Republic of the Philippines
Central Luzon State University
COLLEGE OF ENGINEERING
Science City of Muñoz, Nueva Ecija
DEPARTMENT OF AGRICULTURAL AND BIOSYSTEMS ENGINEERING
Laboratory Exercise 6
MECHANICAL
PROPERTIES OF WOOD
Prepared by:
CORREA, ALTHEA MAE C.
Student
Submitted to:
ENGR. ELMAN TORRES
Instructor
11/21/2019
I. INTRODUCTION
Wood has been used for thousands of years for fuel, as a construction material, for
making tools and weapons, furniture and paper. More recently it emerged as a feedstock
for the production of purified cellulose and its derivatives, such as cellophane and
cellulose acetate.
Some basic characteristics of wood has always been and continues to be a material of
great importance to mankind. It is highly versatile. It is relatively light in weight, yet has
good strength in both tension and compression; and provides rigidity, toughness and
insulating properties.
The production and processing of wood uses much less energy – known as embodied
energy – than most other building materials, giving wood products a significantly lower
carbon footprint. As a result wood can be used as a low-emission substitute for materials
that require larger amounts of fossil fuels to be produced.
The mechanical properties of wood considered in this book are: (1) stiffness and
elasticity, (2) tensile strength, (3) compressive or crushing strength, (4) shearing strength,
(5) transverse or bending strength, (6) toughness, (7) hardness, (8) cleavability, (9)
resilience.
II. OBJECTIVES
After performing the exercise, the student should be able to:
1. be knowledgeable on the mechanical properties of wood;
2. enumerate mechanical properties of wood; and
3. be familiar with the natural characteristics affecting mechanical properties of
wood.
IV. PROCEDURE
1. Make a wide research on the mechanical properties of wood
2. Describe the elastic properties of wood.
3. Enumerate and define the strength properties of wood.
4. Enumerate and define the natural characteristics affecting mechanical properties
of wood.
V. RESULTS AND DISCUSION
The table below are the examples of wood with their different mechanical
properties.
Modulus Shear
Fibre Stress at Compressive Strength parallel
Density of Strength parallel
Elastic Limit to Grain
-ρ- Elasticity to grain
Wood - σy - -σ-
(kg/m3) -E- -τ-
(MPa) (MPa)
(GPa) (MPa)
Alder, red 410 68 9.5 40.1 7.4
Ash - Black,
Blue, Green, 490 -
87 - 103 9.4 – 12 41.2 - 51.1 10.8 - 14
Oregon, 600
White
Aspen -
Bigtooth, 390 63 9.9 36.5 7.4
Quaking
Baldcypress 460 73 9.9 43.9 6.9
Baswood,
370 60 10.1 32.6 6.9
American
Beech,
640 103 11.9 50.3 13.9
American
Birch - Paper, 550 -
85 - 114 11 – 15 39.2 - 58.9 8.3 - 15.4
Sweet, Yellow 620
Butternut 380 56 8.1 36.2 8.1
Cedar -
Atlantic
White, 310 -
45 - 88 5.5 - 11.7 27.3 - 43.5 5.5 - 9.4
Eastern Red, 470
Incence,
Northern
Modulus Shear
Fibre Stress at Compressive Strength parallel
Density of Strength parallel
Elastic Limit to Grain
-ρ- Elasticity to grain
Wood - σ y - -σ-
(kg/m3) -E- -τ-
(MPa) (MPa)
(GPa) (MPa)
White, Port-
Orford,
Western Red,
Yellow
Cherry, black 500 85 10.3 49 11.7
Chestnut,
430 59 8.5 36.7 7.4
American
Cottonwood -
310 -
Balam Poplar, 27 - 59 7.6 - 9.4 27.7 - 33.9 5.4 - 7.2
400
Black, Eastern
Douglas-fir -
Coast, Inerior
460 - 10.3 -
West, Interior 82 - 90 43.1 - 51.2 7.8 - 10.4
500 13.4
North, Interior
South
Elm, English 560 40 - 54 11.8 17 - 32 8 - 11.3
Elm, Dutch 560 42 - 60 7.7 18 - 32 7.2 - 10
320 -
Fir 61.4 - 75.8 8.9 - 11.9 33.5 - 44.2 6.2 - 8.4
430
Hackberry 530 76 8.2 37.5 11
Hemlock - 400 -
61 - 79 8.3 - 11.3 37.3 - 49 7.3 - 10.6
Eastern, 450
Modulus Shear
Fibre Stress at Compressive Strength parallel
Density of Strength parallel
Elastic Limit to Grain
-ρ- Elasticity to grain
Wood - σ y - -σ-
(kg/m3) -E- -τ-
(MPa) (MPa)
(GPa) (MPa)
Mountain,
Western
Hickory,
pecan -
600 - 11.7 -
Bitternut, 94 - 123 47.6 - 62.3 14.3
660 13.9
Nutmeg,
Pecan, Water
Hickory, true -
Mockernut,
690 - 14.9 -
Pignut, 125 - 139 55.2 - 63.5 12 - 16.8
720 15.6
Shagbark,
Shellbark
Honeylocust 101 11.2 51.7 15.5
Larch,
520 90 12.9 52.5
Western
Locust, black 690 134 14.1 70.2 17.1
Magnolia -
480 -
Cucumbertree, 77 - 85 9.7 - 12.5 37.6 - 43.5 9.2 - 10.5
500
Southern
Mahogany 545 60 8.7 45 6.0
Maple -
Bigleaf, 480 -
61 - 109 7.9 - 12.6 36 - 54 11.9 - 16.1
Black, Red, 630
Silver, Sugar
Modulus Shear
Fibre Stress at Compressive Strength parallel
Density of Strength parallel
Elastic Limit to Grain
-ρ- Elasticity to grain
Wood - σ y - -σ-
(kg/m3) -E- -τ-
(MPa) (MPa)
(GPa) (MPa)
Oak, red -
Black,
Cherrybark,
laurel,
590 - 10.3 -
Northern Red, 75 - 125 42 - 60.3 9.6 - 14.3
690 13.1
Pin, Scarlet,
Southern Red,
Water,
Willow
Oak, white -
Bur, Chestnut,
Live,
Overcup, Post, 640 -
71 - 127 7.1 - 13.7 41.8 - 61.4 10.3 - 13.8
Swamp 880
Chestnut,
Swamp
White, White
Pine - Eastern
White, Jack,
Loblolly, 350 -
59 - 100 8.5 - 13.7 33.1 - 49.2 6.1 - 10.4
Lodgepole, 590
Longleaf,
Pitch
Poplar,
420 70 10.9 38.2 8.2
Yellow
Sassafras 460 62 7.7 32.8 8.5
Spruce - 350 -
Black, 63 - 79 7.9 - 11 37 - 44 6.8 - 9.2
430
Engelmann,
Modulus Shear
Fibre Stress at Compressive Strength parallel
Density of Strength parallel
Elastic Limit to Grain
-ρ- Elasticity to grain
Wood - σ y - -σ-
(kg/m3) -E- -τ-
(MPa) (MPa)
(GPa) (MPa)
Red, Sitka,
White,
Norway
Sweetgum 520 86 11.3 43.6 11
Sycamore,
490 69 9.8 37.1 10.1
American
Tupelo -
500 66 8.3 - 8.7 38.1 - 40.8 9.2 - 11
Black, Water
Walnut, black 550 101 11.6 52.3 9.4
Willow, black 390 54 7 28.3 8.6
ELASTIC PROPERTIES OF WOOD
In the simplest terms, the modulus of elasticity (MOE) measures a wood’s stiffness, and
is a good overall indicator of its strength.
Modulus of elasticity (MOE) testing
Technically it’s a measurement of the ratio of stress placed upon the wood compared to
the strain (deformation) that the wood exhibits along its length. MOE is expressed in
pounds-force per square inch (lbf/in2) or gigapaschals (GPa). This number is given for
wood that has been dried to a 12% moisture content, unless otherwise noted.
In practical terms, the number itself isn’t all that meaningful, but it becomes useful to use
in comparison with other woods. For instance, Hickory is known to have excellent
strength properties among domestic species in the US, and has a MOE of 2,160,000
lbf/in2 (14.90 GPa). In comparison, Red Oak is another well-known wood used in
cabinetry and furniture, and has a MOE of 1,820,000 lbf/in2 (12.50 GPa).
STRENGTH PROPERTIES OF WOOD
The strength of wood increases as its density increases. When evaluating the density of
wood, the level of moisture in which its mass and volume were measured must always be
known. Most commonly the density of wood is given as dry air density, whereby the
mass and volume of the wood are measured with its level of moisture at 15% (or 12%).
Density is often also given as a dry-fresh density, whereby the mass of the wood is
measured dry, and the volume saturation point (about 30%) at a high level of moisture.
The main tree species in Finland are pine, spruce and birch. Pine and spruce are the most
common in construction. The density of Finnish pine is 370 – 550 kg/m3, spruce 300 –
470 kg/m3 and birch 590 – 740kg/m3.
In the growth rings of a tree, there is much less lighter-coloured spring wood than
darker summer wood. In a normal pine tree, the share of summer wood is on average
25% and in spruce about 15%. In Finnish conifers in terms of wood strength, the ideal
gap between growth rings is 1-1.5 mm, under which circumstances the relative share of
summer wood in the growth rings is greatest. A small gap between rings does not
necessarily mean that the wood is denser and stronger. For example, the annual growth of
pines in Lapland is almost exclusively the rarer spring wood, even though the gap
between growth rings is very small. Because of this, a pine that has grown in Northern
Finland is lower in density and its timber lighter than a pine grown in Central and
Southern Finland.
The durability of the heartwood is not dependent on density because, in Finnish pine,
spruce and birch, the density of the wood increases as you go from the core to the
surface. The durability of the heartwood depends on a high resin content, which increases
its resistance to decay and pests. In the main Finnish trees, the density and strength of the
wood decreases as you go from the base to the top.
Natural Characteristics Affecting Mechanical Properties
Clear straight-grained wood is used for determining fundamental mechanical
properties; however, because of natural growth characteristics of trees, wood products
vary in specific gravity, may contain cross grain, or may have knots and localized slope
of grain. Natural defects such as pitch pockets may occur as a result of biological or
climatic elements influencing the living tree. These wood characteristics must be taken
into account in assessing actual properties or estimating the actual performance of wood
products.
VI. CONCLUSION
Therefore, I conclude that in this laboratory exercise I learned how to be
knowledgeable on the mechanical properties of wood, enumerate mechanical
properties of wood and be familiar with the natural characteristics affecting
mechanical properties of wood.
VII. REFERENCES
https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/ch04.pdf
https://www.woodproducts.fi/content/wood-a-material-1
https://www.engineeringtoolbox.com/timber-mechanical-properties-d_1789.html
