Timber 1

Question 1

What are the three sub-systems of a tree?

Answer 1

Crown
Trunk
Root

Question 2

What is bark?

Answer 2

The outer layer of a tree
corklike and provides protection to the tree

Question 3

What is bast?

Answer 3

The inner bark which carries enriched sap from leave to cells

Question 4

What is cambium

Answer 4

Layer of living cells between the bast and the sapwood

Question 5

What is sapwood?

Answer 5

New growth carries raw sap up to the leaves- usually lighter in colour

Question 6

What is heartwood?

Answer 6

Mature timber that no longer carries sap- the heart of the tree providing the strength
usually darker in colour

Question 7

What are annual/growth rings?

Answer 7

Layers inside the tree which show age

Question 8

What trees do softwoods come from?

Answer 8

Evergreen coniferous trees

Question 9

What are the 6 types of grains?

Answer 9

Diagonal
Straight
Irregular
Spiral
Wavy
Interlocked

Question 10

What level of anisotropy does wood have?

Answer 10

90-95% of cells are elongated and vertical

Question 11

What are the vertical elements of softwoods called?

Answer 11

Trachieds

Question 12

What’s the function of trachieds?

Answer 12

In softwoods they’re arranged geometrically to allow liquid sap to pass through the

Question 13

What do the vertical elements in hardwoods do?

Answer 13

Vary in size and are made up of fibres with very thick walls to support the trees

Question 14

What is the main constituent of timber?

Answer 14

Cellulose

Question 15

What is lignin?

Answer 15

Chain molecules that are intermeshed with cellulose

Question 16

What 4 properties make timber a good choice for light structures?

Answer 16

Tensile strength is one direction
Lightweight
good in bending
strength/weight ratio is good

Question 17

What is the coefficient of thermal expansion of wood?

Answer 17

3.8 x 10^-6 mm/celcius

Question 18

What are the three different orientations of wood fibres?

Answer 18

Longitudinal
radial
Tangenital

Question 19

What greatly affects woods properties?

Answer 19

Water

Question 20

How does increasing water content affect wood?

Answer 20

Lowers its strength

Question 21

What kind of tension does wood work well under and why?

Answer 21

Uni-axial due to the high strength of cellulose micro-fibris

Question 22

What are the four types of failure in tension parallel to the grain?

Answer 22

Splintering tension
Combined tension and shear
Shear
Brittle tension

Question 23

What are the 3 types of failure in tension perpendicular to the grain

Answer 23

Tension failure of earlywood
Shearing along a growth ring
Tension failure of wood rays

Question 24

What are the 6 types of failure of nonbuckling wood

Answer 24

crushing
wedge splitting
shearing
splitting
crushing and splitting
brooming or end rolling

Question 25

Failure types in bending with span parallel to the grain

Answer 25

simple tension cross-grain tension splintering tension brash tension compression horizontal shear

Question 26

Which type of wood loses moisture content faster once felled?

Answer 26

Softwood

Question 27

How much water in wet wood is chemically bound?

Answer 27

20-30%

Question 28

What is free water?

Answer 28

Water held in the cell cavities

Question 29

What is bound water?

Answer 29

Water contained within the cell wall