Journal Published Online: 27 June 2013
Volume 2, Issue 1

Crack Propagation Fracture Toughness of Several Wood Species

CODEN: ACEMF9

Abstract

In materials with process zones, such as fiber-bridging zones in wood, it is crucial to characterize fracture toughness as a function of crack growth, known as the material's R curve. Here, a new fracture testing protocol developed to measure continuous R curves was used on six different species of solid wood—Douglas fir, Ponderosa pine, cedar, hemlock, balsa, and oak. Importantly, the new method uses monotonic loading, because unloading phases, as used in prior R curve methods, might damage the bridging fibers and alter subsequent toughness results. The crack length was recorded by a synchronized, automated imaging system. The solid wood R curves were measured for cracks running parallel to the wood grain direction with the crack plane normal to the radial direction (RL cracks) or normal to the tangential direction (TL cracks). The R curves for all species rose as a consequence of fiber bridging. TL toughness rose faster then RL toughness and therefore for long cracks TL toughness was higher for all species except cedar. The toughness trended upward as the density increased. Density had a much larger effect on fiber-bridging effects (i.e., the rise of the R curve) than it did on initiation toughness (i.e., the start of the R curve).

Author Information

Wilson, Elijah
Wood Science & Engineering, Oregon State Univ., Corvallis, OR, US
Mohammadi, Meisam
Wood Science & Engineering, Oregon State Univ., Corvallis, OR, US
Nairn, John
Wood Science & Engineering, Oregon State Univ., Corvallis, OR, US
Pages: 12
Price: $25.00
Related
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Stock #: ACEM20120045
ISSN: 2165-3984
DOI: 10.1520/ACEM20120045