Plywood

The material. Plywood is laminated wood, the layers glued together such that the grain in successive layers are at right angles, giving stiffness and strength in both directions. The number of layers varies but is always odd (3, 5, 7 …) to give symmetry about the core ply; if it is asymmetric it warps when wet or hot. Those with few plies (3, 5) are significantly stronger and stiffer in the direction of the outermost layers; with increasing number of plies the properties become more uniform. High-quality plywood is bonded with synthetic resin. The following data describes the in-plane properties of a typical five-ply.

Composition

Cellulose/hemicellulose/lignin/12%H2O/adhesive.

Plywood dominates the market for both wood and steel stud construction. It is widely used, too, for furniture and fittings, boat building, and packaging.

Ecoproperties: material
Embodied energy, primary production CO2 footprint, primary production Water usage Eco-indicator	13 0.73 *500 37	– 17 – 0.77 – 1000 – 41	MJ/kg kg/kg l/kg millipoints/kg
Ecoproperties: processing Construction energy Construction CO2	*0.455 *0.022	– 0.55 – 0.027	MJ/kg kg/kg
Recycling Recycle fraction in current supply	1	– 2	%

Typical uses. Furniture, building and construction, marine and boat build­ing, packaging, transport and vehicles, musical instruments, aircraft, modeling.

The material. Softwoods come from coniferous, mostly evergreen, trees such as spruce, pine, fir, and redwood. Wood must be seasoned before it is used. Seasoning is the process of drying to remove some of the natu­ral moisture to make it dimensionally stable. In air seasoning the wood is dried naturally in covered but open-sided structures. In kiln drying the wood is artificially dried in an oven. Wood has been used for construction and to make products since the earliest times. Timber continues to be used on a massive scale, particularly in housing and commercial buildings.

Composition

Cellulose/hemicellulose/lignin/12%H2O.

General properties

Density	440	– 600	kg/m3
Price	1.04	– 2.07	USD/kg

Mechanical properties

Young’s modulus Yield strength (elastic limit) Tensile strength Compressive strength Elongation Hardness—Vickers Fatigue strength at 107 cycles Fracture toughness

Wood remains one of the world’s major structural materials as well finding application in more delicate objects such as furniture and musical instruments.

Typical uses. Flooring; furniture; containers; cooperage; sleepers (when treated); building construction; boxes; crates and palettes; planing-mill products; subflooring; sheathing; and as the feedstock for plywood, particle­board, and hardboard.

The material. Softwoods come from coniferous, mostly evergreen, trees such as spruce, pine, fir, and redwood. Wood must be seasoned before it is used. Seasoning is the process of drying to remove some of the natu­ral moisture to make it dimensionally stable. In air seasoning the wood is dried naturally in covered but open-sided structures. In kiln drying the wood is artificially dried in an oven. Wood has been used for construction and to make products since the earliest times. Timber continues to be used on a massive scale, particularly in housing and commercial buildings.

Composition

Cellulose/hemicellulose/lignin/12%H2O.

General properties
Density	440	– 600	kg/m3
Price	1.04	– 2.07	USD/kg

Mechanical properties Young’s modulus	0.6	– 0.9	GPa
Yield strength (elastic limit)	*1.7	– 2.6	MPa
Tensile strength	3.2	– 3.9	MPa
Compressive strength	*3	– 9	MPa
Elongation	1	– 1.5	%
Hardness—Vickers	2.6	– 3.2	HV
Fatigue strength at 107 cycles	*0.96	– 1.2	MPa
Fracture toughness	*0.4	– 0.5	MPa. m1/2

Thermal properties
Glass temperature	77 –	102	°C
Maximum service temperature	120 –	140	°C
Thermal conductor or insulator?	Good insulator
Thermal conductivity	0.08 –	0.14	W/m. K
Specific heat capacity	1660 –	1710	J/kg. K
Thermal expansion coefficient	*26 –	36	p, strain/°C

Electrical properties Electrical conductor or insulator?	Poor insulator
Electrical resistivity	*2.1 X 1014 –	7 X 1014	pnhm. cm
Dielectric constant	*5 –	6.2
Dissipation factor	*0.03 –	0.07
Dielectric strength	1-	2 106	V/m

Wood remains one of the world’s major structural materials as well finding application in more delicate objects such as furniture and musical instruments.

Typical uses. Flooring; furniture; containers; cooperage; sleepers (when treated); building construction; boxes; crates and palettes; planing-mill products; subflooring; sheathing and as the feedstock for plywood, particle­board, and hardboard.

The material. Hardwoods come from broad-leaved, deciduous trees such as oak, ash, elm, sycamore, and mahogany. Although most hardwoods are harder than softwoods, there are exceptions: balsa, for instance, is a hard­wood. Wood must be seasoned before it is used. Seasoning is the process of drying the natural moisture out of the raw timber to make it dimensionally stable, allowing its use without shrinking or warping. In air seasoning the wood is dried naturally in covered but open-sided structures. In kiln drying the wood is artificially dried in an oven or kiln.

Composition

Cellulose/hemicellulose/lignin/12%H2O.

General properties

Density	850	– 1030	kg/m3
Price	3.11	– 4.15	USD/kg
Mechanical properties
Young’s modulus	20.6	– 25.2	GPa
Yield strength (elastic limit)	43	– 52	MPa
Tensile strength	132	– 162	MPa
Compressive strength	68	– 83	MPa
Elongation	*1.7	– 2.1	%
Hardness—Vickers	*13	– 15.8	HV
Fatigue strength at 107 cycles	*42	– 52	MPa
Fracture toughness	*9	– 10	MPa. m1′

Thermal properties

Glass temperature	77	– 102	°C
Maximum service temperature	120	– 140	°C
Thermal conductor or insulator?	Good insulator
Thermal conductivity	*0.41	– 0.5	W/m. K
Specific heat capacity	1660	– 1710	J/kg. K
Thermal expansion coefficient	*2.5	– 9	p, strain/°C

Electrical properties Electrical conductor or insulator? Poor insulator Electrical resistivity *6 X 1013 – 2 X 1014 pnhm. cm Dielectric constant *5 – 6 Dissipation factor *0.1 – 0.15 Dielectric strength *0.4 – 0.6 106 V/m

Wood remains one of the world’s major structural materials as well finding application in more delicate objects such as furniture.

Ecoproperties: material
Embodied energy, primary production	7.4	– 8.2	MJ/kg
CO2 footprint, primary production	0.45	– 0.49	kg/kg
Water usage	*730	– 1.5e3	l/kg
Eco-indicator	6.3	– 6.9	millipoints/kg
Ecoproperties: processing
Construction energy	*0.909	– 1.1	MJ/kg
Construction CO2	*0.045	– 0.05	kg/kg
Recycling
Recycle fraction in current supply	8	– 10	О/ %

Typical uses. Flooring; stairways, furniture; handles; veneer; sculpture; woodenware; sashes; doors; general millwork; framing—but these are just a few. Almost every load-bearing and decorative object has, at one time or another, been made from wood.

The material. Hardwoods come from broad-leaved, deciduous trees such as oak, ash, elm, sycamore, and mahogany. Although most hardwoods are harder than softwoods, there are exceptions: balsa, for instance, is a hard­wood. Wood must be seasoned before it is used. Seasoning is the process of drying the natural moisture out of the raw timber to make it dimensionally stable, allowing its use without shrinking or warping. In air seasoning the wood is dried naturally in covered but open-sided structures. In kiln drying the wood is artificially dried in an oven or kiln.

Composition

Cellulose/hemicellulose/lignin/12%H2O. General properties

Density	850	– 1.13e3 kg/m3
Price	3.11	– 4.15 USD/kg

Mechanical properties Young’s modulus	4.5	– 5.8	GPa
Yield strength (elastic limit)	*4	– 5.9	MPa
Tensile strength	7.1	– 8.7	MPa
Compressive strength	*12.7	– 15.6	MPa
Elongation	1	– 1.5	%
Hardness—Vickers	10	– 12	HV
Fatigue strength at 107 cycles	*2.1	– 2.6	MPa
Fracture toughness	*0.8	– 1	MPa. m1/2

Thermal properties Glass temperature	77	– 102	°C
Maximum service temperature	120	– 140	°C
Thermal conductor or insulator? Thermal conductivity	Good insulator 0.16 – 0.2	W/m. K
Specific heat capacity	1660	– 1710	J/kg. K
Thermal expansion coefficient	*37	– 49	p, strain/°C

Electrical properties Electrical conductor or insulator?	Poor insulator
Electrical resistivity	*2.1 x 1014 – 7 x 1014	pnhm. cm
Dielectric constant	*5 – 6
Dissipation factor	*0.1 – 0.15
Dielectric strength	*0.4 – 0.6 106	V/m

Wood remains one of the world’s major structural materials as well finding application in more delicate objects such as furniture.

Eco properties: material Embodied energy, primary production	7.4	– 8.2	MJ/kg
CO2 footprint, primary production	0.45	– 0.49	kg/kg
Water usage	*730	– 1.5e3	l/kg
Eco-indicator	6.3	– 6.9	millipoints/kg

Eco properties: processing
Construction energy	*0.909 – 1.1	MJ/kg
Construction CO2	*0.045 – 0.05	kg/kg
Recycling
Recycle fraction in current supply	8 – 10	%

Typical uses. Flooring; stairways, furniture; handles; veneer; sculpture, woodenware; sashes; doors; general millwork; framing—but these are just a few. Almost every load-bearing and decorative object has, at one time or another, been made from wood.

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