樹種による組織構造及び熱軟化特性の違いが木材の横引張変形特性へ及ぼす影響

Abstract

To obtain the information about maximum possible tensile deformation of wood, deformation properties of various wood species in lateral tension were studied. In addition, we observed fracture sections of lateral tensile tests in water, in order to examine the effect of anatomy on the deformation properties. Tensile deformation properties were measured in water at 25℃ or 80℃. The test specimens have different angles of the tensile direction to the annual rings (0°, 45°, 90°). The results obtained were as follows. 1) Failure strain of the hardwood specimens were not larger than the specimens of Hinoki at 80℃ in water. 2) At the specimen of angle 45°, failure strain increased proportionally with the decrease in density. 3) In all of specimens, failure strain in water saturated condition were larger at 80℃ than 25℃. However, failure strain were not increased proportionally with the decrease in elastic modulus. This result suggests that softening of wood with moisture and temperature course not only capability for the deformation of cell shapes but also origin of the fracture. 4) Result of observation of the fracture sections of lateral tensile tests, specimen of Keyaki having large pores susceptible to fracture along the sequence of large pores. These results suggest that lateral tensile deformation properties were greatly affected by anatomy. Therefore, in order to increase the tensile deformation it is necessary to deform of cell shapes which affected by density, thermal-softening caused by glass transition of lignin and anatomy, i.e, ray tissue or large pores.