Abstract
Short term bending tests with end-notched beams at constant or
varying moisture content have shown an apparent contradictory
dependency between moisture content and strength. The higher the
moisture content the higher the strength. Varying moisture results
in particularly significant differences.In order to study this
phenomenon, moisture content and deformations perpendicular to
grain were monitored at a stepwise changing humidity (55%, 90% RH
at 20 degrees C). The normal stresses perpendicular to grain due
to restricted swelling were then obtained by assuming Hooke's law
applies and by neglecting deformation due to shear. Compression
stresses perpendicular to grain in excess of 6 MPa were found in
the vicinity of the notch following a period of adsorption.
Similarly, small tension stresses of the order 1 MPa were
registered in this area when the specimens were at their most dry
condition.It thus seems that the unexpected increase in strength
due to moisture uptake may in part be explained by the built-up of
compression stresses perpendicular to grain caused by the moisture
induced restricted swelling. Such compression stresses act as a
reinforcement which must first be overcome before a tension
perpendicular to grain failure can develop and ultimately lead to
failure.
Original language | English |
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Title of host publication | Proceedings of the 1996 International Conference on Wood Mechanics |
Place of Publication | Stuttgart |
Publisher | FMPA-Otto-Graf-Institut |
Publication date | 1996 |
Publication status | Published - 1996 |
Event | 1996 International Conference on Wood Mechanics - Stuttgart, Germany Duration: 14 May 1996 → 16 May 1996 |
Conference
Conference | 1996 International Conference on Wood Mechanics |
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Country/Territory | Germany |
City | Stuttgart |
Period | 14/05/1996 → 16/05/1996 |