Observations and impact of char layer formation and loss for engineered timber

Laura Schmidt*, Rory M. Hadden, Dilum Fernando

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The char layer plays a critical role in the fire behaviour of engineered timber. Several chemical and physical processes can reduce char layer thickness and integrity. A series of experiments studied 12 cross-laminated timber (CLT) columns (130 × 790 × 125 mm WxHxD) exposed to combined thermal (20 kW/m2 or 50 kW/m2) and mechanical loading (39 kN, eccentric). Char loss from the surface lamella was observed and the impact of this on the thermal response of the timber studied. In all cases, unprotected CLT exhibited fall-off of charred pieces. Cracking, shrinkage and movement of char contributed significantly to the exposure of underlying timber sections to external heating. There was no direct correlation between char fall-off and the measured glue line temperature in this configuration. To enable comparison between CLT with and without char fall-off, a thin layer of glass fibre-reinforced polymer was added to the exposed surface of six samples which prevented all char fall-off. Retention of the char layer significantly decreased temperatures beneath the char layer, loss of section and burning duration compared to samples with char fall-off.

Original languageEnglish
Article number104196
JournalFire Safety Journal
Volume147
Early online date4 Jun 2024
DOIs
Publication statusPublished - Jul 2024

Keywords / Materials (for Non-textual outputs)

  • Char fall-off
  • Char oxidation
  • Cross-laminated timber (CLT)
  • Debonding
  • Engineered timber
  • Fire dynamics
  • Fire safety
  • Heat transfer
  • Mass timber structure

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