Aircraft Materials, Construction and Repair (Aircraft Metals)
Aircraft Structure
must be strong, lightweight, streamlined, and durable.
Wooden Monocoque Design
does provide a streamlined from with high strength, but with compromise due to the limited useful life of wood, as well as the high cost involved with fabric-catting a laminated wood structure.
Riveted or Bonded sheet
Today, the high volume of aircraft production has caused _________ or _________ designs to become the most common method of construction.
Aluminum Alloys
most widely used metal used for aircraft structures which account for as much as 90 % of the metals used for civil aircraft.
Heat-treated aluminum alloys
have the advantage of being lightweight with the ability to carry high structural loads, while being comparably inexpensive with regard to other similar strength metals.
titanium, stainless steel, and assorted exotic metals
These assets make aluminum alloy an excellent choice to use for the construction of most modern civil aircraft. The remaining 10% of metals used include _________, _________ and _________ that are predominantly used on military or large transport category aircraft.
Monocoque and Semi-Monocoque
What are the two basic types of sheet metal structures used for aircraft
Monocoque Construction
It is a structural system where loads are supported through an object’s external skin. It can support a large load if a force is applied evenly across the containers. Its downside is that with a small dent or crease in a side wall can destroy its ability to support load.
Semi-monocoque Construction
It refers to a stressed shell structure that is similar to a true monocoque, but which derives at least some of its strength from conventional reinforcement.
Semi-Monocoque airframe
It utilizes stringers and longerons to add rigidity and strength to the structure.
Hardness
Refers to the ability of a material to resist abrasion, penetration, cutting action, or permanent distortion. It may be increased by cold working the metal and, in the case of steel and certain aluminum alloys, by heat treatment.
Strength
It is the ability of the material to resist deformation and resist stress without breaking.
Density
It is the weight of a unit volume of a material. In aircraft work, the specified weight of a material per cubic inch is preferred since this figure can be used in determining the weight of a part before actual manufacture.
Malleability
A metal which can be hammered rolled, or pressed into various shapes without cracking, breaking, or leaving some other detrimental effect.
Ductility
It is the property of a metal which permits it to be permanently drawn, bent, or twisted into various shapes without breaking. This property is essential for metals used in making wire and tubing.
Elasticity
It is that property that enables a metal to return to its original size and shape when the force which causes the change of shape is removed. This property is extremely valuable because it would be highly undesirable to have part permanently distorted after an applied load was removed.
Toughness
A material which possesses toughness will withstand tearing or shearing and may be stretched or otherwise deformed without breaking. This is known to be desirable in aircraft metals.
Brittleness
Is the property of a metal which allows little bending or deformation without shattering. It is apt to break or crack without change of shape.
Fusibility
It is the ability of a metal to become liquid by the application of heat.
Conductivity
Is the property which enables a metal to carry heat or electricity.
Thermal Expansion
Refers to the contraction and expansion that are reactions produced in metals as the result of heating or cooling
Ferrous Metal
any alloy containing iron as its chief constituent.
Non-ferrous Metal
much of the metal used on today’s aircraft contains no iron. The term that describes metals which have elements other than iron as their base is _________.
Iron
It is a chemical element which fairly soft, malleable, and ductile in its pure form. It combines readily with oxygen to form iron oxide, which is more commonly known as rust.
rust
It is when iron is combine with oxygen to form Iron Oxide
Iron Oxide
also known as rust
Steel
pig iron is remelted in a special furnace. Pure oxygen is then forced through the molten metal where it combines with carbon and burns. A controlled amount of carbon is then put back into the molten metal along with other elements to produce the desired characteristics.
Pig Iron
What is reheated on a special furnace when making steel.
Carbon
The greater its content. the more receptive steel is to heat treatment and, therefore, the higher its tensile strength and hardness. However, higher carbon content decreases the malleability and weldability of steel.
Sulfur
causes steel to be brittle when rolled or forged and, therefore, it must be removed in the refining process. If this element cannot be removed its effects can be countered by adding manganese.
Phosphorus
raises the yield strength of steel and improves low carbon steel’s resistance to atmospheric corrosion.
Nickel
adds strength and hardness to steel and increases its yield strength. It also slows the rate of hardening when steel is heat-treated, which increases the depth of hardening and produces a finer grain structure.
Chromium
It is alloyed with steel to increase strength and hardness as well as improve its wear and corrosion resistance.
Society of Automotive Engineers (SAE)
An organization that has established standards for materials and processes that are widely use din aviation industry.
Aerospace Recommended Practices
are recommendations for engineering practice, and Aerospace Information Reports contain general accepted engineering data and information.
Carbon Steels
SEA Classification of Steel : 1XXX
Nickel Steels
SEA Classification of Steel : 2XXX
Nickel-Chromium Steels
SEA Classification of Steel : 3XXX
Molybdenum Steels
SEA Classification of Steel : 4XXX
Chromium Steels
SEA Classification of Steel : 5XXX
Chromium-vanadium Steels
SEA Classification of Steel : 6XXX
Tungsten Steels
SEA Classification of Steel : 7XXX
Nickel-Chromium-Vanadium Steels
SEA Classification of Steel : 8XXX
Silicon-Manganese Steels
SEA Classification of Steel : 9XXX
Aluminum
It is vital to the aviation industry because of its high strength to weight ratio and its comparative ease of fabrication.
Pure Aluminum
is light weight and corrosion resistant, but it lacks strength for use as a structural material.
Four Digit Index System
Aluminum and aluminum alloys are designated by a _______________ which is broken into three distinct groups: 1XXX group, 2XXX through 8XXX group. and 9XXX group (which is currently unused)
Aluminum
Wrought Alloy Designation System: 1XXX
Copper
Wrought Alloy Designation System: 2XXX
Manganese
Wrought Alloy Designation System: 3XXX
Silicon
Wrought Alloy Designation System: 4XXX
Magnesium
Wrought Alloy Designation System: 5XXX
Magnesium and Silicon
Wrought Alloy Designation System: 6XXX
Zinc
Wrought Alloy Designation System: 7XXX
Other Elements
Wrought Alloy Designation System: 8XXX
1100
99.00 percent pure aluminum with one control over individual impurities.
1130
99.30 percent pure aluminum with one control over individual impurities.
1275
99.75 percent pure aluminum with two control over individual impurities.
Wrought Aluminum
has exceptional mechanical properties and can be formed into various standard and nonstandard shapes.
-is when the metal is worked in the solid form with the help of specific tools.
Cast Aluminum
contains larger percentages of alloying elements when compared to wrought aluminum. It also has a generally lower tensile strength than rough aluminum due to the difficulty in eliminating casting defects. It is the resulting product created after molten aluminum is poured into a mold.
Titanium and titanium Alloy
has high structural strength which it retains to high temperature. It is used in turbine engines, and for aircraft skins in areas where the temperature is high.
A-B-C classification of titanium alloys
were established to provide a convenient and simple mean of describing all titanium alloys.
A(alpha), B(Beta), and C(combined alpha and beta)
Titanium and Titanium alloys possess three basic types of crystals.
A (Alpha)
all around performance; good weldability; tough and strong both cold and hot, and resistant to oxidation.
B (Beta)
bendability; excellent bend ductility; strong both cold and hot, but vulnerable to contamination.
C (combined alpha and beta for compromise performances)
Strong when cold and warm, but weak when hot; good bendability; moderate contamination resistance; excellent forgeability.