Properties & Structure of Wood Flashcards
What are the characteristic properties of timber
- Low density and relatively high tensile strength
- Subject to dimensional changes due to variation in moisture content.
- Combustibility
- Anistropy due to fibrous nature of wood. material has different properties in different directions.
- Mechanical properties are fixed by the growth cycle.
What the three main functions of tree trunks
- Support the crown
- conduct mineral solutions from the roots to crown
- transport food from the crown and store it.
What is the outer region of a tree trunk called
Sapwood
Sapwood is the…
Outer region of a tree trunk
conduction of fluids and food storage are restricted to the…
Sapwood, outer region.
The inner region of a tree trunk is called…
Heartwood
Heartwood is…
The inner region of a tree trunk
What are observed in trunk cross-sections…
Growth rings
How to growth rings become annual
If trees are in temperature regions resulting from distinct seasons.
Growth rings occur because…
Different growth rates in different parts of the growing season.
What are the two different types of wood associated to different seasonal growth rates…
- Early Wood, softer coarser and more porous.
- Late Wood
What are the two classifications of commercial timber…
- Softwood
- Hardwood
Softwood and Hardwood are classified by…
Structural differences and not the mechanical properties
What type of tree are softwoods derived from…
Coniferous
Coniferous trees produce…
Softwood
What is the characteristic of coniferous trees…
needle shaped leaves (gymnosperms)
What type of tree are hardwoods derived from…
Broad leaved trees
Broad leaved trees produce…
Hardwoods
Trees which shed their leaves annually are called
Angiosperms
What are the four main types of cells in timber
(P) - Parenchyma
(T) - Tracheids
(F) - Fibres
(V) - Vessels
What is the function of Tracheids
they conduct fluids and contribute to mechanical support.
Needle shaped cells 2-5mm long which occur parallel to the stem axis.
they conduct fluids and contribute to mechanical support.
Needle shaped cells 2-5mm long which occur parallel to the stem axis.
Are the characteristics of…
Tracheids
What is the function of Parenchyma
They store food. occur n the rays and are block like cells
They store food. occur n the rays and are block like cells. Is the characteristic of…
Parenchyma
What is the function of fibres…
Support. long thin cells.
What cell type is responsible for support
Fibres
What is the function of Vessels…
Conduction. they are short relatively wide cells placed on top of each other.
What cell types to softwoods consist of…
Parenchyma
Tracheids
Parenchyma & Tracheids are consistent with…
Softwoods
Hardwoods have all four cell types because…
they are broad leaved tress which have to support a greater mass due to foliage.
What are the three sides of a wedge shapes piece of timber sample
Transverse - Top section
Radial - Side section going into centre
Tangential - Front facing side.
Vessels formed early on in growing season are wider and thinner, and the decease in size throughout the growth ring is slow. These species of tress are known as…
Diffuse-Porous hardwoods (beech, sycamore)
Diffuse-Porous hardwoods (beech, sycamore) are formed due to…
Vessels formed early on in growing season are wider and thinner, and the decease in size throughout the growth ring is slow
The abrupt transition from large vessels of the early wood to the small vessels of the late wood create…
Ring-porous hardwoods (oak, ash, elm)
Ring-porous hardwoods (oak, ash, elm) are formed due to…
The abrupt transition from large vessels of the early wood to the small vessels of the late wood
The structure of the cell wall consists of what components
Fibre & Matrix
What is the constituent of the fibre
Cellulose
Cellulose is a constituent of..
The Fibre.
What are the constituents of the Matrix
Lignin & Hemicelluloses
Lignin & Hemicelluloses are the constituents of…
The Matrix.
