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Soils And Materials Two > Timber 1 > Flashcards

Timber 1 Flashcards

1
Q

What are the three sub-systems of a tree?

A

Crown
Trunk
Root

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2
Q

What is bark?

A

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

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3
Q

What is bast?

A

The inner bark which carries enriched sap from leave to cells

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4
Q

What is cambium

A

Layer of living cells between the bast and the sapwood

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5
Q

What is sapwood?

A

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

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6
Q

What is heartwood?

A

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

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7
Q

What are annual/growth rings?

A

Layers inside the tree which show age

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8
Q

What trees do softwoods come from?

A

Evergreen coniferous trees

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9
Q

What are the 6 types of grains?

A

Diagonal
Straight
Irregular
Spiral
Wavy
Interlocked

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10
Q

What level of anisotropy does wood have?

A

90-95% of cells are elongated and vertical

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11
Q

What are the vertical elements of softwoods called?

A

Trachieds

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12
Q

What’s the function of trachieds?

A

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

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13
Q

What do the vertical elements in hardwoods do?

A

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

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14
Q

What is the main constituent of timber?

A

Cellulose

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15
Q

What is lignin?

A

Chain molecules that are intermeshed with cellulose

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16
Q

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

A

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

17
Q

What is the coefficient of thermal expansion of wood?

A

3.8 x 10^-6 mm/celcius

18
Q

What are the three different orientations of wood fibres?

A

Longitudinal
radial
Tangenital

19
Q

What greatly affects woods properties?

A

Water

20
Q

How does increasing water content affect wood?

A

Lowers its strength

21
Q

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

A

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

22
Q

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

A

Splintering tension
Combined tension and shear
Shear
Brittle tension

23
Q

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

A

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

24
Q

What are the 6 types of failure of nonbuckling wood

A

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

25
Q

Failure types in bending with span parallel to the grain

A

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

26
Q

Which type of wood loses moisture content faster once felled?

A

Softwood

27
Q

How much water in wet wood is chemically bound?

A

20-30%

28
Q

What is free water?

A

Water held in the cell cavities

29
Q

What is bound water?

A

Water contained within the cell wall

30
Q
A

Soils And Materials Two (5 decks)

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