LABO CAMPUS - COLLEGE OF AGRICULTURE AND NATURAL RESOURCES
LESSON 2 ON MATERIALS AND PROCESS FOR ABE (AG-Eng1) for BSABE 2A & 2B
B. Construction Materials
B.1. Metals- This type of materials has characteristics like, high electrical and thermal
conductivity, the ability to be deformed or cut into new shapes without breaking, and high
mechanical strength. Since metals must be reduced from chemical compounds, they tend to be
somewhat more costly than non-metallic materials, and they are often vulnerable to corrosion
damage as the metals react with their environment to re-form those compounds. They tend to
be shiny and malleable. Metals have these characteristics because they have nonlocalized
electrons.
Steel is a metal alloy of iron and carbon and often other alloying material in its composition to make it
stronger and more fracture-resistant than iron. Stainless steels resist corrosion and oxidation because of
the additional chromium in their make-up. Because it is so strong compared to its weight and size,
structural engineers use it for the structural framework of tall modern buildings and large industrial
facilities. Some of its qualities include:
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Steel has high strength-to-weight and strength-to-size ratios.
It’s high-cost relative to other metals. Structural engineers can consult on choosing the most costeffective sizes to use in a house to support the actual load on the building.
Steel is less time-consuming to install than concrete.
It can be installed in any environment.
Steel can be susceptible to corrosion if improperly installed or maintained
Chrome, gold, and silver are generally used for finishes or decoration because they lack the tensile
strength of steel.
B.2. Wood - Among the oldest, or perhaps the oldest, of building materials, wood has been used for
thousands of years and has properties that make it an ideal building material—even in the days of
engineered and synthetic materials.
For construction use, wood pieces are machine-planed and cut into standard dimensions, such as 2”x4”
(1.5”x3.5” actual) and 2”x6,” (1.5”x5.5” actual) so that their measurements can be accurately factored into
building plans—this is known as dimensional lumber. Wood in larger sizes is usually referred to as timber
or beams and is often used to construct the frames of large structures like bridges and multi-story
buildings.
Some tree species are better for some uses and for use in some climates than others. Structural
engineers and architects can determine which type of wood is ideal for a construction project.
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It is readily available and an economical natural resource.
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Wood is relatively lightweight and easy to standardize in size.
It provides good insulation, which is why many architects and engineers like using it for homes
and residential buildings.
Wood has high tensile strength—keeping its strength while bending—and is very strong when
being compressed vertically.
Because it is lightweight and needs to be pressure treated to come into contact with surrounding
soil, wood is a less popular choice for foundations or basement walls. (However, permanent wood
foundations, known as PWFs, are gaining traction among builders thanks to the warm and inviting
wood basement living space they offer.) More often, wood-framed homes usually have a
reinforced concrete or pier and beam foundations.
are generally compounds between metallic and nonmetallic elements and
include such compounds as oxides, nitrides, and carbides. Typically they are insulating (not
electrical or thermally conductive) and resistant to high temperatures and harsh
environments (corrosion resistant). They usually have lower electrical and thermal
conductivity, higher stiffness, good resistance to corrosive environments, and lower fracture
toughness than metals. With the exception of glasses, ceramics usually cannot be reshaped
easily. To shape a ceramic, a mixture of ceramic powders, water, and binder materials is
molded into the desired dimensions to form a temporary shape. These temporary shapes
called "green bodies" are then dried to remove water and heated to allow the binder materials
to oxidize, leaving the ceramic powder particles to bond to each other during the high
temperature baking.
Ceramic engineering is the science and technology of creating objects from
inorganic, non-metallic materials. This is done either by the action of heat, or at lower
temperatures using precipitation reactions from high-purity chemical solutions.
B.3. Ceramics-
B.4. Polymers-Plastics (or polymers) are generally organic compounds based upon carbon
and hydrogen. They are very large molecular structures. Usually they are low density and are
not stable at high temperatures. They can be readily formed into complex shapes. Their
strength, stiffness, and melting temperatures are generally much lower than those of metals
and ceramics. Their light weight, low cost, and ease of forming make them the preferred
material for many engineering applications.
B.5. Composites - a combination of two or more materials differing in form or composition.
The differnet parts still have the same features they originally did, that is, they do not dissolve
or merge completely into one another, however, their properties are enhanced by each other.
Normally, the components can be physically identified and exhibit an interface (boundary)
between one another. Fiberglass, a combination of glass and a polymer, is an example.
Concrete and plywood are other familiar composites. Many new combinations include ceramic
fibers in metal or polymer matrix.
Corrosion is the destructive attack of a material by reaction
with its environment. The serious consequences of the
corrosion process have become a problem of worldwide
significance. In addition to our everyday encounters with this
form of degradation, corrosion causes plant shutdowns, waste
of valuable resources, loss or contamination of product,
reduction in efficiency, costly maintenance, and expensive
overdesign. It can also jeopardize safety and inhibit
technological progress.
Step 1 iron + oxygen --> iron oxide
Step 2 iron oxide + water --> hydrated iron oxide (rust)
Corrosion is the atmospheric oxidation of
metals. That means that oxygen combines
with the metal and forms a new layer. This
layer can be good or bad. By far the most
important form of corrosion is the rusting
of iron and steel. Rusting is a process of
oxidation in which iron combines with
water and oxygen to form rust, the
reddish-brown crust that forms on the
surface of the iron. Because iron is so
widely used, e.g., in building
construction and in tools, its protection
against rusting is important. Rusting can
be prevented by excluding air and water
from the iron surface, e.g., by painting,
oiling, or greasing, or by plating the
iron with a protective coating of another
metal. Many alloys of iron are resistant
to corrosion. Stainless steels are alloys
of iron with such metals as chromium and
nickel; they do not corrode because the
added metals help form a hard, adherent
oxide coating that resists further attack.
Although metals like aluminum, chromium, and zinc corrode more
readily than iron, their oxides form a coating that protects
the metal from further attack. Rust is brittle and flakes off
the surface of the iron, continually exposing a fresh surface.
Thus these metals might be a better selection choice for a
product that will be exposed to rusting conditions, like water
and air.
Recognizing the symptoms and mechanism of a corrosion problem
is an important preliminary step on the road to finding a
convenient solution. There are basically five methods of
corrosion control:
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Change to a more suitable material
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Modifications to the environment with the use of
inhibitors
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Use of protective metallic or organic coatings
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Design modifications to the system or component
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Provide adequate ventilation and drainage to
minimize the accumulation of condensation
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Avoid depressed areas where drainage is
inadequate
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Avoid the use of absorptive materials (such as
felt, asbestos and fabrics) in contact with
metallic surfaces)
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Prepare surfaces adequately prior to the
application of any protective coating system.
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Provide easy access for the purposes of corrosion
inspection and maintenance work
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Information care of Corrosion-doctors for more information
about:
Specific Corrosion of Metals, Theory of Corrosion, or a
Corrosion Glossary click on link
Choosing the right process
It is all very well to choose the perfect material, but somehow we
have to make something useful out of it! An important part of
understanding a product is to consider how it was made - in other
words what manufacturing processes were used and why. There are
2 important stages to selecting a suitable process:
Technical performance: can we make this product with the material and can we make it
well?
Economics: if we can make it, can we make it cheaply enough?
To find out about the different processing of materials click on the
following button, click on the process you want to find out about on the
left, and then read about it on the right, make sure you also click on the
four icons (Overview, Materials and Shapes, Economics, and Typical
Products) above each description :
Conductivity is the measure of the ease at which an electric charge or
heat can pass through a material. A conductor is a material which gives
very little resistance to the flow of an electric current or thermal energy.
Materials are classified as metals, semiconductors, and insulators.
Metals are the most conductive and insulators (ceramics, wood, plastics)
the least conductive.
Electrical conductivity tells
us how well a material will
allow electricity to travel
through it. Many people think
of copper wires as something
that has great electrical
conductivity.
Thermal conductivity tells us the ease upon which thermal energy
(heat for most purposes) can move through a material. Some materials
like metals allow heat to travel through them quite quickly. Imagine that
with one hand you are touching a piece of metal and with the other, a
piece of wood. Which material would feel colder? If you said, "metal,"
you would be correct. But, in fact, both materials are in fact the same
temperature. This is relative thermal conductivity. Metal has a higher
heat transferability, or thermal conductivity, than wood, letting the heat
from your hand leave faster. If you want to keep something cold the best
idea is to wrap it in something that does not have a high heat
transferability, or high thermal conductivity, this would be an insulator.
Ceramics, and polymers are usually good insulators, but you have to
remember that polymers usually have a very low melting temperature.
That means if you are designing something that will get very hot the
polymer might melt, depending on its melting temperature.
Electrical and thermal conductivity are closely
related. For the most part good electrical conductors
are also good thermal conductors.
Many products will contain both conductors and
insulators- the conductors take the electricity or
thermal energy where it is wanted and the insulators
prevent it from getting where it isn't wanted.
Silver has the highest electrical conductivity of all
metals. In fact, silver defines conductivity - all
other metals are compared against it. On a scale of
0 to 100, silver ranks 100, with copper at 97 and
gold at 76. Because of this property, and because it
doesn't spark easily, silver is commonly used in
electrical circuits and contacts. Silver is also
utilized in batteries where dependability is
mandatory and weight restrictions apply, such as
those for portable surgical tools, hearing aids,
pacemakers and space travel.
LINKS
http://www.physics4kids.com/files/elec_conduct.html
Lesson plan for teachers about conductivity- http://www.infinitepower.org/pdf/09-LessonPlan.pdf
Force is a push or a pull. Leaves and apples fall to the ground
because the force of gravity pulls them. When boys and girls
swing, sometimes a friend pushes them to help them get started.
This push is a force. When an airplane lands on a runway, the
force of gravity pulls it down toward the ground. When you open
or close a door, you are exerting a force on the door.
Check out these really fun tutorials from Building Big to get an idea of they types of
forces and how they affect different materials.
Now think about your product and how you're redesigning it,
think about the forces it is undergoing, are they compression,
tension, etc. and what materials work best for those kind of
forces. A hint is to think of the strength and the stiffness of
the original material, and make sure that you are at least as
strong and stiff as that material.
https://www.lehigh.edu/~amb4/wbi/kwardlow/WBIevidence.htm
Assignment:
1. Give example of each construction materials:
a. Metals
b. Woods
c. Ceramics
d. Polymers
e. Composites
2. Make Drawing or Pictures of each and discuss.
Prepared by:
DAVE Y. RIEZA, RPABE
Instructor