Chapter 2 Flashcards
dimensional and volumetric changes:
- shrinkage anisotropy
- shrinkage
- swelling
WHY TO KNOW ABOUT ANISOTROPY
✓ FOR DETERMINING PROPERTIES OF VARIOUS DIRECTION
✓ WISE UTILIZATION OF WOOD
THE WOOD HAS DIFFERENT PROPERTIES DEPENDING ON ITS
THREE GRAIN DIRECTIONS OR SECTIONS WHICH ARE THE:
a. tangential directions
b. radial directions
c. longitudinal directions
- Bound water is removed
from the cell wall - Reduction in wood
dimension and volume as it
losses moisture below FSP
expressed in percent.
shrinkage
WOOD SHRINKAGE OCCURES IN:
a. Radial Shrinkage
b. Tangential Shrinkage
c. Longitudinal Shrinkage
- is the amount the wood moves perpendicular to the growth rings or along the radial or medullary rays that transport nutrients into the interior of the tree.
- this is a small amount of movement but still should be accounted for.
Radial shrinkage
- is the amount the wood moves along the growth rings.
Tangential shrinkage
REASONS FOR HIGHER TANGENTIAL SHRINKAGE:
➢ THE RESTRICTING EFFECT OF THE RAY ON THE RADIAL PLANE
➢ CELL WALL ON THE TANGENTIAL DIRECTION IS THICKER (IN DIRECTION) THAN RADIAL
➢ THE INCREASED THICKNESS OF THE MIDDLE LAMELLA IN TANGENTIAL WALL COMPARED TO THE RADIAL WALL.
➢ THE EARLY WOOD AND LATEWOOD RELATIONSHIP
➢ ORIENTATION OF MICROFIBRIL ANGLE (MFA)
- grain that is parallel, or tangent to the growth rings
Tangential Plane
- grain that is perpendicular to the growth rings
Radial Plane
- the amount a piece of wood will shrink lengthwise
Longitudinal Shrinkage
LONGITUDINAL SHRINKAGE, IS SO SMALL—TYPICALLY ABOUT ________, THAT IT IS USUALLY INCONSEQUENTIAL TO THE VOLUMETRIC SHRINKAGE.
0.1% TO 0.2%
- Increase in wood dimension and volume as it gains moisture below FSP expressed in percent.
swelling
Swelling continues until the cell wall become completely ______ with water.
saturated
