Understanding the influence of laminate stacking sequence on strain/stress concentrations in thin laminates at repair holes with large scarf angles

Mahdi Damghani, Jerzy Bakunowicz, Adrian Murphy

Research output: Contribution to journalArticle

1 Citation (Scopus)
110 Downloads (Pure)

Abstract

Scarf repair is widely used in the restoration of structural performance of damaged aircraft secondary structures. Such repairs result in reduced thickness sections which are significantly larger than those associated with typical fastener holes. Significant literature exists on the distribution of strain/stress concentration in fastener hole geometries, both straight sided and countersunk, but is lacking for the geometries associated with shallow scarf angles and thin laminates. Hence, herein three-dimensional finite element models are developed to understand the influence of stacking sequence and scarf angle on strain/stress concentrations. The results demonstrate and quantify for the first time that strain concentrations are not only dependant on the laminate membrane stiffness but also on laminate bending stiffness, due to the anisotropy created as a result of scarfing angle, hole geometry and laminate thickness. Scarfing is demonstrated, for typical repair geometry associated with foreign object damage (hole diameter 20 mm, scarf angles 3 to 7 degrees), to elevate strains by up to 2.5 times when compared to equivalent diameter straight-sided holes in laminates of thickness ~1 mm.
Original languageEnglish
Number of pages12
JournalJournal of Composite Materials
Early online date18 Jun 2019
DOIs
Publication statusEarly online date - 18 Jun 2019

Keywords

  • Scarf repair
  • scarf holes
  • scarf angle
  • stacking sequence
  • strain concentrations
  • stress concentrations
  • composite laminate

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