Heat treated wood and the influence on the impact bending strength

A.J.M. Leijten
Delft University of Technology, Delft, The Netherlands

As part of a national research program for the development of a timber guardrail tests have been conducted to gain knowledge about the impact strength of timber. Tests were carried out on Angelim Vermelho, Douglas Fir, Ash and Larch and three temperature treated wood species, Douglas Fir, Spruce and Pine. Three point impact bending tests were performed with a loading speed of 7m/s. A high-speed camera was used to determine the time of failure. Computer simulations were used to determine the bending moment at the time of failure as literature showed other methods to be inadequate or questionable. Peculiar impulse transmitting effects were detected by the high-speed camera (9000 images/s).  It was concluded that the impact strength is wood species and grade dependent. Some wood species did not show any significant bending strength reduction for others the strength reduction was dramatic.

Key words: Guardrail, timber, impact, crash barrier, wood species, strength