Timber
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The vessel cell walls begin to dry out when the moisture content of the timber falls below what %?
28%
The vessel cells are made of?
Cellulose
Approximately how much timber is used as construction timber?
60%
Name three engineered timber products
I-beam, Plywood (glues together - glued laminated sections ‘’glulam’’), MDF, Laminated timber, Blockboard, Particleboard, Fibreboard, Wood wool slabs, Shingles, Compressed straw bales, Thatch
What requirements are needed for wood-rotting fungi to grow?
Moisture (at least 20%), oxygen and supply of food
Air drying of timber in the UK can reduce moisture levels but only down to about what %?
20%
During their larval stage, wood-boring beetles typically bore through timber for a period of?
2 years
Which is the least dense timber?
Balsa (200kg/m3)
The process of cutting tree trunks into planks is called?
Conversion - sawing of the timber. Happens before Seasoning. Two other processes are peeling (used in making plywood) and slicing (used to make decorative veneers).
The process of allowing timber to dry out to a moisture level similar to its intended surroundings is?
Seasoning - during seasoning (type of drying process) moisture is lost and the moisture content falls to about 28%. Removes moisture but NOT ALL moisture!!
The density of earlywood compared with the density of latewood is?
Lower
Seasoning is the process of?
Removing water from the timber
Moisture movement in timber is maximum in?
The tangential direction
Before rotting fungi can grow, timber must have a moisture content of at least what %?
20%
The effect of the Earth’s forests on the atmosphere is called?
A carbon sink - Timber absorbs CO2 (Carbon dioxide) and breathes out O2 (Oxygen)
It is easier to split timber?
Along the grain - Properties such as stiffness (E), compressive strength and tensile strength depend on directions – whether its parallel or perpendicular to the grain
The main cause of insect attack in UK timber comes from?
Beetles - lay their eggs on timber
Which is the densest of timbers?
Beech (750kg/m3)
Timber is classed into what 2 classes
Hardwood and Softwood - further onto earlywood (porous) and latewood (more dense)
What kind of resource is Timber?
Renewable - but consumption is constantly decreasing due to environmental reasons
Name different uses for Timber
Timber roofs, footbridge, docks, foundations and other concrete technology, kitchens - furniture
Is Timber Anisotropic in, 1, 2 or 3 directions?
3 directions - longitudinally (top-bottom of the trunk), radially (centre - outer bark), circumferentially (direction - around the trunk)
When the tree is growing what is happening to the vessel cells?
They are full of moisture but they DO NOT move (shrink or swell when full of sap)
Vessel Cells provide what to the timber?
Strength and Stiffness - as well as transport water up the tree in the early growing season each year