Downloads (Pure)

Abstract

Delamination migration is particularly critical in multi-directional composite laminates and is often observed in different loading scenarios and components. Further understanding on the migration mechanism, especially the similarities and differences in the quasi-static and fatigue delamination migrations, is important for the design of composite structures. In this study, the process of delamination migration under mode I quasi-static and fatigue loadings was experimentally investigated for specimens with a +θ/−θ centreline interface. Specimens, with a specially designed stacking sequence, which allows migration events using a simple Double Cantilever Beam set-up, were tested for θ = 75° and 60°. Delamination migration via intralaminar ply splitting has been observed and this was confirmed by the X-ray computed tomography scan results. All the specimens from both quasi-static and fatigue loadings had a fairly similar sequence of damage events; delamination grows through the −θ and +θ ply block successively until it reaches the 0° ply that prevents further migration. The delamination paths and shape of fracture surfaces were observed to be the same, while the Scanning Electron Microscope fractography results showed that the quasi-static fracture surface was rougher in comparison with that of fatigued specimens. In addition, the distances of migration points from the pre-crack tip were slightly smaller in the fatigue specimens, which may indicate a greater propensity for migration under fatigue loading. This study provides important guidelines to the damage tolerance design of multidirectional composite structures and the verification of advanced numerical modelling technologies.

Original languageEnglish
Pages (from-to)160-176
Number of pages17
JournalComposite Structures
Volume189
Early online date31 Jan 2018
DOIs
Publication statusPublished - 1 Apr 2018

Keywords

  • Carbon fibre
  • Delamination
  • Transverse cracking
  • Mechanical testing

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