Long-term fracture toughness of wood

Mikael Fonselius

Research output: Book/ReportReport

3 Citations (Scopus)


Long-term fracture toughness of spruce, pine and Kerto LVL material has experimentally been determined. In mode II loading (forward shearing mode) an end-cracked beam specimen was used, while the compact tension specimen was used in mode I loading (opening mode). The specimens were exposed to a constant load, while the relative humidity was cyclically changed between 40 and 90 %. The length of a whole cycle was two weeks. In mode II loading the cyclical humidity conditions reduced the time to failure drastically in contrast to constant humidity conditions. For an end-cracked spruce beam loaded to 75 % of its short-term capacity the life time was reduced from 66 to 4 days. The duration of load effect is similar for pine material under cyclic humidity conditions. For Kerto LVL material the effect is more severe. In mode I loading no general conclusions could be drawn, as so few specimens were broken during the loading time of seven months.
Original languageEnglish
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Number of pages62
ISBN (Print)951-38-3918-4
Publication statusPublished - 1991
MoE publication typeD4 Published development or research report or study

Publication series

SeriesValtion teknillinen tutkimuskeskus. Tutkimuksia - Research Reports


  • timber
  • constructional timber
  • spruce
  • pine
  • Kerto LVL
  • fracture toughness
  • moisture content


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