Ageing of autoclaved epoxy/flax composites: effects on water absorption, porosity and flexural behaviour

Júlio Cesar dos Santos, Lívia Ávila de Oliveira, Túlio Hallak Panzera, Chrystel D L Remillat, Ian R Farrow, Vincent Placet, Fabrizio L Scarpa

Research output: Contribution to journalArticle (Academic Journal)

Abstract

This work investigates the effects of ageing on autoclaved composites made with unidirectional prepreg epoxy and flax tape in environments with 50% and 100% of relative humidity. A Design of Experiment (DoE) has been used first to determine the effect of the ageing time (0, 2, 4, 6, 8 and 16 days), type of bending (3-point and 4-point bending) and fibre orientation (longitudinal and transverse) on the water absorption and flexural properties of 50% saturated composites. A second experiment at 100% humidity has been also performed to further characterise the composites and to identify the equivalent ageing time that provides the mechanical behaviour of the 50% humidity samples after sixteen days. The water absorption and apparent porosity levels increase progressively with the ageing time, in particular for the case of transverse laminates; these features compromise the flexural properties of the composites. The laminates subjected to 4-point bending showed increased water absorption levels and improved flexural properties compared to the samples under 3-point bending. The flexural properties of flax composites at 50% humidity after 16 days are equivalent to those shown by composites immersed in water for less than one day.
Original languageEnglish
JournalComposites Part B: Engineering
Publication statusAccepted/In press - 20 Aug 2020

Keywords

  • flax composite
  • prepreg
  • ageing process
  • fibre orientation
  • flexural properties
  • water absorption
  • apparent porosity

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