Formulae and Tables - Wood / textbooks for vocational training (GTZ, 122 p.) 2. Materials Made of Wood 2.1. Solid Wood (introduction...) 2.1.1. Not Improved Solid Wood 2.1.2. Improved Solid Wood 2.2. Laminated Wood 2.3. Sandwich Boards 2.4. Fibreboards 2.5. Particle Boards

Formulae and Tables - Wood / textbooks for vocational training (GTZ, 122 p.)

2. Materials Made of Wood

2.1. Solid Wood

Solid wood is obtained from raw wood by longitudinal and cross cutting. It is used without or after improvement of the wood.

2.1.1. Not Improved Solid Wood

Name	Definition	Remarks
round timber	Round timber is obtained from rough wood by cross cutting. It includes saw logs, veneer flitches, masts, poles and others.	Saw logs and veneer flitches are intermediate products which are intended for further cutting.
Sawn timber	Sawn timber is produced by longitudinal cutting of round timber. Sawn timber has at least 2 parallel surfaces and is thicker than 5 mm.	Making of simple cut and double cut; simple cut:
		single passage through the machine yields untrimmed products; double cut:
		two passages through the machine; first passage is precut, edge boards and slabs are cut off; second passage is second cut; from the material turned by 90° the trimmed product is obtained.
Veneer	Is produced by longitudinal cutting (slicing, sawing) or arcuate cutting-off (peeling) of round wood; veneer is £ 3 mm thick and ³ 80 mm broad.

Kinds of sawn timber

Kinds Schematic representation		Width in mm (b)	Thickness in mm (s)
squared timber		>100	>100
frame timber		£ 2s	38...100
board (1) round-edged	(2) edge-trimmed	round-edged ³ 2 s edge-trimmed ³ 75	>16 16...100
lath		>75	16...35
ply		edge-trimmed ³ 75	6...15
strip		or round-edged < 75	6...15

Kinds of veneers

Kinds Schematic representation	Manufacture
sliced veneer	Sliced veneers are made by slicing off lamella by lamella in an operation similar to planing. Effective strokes of the machine: 16...36 min-1 cutting speed: 0.5 to 1.5 m s-1 length: up to 5 m thickness: 0.05 to 2.7 mm
1 knife, 2 knife holder, 3 veneer, 4 pressure strip, 5 pressure bar
peeled veneer	Peeled veneers are taken from a rotating trunk by an operation similar to turning. cutting speed: 0.2 to 2.5 m · s-1 length: up to 4.5 m thickness: 0.08 - 2.7 mm
1 veneer knife, 2 knife holder, 3 veneer, 4 pressure strip, 5 pressure bar, 6 scratcher knife
saw veneer	Sawn veneers are produced with a horizontal frame saw or a veneer circular saw. Speed of the veneer frame saw: 200...300 min-1 cutting speed: 6...8 m · s-1 length: up to 5 m thickness: 0.5 to 3.0 mm
1 saw blade, 2 compression roll, 3 veneer, 4 cleaving knife

2.1.2. Improved Solid Wood

Kind of solid wood	Manufacture		Application
compressed solid wood	solid wood compressed by pressing, beating or rolling under the influence of pressure and temperature		machine parts in the textile industry, bearing shells, press-drawing tools, etc.
impregnated solid wood	solid wood impregnated with various agents (e.g. resin, oil, metal) for changing its properties		synthetic resin-impregnated timbers in electric engineering, oil-impregnated wood as self-lubricating machine parts, metal-impregnated wood as slide bearing
formed solid wood		solid wood formed under the influence of temperature, moisture and pressure (by applying pressure on the cross-grain ends of the blank the latter is compressed and thus made bendable)	for bent parts in furniture construction, in vehicle construction and boat building, for the manufacture of sports equipment etc.

2.2. Laminated Wood

Laminated wood consists of veneer layers which are symmetrically laid one on top of the other. It is glued together by means of adhesive under pressure and temperature to form sheet material. Laminated wood has improved properties compared with solid wood and can be used for many more purposes.

Name	Material construction	Physical quantities	Application
plies (plywood)	symmetrical arrangement of the veneer layers, the layers are staggered alternately 90° according to the grain direction	r = 0.60...075 g · cm-3 dzB =35...55 MPa ddB = 60...80 MPa dbB = 55...75 MPa	furniture industry, interior work, packaging industry, building industry etc.
laminated wood	veneers are arranged in parallel with each other (grain direction); up to 15 % vertically to it	r = 0.65...0.95 g · cm-3 dzB =80...170 MPa ddB = 70...110 MPa dbB = 120..200 MPa	aircraft manufacture, shipbuilding, vehicle construction, timber engineering etc.
compressed laminated wood	arrangement of the veneers is the same as with plywood or laminated wood; by applying pressures of about 10 MPa compression is achieved (10 %)	r = 0.80...1.15g · cm-3 dzB £ 220 MPa ddB £ 250 MPa dbB £ 250 MPa	machine parts, timber engineering, apparaturs construction, toolroom work, vehicle construction
plastic compressed laminated wood	same as compressed laminated wood, but made of synthetic resin-impregnated veneer	p = 1.15...1.35 g · cm-3 dzB £ 140 MPa ddB £ 300 MPa dbB £ 240 MPa	vehicle construction, electric engineering, apparatus construction, timber engineering, machine parts

2.3. Sandwich Boards

Sandwich boards consist of a core and two cover plies, one on each side. Compared to the solid starting material considerable savings in material are possible and improved properties are reached.

Name	Material construction	Physical quantities	Application
sandwich board with solid wood core		r = 0.42...0.52 g · cm-3 ddB = 12...38 MPa dbB = 30...40 MPa	furniture industry, interior work, pattern making, development working etc.
1 cover ply of crossband veneer; thickness ³ 1.8 mm 2 solid wood core of blackboard
sandwich board with hollow core		r = 0.01...0.04 g · cm-3 dzB = 1.7 MPa ddB = 2.9 MPa dbB = 14 MPa	doors, partition walls, vehicle construction and shipbuilding, interior work, boat building
1 outer layers of veneer, plywood, hard fibre boards, metal or plastic boards; 2 core of paper honeycombs
sandwich board with particle board core	Particle boards as cores are coated on both sides with veneer or synthetic resin-impregnated papers. In this way their properties and appearance are improved.	r = 0.7...0.8 g · cm-3 face strength » 0.9 MPa dbB » 40 MPa	furniture construction, interior work, ship building and waggon construction

2.4. Fibreboards

Fibreboards are a flat, sheet wood-based material made under the influence of pressure and temperature which consists of fibrous material cotaining lignocellulose.

Properties of fibreboards

Kind of board	Thickness in mm	Gross density r in g · cm-3	Bending strength dbB in MPa	Compressive strength ddB in MPa	Transverse tensile strength d in MPa
hardened fibreboards	1...6	1.0...1.1	60	50...60	30...55
hard fibreboards	1...6	0.95...1.05	25...75	25...50	15...40
medium hard fibreboards	6...25	30...75	10...40	80	8...25
porous fibreboards	6...20	25...40	1.0...3.0	0.8...2.0	1.0...3.0
medium-dense fibreboards	10...19	0.60...0.85	15...32		0.3...0.7

Use of the fibreboards

Kind of board	Special features	Applications
medium-dense fibreboards	three-layer structure, high surface quality, homogeneous core structure, closed homogeneous narrow surfaces	same as (three-layer) particle boards for furniture, especially for visible outer surfaces of furniture
porous fibreboards	low density, low strength, heat-insulating	ceilings and panellings, roof sheathing, floor underlay
medium-hard fibreboards	heat-insulating	partition walls, panellings, roof sheathing
hard fibreboards	uniform surface, elastic, bendable, nailing and screwing possible	ceiling boarding and panelling, furniture parts, doors, partition walls, coverings
hardened fibreboards	oil-impregnated, especially abrasion-proof, water-repellent	panelling and sheathing outdoors, inner and outer doors, concrete moulds, floor, staircase and table coverings
sound-absorbing boards	porous fibreboards provided with holes, slits or similar for sound absorption	ceiling boarding and panellings in offices, telephone exchanges, cinemas, concert halls etc.
multilayer insulating boards	boards consisting of two or more layers of porous fibreboards glued in a water-proof manner	partition walls, displaceable walls, false ceilings
varnished boards	hard fibreboards with varnish coating	panellings in kitchens, shops, bathrooms, for furniture in rooms in which water is handled
sheet and plastic-coated fibreboards	hard fibreboards coated with coloured plastic sheets or synthetic resin-impregnated special papers	panellings in kitchens and bathrooms, for furniture in damp rooms, for table coverings in kitchens, shops, workshops, laboratories etc.
embossed fibreboards	hard fibreboards which during manufacture were given an embossed surface and (possibly subsequently) a colour treatment	for decorative purposes in interior work
floor boards	extra hard fibreboards which are laid like parquet, high wear resistance	for floor coverings
hard multi-layer boards	boards consisting of two or more layers of subsequently glued medium-hard or hard fibreboards	panels, shock-resistant coverings, partition walls, false ceilings

2.5. Particle Boards

The particle board is a wood-based material made of wood chips with the addition of synthetic resin under the influence of pressure and temperature. Its properties can be varied by the kind and quantity of the additives, by the quality and arrangement of the chips and the compression ratio.

Properties of the particle boards

Kind of board	Thickness in mm	Gross density r in g · cm-3	Bending strength dbB in MPa	Transverse tensile strength r in MPa
single-layer flat pressed particle boards	6...25	0.5...0.85	15...20	0.2...0.3
triple-layer flat pressed particle boards	6...25	0.55...0.85	20...30	0.2...0.3
extruded particle boards	8...75	0.55...0.70	» 2.0 in pressing direction » 15.0 at right angles to the pressing direction	» 0.6 in pressing direction » 4.0 at right angles to the pressing direction

Use of the particle boards

Kind of board	Special features	Applications
flat pressed particle boards, raw, single-layer	dense surface, heat and sound-insulating, pressure-proof	interior work, building construction, agricultural building, floor underlays, insulating boards etc.
Flat pressed particle boards, raw multi-layer	like single-layer boards, but surface layer consisting of fine particles; dense surface, little swelling	manufacture of furniture, self-supporting structural elements, interior work, vehicle construction
extrusion particle boards, raw	low bending strength, coating absolutely necessary, in other aspects like single-layer boards	core for sandwich boards in furniture manufacture, in interior work, shipbuilding and vehicle construction, building industry
impregnated particle boards	additives are added to the binder, therefore resistant to temperature and wood pests	building industry, agricultural building, shipbuilding
veneer-coated particle boards	more resistant to varying climatic influences, better stability, higher bending strength	visible surface in furniture manufacture, interior work and shipbuilding, for panelling, cladding
particle boards coated with laminated boards, PVC-hard-boards or decorative laminates *)	coating on one side or both sides, higher strength, higher resistance to moisture and chemicals, scratch resistant	furniture in damp rooms, doors, partition walls, structural elements for walls, but also containers, concrete moulds, mainly in the kitchen furniture industry

*) decorative laminates: plastic sheets with wood pattern