WOOD

ACS-206 WEEK 6 UNIT 17

CE-ME-MECE-MSE

Categories of Wood

• There are mainly two categories of wood:1. Hardwood2. Softwood

Categories of Wood

• Hardwood comes from deciduous, or hardwood, trees.

• Decidous trees lose their leaves in the fall.

• The tree on the right is a hardwood tree.

Categories of Wood

• Softwood comes from evergreen, or softwood, trees.

• Evergreen trees keep their leaves all year.

• The tree on the right is a softwood tree.

Categories of Wood

• In engineering, wood can be categorized as solid wood and engineered wood.

Categories of Wood

• Solid wood – softwood or hardwood that has been sawn into specific shapes and sizes, but whose natural structure, consisting of grain and knots, remains intact.

solid wood coffee table

Categories of Wood

grain

Categories of Wood

• Engineered wood – made by bonding (sticking together) layers of solid softwood or harwood, or by mixing quantities of wood particles and bonding them with resin.

engineered flooring

Solid Structural Timber• Solid structural timber

= wood intended to support loads in a structure.

Solid Structural TimberTimber is cut to the required section – the width and depth that determine its cross-section – at a sawmill, where a range of section sizes are produced.

section sawmill

Solid Structural TimberTimber from sawmills is generally supplied in rough-sawn sections. This refers to the surface texture produced by sawing timber with a circular saw.

rough-sawn timber circular saw

Solid Structural Timber

• If the timber needs to have a smooth finish – for example, because it will be visible in the structure – it can subsequently be planed to smooth its surface.

Solid Structural Timber• Because the strength of wood

varies, structural timber must be stress-graded. This means its strength is tested in order to give it a stress grade – a standard strength value which an engineer can use for design calculations.

Solid Structural TimberTimber can be mechanically stress-graded, where its strength is checked by machine. It can also be visually stress graded, where the wood is examined by an inspector who looks for potential wekanesses – in particular, the position of the knots.

mechanical stress grading visual stress grading

Engineered Wood

• Engineered wood covers a range of softwood and hardwood materials. It includes:Cheap, low strength boards such as particle board

and medium density fibreboard (MDF)Stronger boards such as orientated strand board

(OSB) and plywoodGlulams (glue laminated sections)

Engineered Wood

• Particleboard(or chipboard) is a multi-purpose material and one of the most widely-used wood-based panels. Particle board is an engineered wood-based product manufactured from wood chip particles and a synthetic binding resin. It is formed in a press using heat and pressure.

Engineered Wood

• Medium density fibreboard (MDF) is a composite panel product typically consisting of cellulosic fibers combined with a synthetic resin or other suitable bonding system and joined together under heat and pressure. The surface of MDF is flat, smooth, uniform, dense and free of knots and grain patterns.

Engineered Wood

• Orientated strand board (OSB) is made from strands of wood bonded with resin. OSB is widely used in residential and commercial construction.

Engineered Wood

• Plywood consists of several plies (layers) of solid wood, bonded so that the grain of each ply runs at 90 degrees to that of the adjacent plies, to provide increased strength.

Engineered Wood

• Glued laminated timber (glulam) is an industrial wooden product for load bearing purposes. Glulam consists of at least three dried softwood boards, which are flatwise glued together.

CANKAYA UNIVERSITY - OFFICE OF BASIC AND ELECTIVE COURSES- ENGLISH UNIT