Wood

Question 1

How much of UK wood is imported

Answer 1

66%. It produces only around 16 million m^3 but uses 50 million m^3 annually

Question 2

What is softwood used for and where is it primarily sourced

Answer 2

construction, from Scandanavia

Question 3

What is hardwood used for and where is it primarily sourced

Answer 3

Furniture and interior design from eastern and western Europe as well as North America

Question 4

What is tropical wood used for

Answer 4

Marine construction + high value interiors

Question 5

Advantages of wood

Answer 5

high compressive and tensile strength, readily available, lightweight, relatively cheap, good thermal insulator, aesthetic, can be sustainable

Question 6

Disadvantages of wood

Answer 6

variability in performance, planes of weakness, can rot, contains inherent flaws, significant waste produced, requires transporting as wood is not often grown near the places it is used, can burn. (but predictable)

Question 7

why is wood the most sustainable material

Answer 7

Harvested from trees that can be regrown and suck carbon dioxide out of the air. Also is low in embodied energy and can be burnt for more energy, releasing only the amount of co2 it absorbed.

Question 8

Why are European Forests Growing despite the increase in the wood industry

Answer 8

More trees are being planted than they are harvested. The total European forest land grows at a rate of 3500 square miles annually

Question 9

What is the composition of dry wood by percentage and give their function

Answer 9

cellulose 50% microfibre, hemicellulose and pectin 20% matrix, lignin 25% matrix, extractives 5% toxicity

Question 10

why type of linkages form between cellulose

Answer 10

beta 1,4 bonds between glucose monomer (recall glucose has 6 carbons from the carbon attached to an oxygen and OH group going clockwise) and a lot of H bonds between the strands of cellulose

Question 11

Why is lignin not biodegradable

Answer 11

It is formed from phenyl propane which has a strong and unreactive carbon chain

Question 12

What must be done to wood before it can be used

Answer 12

Dried from 80% water content to about 20% by air or kiln drying

Question 13

Microstructure of wood

Answer 13

hygroscopic (absorbs moisture), discontinuous, anisotropic, inelastic, fibrous, porous, biodegradable,
longitudinal cells, similar to a bunch of closely packed straws

Question 14

What is the structure of wood

Answer 14

heartwood in the inside and sapwood on the outside. These vary in durability, permeability and colour sometimes but not strength

Question 15

What are some flaws that affect the strength of wood

Answer 15

fissure, knot, wane, growth rings

Question 16

Establish the strength along and across grain for tension, compression and shear

Answer 16

along grain - strong in tension and compression but weak in shear
across grain -weak in tension and compression but strong in shear

Question 17

How can we tell wood is not a brittle material

Answer 17

The crack propagates in a different direction

Question 18

Why is the loading and unloading curve of wood not the same

Answer 18

Wood behaves non elastically after a while and becomes viscoelastic due to the amorphous nature of lignin

Question 19

what is the benefit of using structural wood composites

Answer 19

Reduced variability in strength (but not necessarily increased strength) and increased dimensional stability, allows formation of shapes that are not normally possible with normal cut wood

Question 20

What are some examples of structural timber products

Answer 20

glulam, laminated veneer lumber and parallel strand lumber

Question 21

What is the biggest advantage of timber frame house building

Answer 21

It has a faster construction time

Question 22

What is the biggest advantage of timber frame house building

Answer 22

It has a faster construction time