The History of Aircraft Materials
Instructor Notes
Introduction
These instructor notes contain commentary for each of the accompanying
slideshow presentation. These notes are followed with related student activities, a
test that may be administered before and/or after the module and references. Each
presentation slide is numbered in the lower left-hand corner to facilitate matching
the sequence with these notes. This material is intended to be delivered in two 50
minute classes if the pre/post test, presentation and activities are all used.
A suggested schedule:
Class 1:
Pre-test
Presentation
10 minutes
40 minutes
Class 2:
Review
Activities
Post-test
Slide 1
10 minutes
20 minutes
20 minutes
Title Slide - The History of Aircraft Materials
This presentation is a brief history of the development, use and adaptation of
materials to the construction of aircraft.
Slide 2
Questions to answer in this module…
What is the brief history of the materials used to construct aircraft?
Why were these materials adopted?
Why did some materials replace others?
What is the future for materials in aircraft?
Slide 3
1843 - Rubber
Mayans used rubber tree sap to make balls for games
Charles Goodyear added sulfur and heat to rubber to create a tough, durable form
that could be molded into shapes.
Rubber has become critical for the production of tires, seals and gaskets
Currently, many applications that used natural rubber have been replaced by
synthetic rubbers with high temperature, hardness or degradation resistance.
Rubber is an elastomer, meaning it can be made to stretch great lengths and return
to its original shape.
Images Shown: A tapped rubber tree, and typical pneumatic tire.
Slide 4
1903 - First Flight
The Wright Brothers made their first controlled self-propelled flight on December
17th, 1903 at Kill Devil Hills near Kitty Hawk North Carolina.
Many gliders been built previous.
The design featured:
An engine with a lightweight aluminum engine block
Spruce and steel wire structure
Fabric skin
Image Shown: The Wright Flyer at the National Smithsonian Museum of Flight.
Slide 5
1903 - Wright Brothers
Why wood and wire structure?
Wood is a natural composite material that has high strength to weight
ratio. It is easy to work with and shape with limited tools. It is tough
(resistant to damage) and flexible
Steel wire provided additional stiffening that could be adjusted and it was
thin in cross-section- so it would not add too much drag.
Why fabric skin?
The fabric was stretched over the spruce frame and coated with sealant.
This initial skin structure performed much like the sails of ships.
Slide 6
1903 - Aluminum Engine
The Wright Brother’s engine was a large part of their success in flight.
In 1903 aluminum was still a new material.
Aluminum was first produced in metal form in 1825,
but was not available commercially until electricity became plentiful because
large amounts of energy are required to refine it.
In 1903 most engines were constructed with cast iron which is roughly 3 times the
weight of aluminum per unit volume.
Many engines of the time were steam engines and did not have high horsepower
for their weight.
The Wright Brothers surveyed engine manufacturers of the time; none could
make an affordable, lightweight engine with enough power.
They decided to design and build their own using aluminum.
Image Shown: One of the early Wright Brothers engines.
Slide 7
1907 – Plastic
Plastics had been discovered prior to 1907, but Leo Hendrik Baekeland refined
plastic production to create a product called bakelite. This new plastic could be
molded into any shape and proved to be stronger and more durable than previous
types. Thus a new material type was available for control knobs, and electrically
insulating parts.
Image Shown: A bakelite engine distributor rotor.
Slide 8
1915 – All Metal Airplane
In 1915 Hugo Junkers built the first all metal airplane using a tubular structure
covered with corrugated sheet iron. This was a step away from the limitations of
using only natural wood materials with fixed properties.
Image Shown: An early Junkers airplane with iron sheet skin.
Slide 9
1916 - Stressed-Skin Construction
The LFG Roland C.II used formed plywood skin. Fabricated plywood uses the
natural composite of wood and tailors the properties by alternating the grain
direction and thickness.
This aircraft was different than all previous because the plywood skin became part
of the structure. No longer was the skin acting only as a sail to deflect the air, it
was holding the craft together.
Image Shown: The LFG Roland C.II stressed skin biplane.
Slide 10
Stressed-Skin Construction
Why stressed-skin?
The stressed skin concept combines the support structure and the aircrafts skin.
If the aircraft is built using a skeleton structure it would still require a skin for
aerodynamics, but if the skin is made stiff enough to resist tension and
compression, a skeleton structure is not required. If the correct design and
materials are chosen, a weight savings can be achieved.
Image Shown: Space frame construction fuselage that does not use stressed-skin.
Slide 11
1926 – Semi-Monocoque Construction
In 1925 Henry Ford purchased the Stout Metal Airplane Company. The aircraft
designed and built were based on the previous work of Junkers.
Ford Tri-motor employed stressed-skin construction also known as semimonocoque construction.
In semi-monocoque construction the skeletal structure is not replaced by a
structural skin, it is minimized. The skin does its aerodynamic task, carries
structural loads, and is reinforced with ribs and spars.
In full monocoque construction, the skeletal ribs, spars and stiffeners would be
eliminated- only a structural skin would be used.
Note that the Ford Tri-motor used a corrugated skin to increase its stiffness. It
was later determined that this surface roughness created much drag.
Image Shown: Ford Tri-motor aircraft.
Slide 12
Semi-Monocoque Construction
Semi-monocoque construction cutaway
Image Shown: Modern Boeing 747 shown but the concept has changed little
from first inception.
Sheet metal skin, riveted lamination sheet metal ribs and formed stringers all
riveted together.
Slide 13
1930’s – Increased Aluminum Use
Starting with the initial flight of the Wright Brothers, aluminum saw
increased use as it was produced cheaper and with better properties.
In the early 1930’s wood and wire construction was still competitive with early
aluminum construction.
By the late 1930’s aluminum construction techniques and semi-monocoque
construction supplanted wood structures.
Duralumin, an alloy of aluminum with copper added had been developed in 1903
by German metallurgist Alfred Wilm. The addition of copper allowed the
material to become stronger with age, but created corrosion problems especially
in salt water environments.
The United States Navy funded the development of Alclad- which consisted of
duralumin with pure aluminum coating to protect the alloy from corrosion.
Image Shown: Corroded aircraft components.
Slide 14
1931 – Stainless Steel Construction
In 1931 the Budd Company built the BB-1 Pioneer out of stainless steel sheet and
strip using newly developed spot welding technologies. The design was Italian in
origin and used sheet metal frame, sheet metal skinned fuselage and floats, and
fabric covers wings and control surfaces.
The Budd Company was the leader in building railcar which used large amounts
of stainless steel. The company viewed stainless steel aircraft as a way to expand
business and solve the corrosion issues associated with duralumin.
This aircraft was a flying boat configuration and performed as expected, logging
roughly 1000 flight hours.
Image Shown: The Budd BB-1 Pioneer on display outside the Franklin Institute
in Philadelphia.
Slide 15
Steel/ Stainless Steel vs. Aluminum
So why not build all aircraft out of stainless steel?
Stainless steel alloys generally have better corrosion resistance than aluminum
Aluminum is roughly 1/3 the weight of stainless steel
Stainless has been more costly
Thin stainless sheet is been susceptible to buckling failure than thicker aluminum
sheet of the same weight
For a simple beam structure under a bending load, the top surface of the beam in
loaded in compression, while the bottom surface is loaded in tension.
If the structure is changed to a tube, like a fuselage, the top skin is loaded in
compression and the bottom is in compression. If the skin is too thin, the top
surface in compression will buckle like an empty stepped on soda can.
Image Shown: A simple beam under loading, and a large sheet metal test sample
demonstrating buckling failure.
Slide 16
1936 - Plastics Use Expands
Plexiglas is a trade name patented in 1933 by German chemist Otto Röhm.
Sheets were made commercially available by 1936 and quickly adapted for
optical applications including aircraft windscreens and canopies.
The material is light, transparent, good impact resistance and is easily molded or
formed. It also weathers the environment well and will not yellow from UV
radiation.
This material assisted in allowing designers of aircraft to continue to create
enclosed, comfortable and eventually pressurized cockpits and cabins.
Image Shown: A modern Plexiglas aircraft canopy.
Slide 17
1942 – Composites - Fiberglass
Fiberglass was first produced by accident at Corning Glass by blowing air into
molten glass by researcher Dale Kleist. By the late 1930’s fiberglass was being
spun to create cloth. In 1941 it was discovered that heat treating the fibers gave
increased flexibility which is key to use in composites.
Early in World War II, British agents stole the secrets to making polyester resin
which was given to American manufacturing firms to use as matrix material to
hold the fiberglass together. By 1942 Owens-Corning was producing aircraft
cockpit components from the fiberglass polyester composite materials.
Aircraft noses are often constructed from fiberglass to house the radar systems
and allow radio frequency transmission.
Image Shown: Fiberglass cloth weave and a modern aircraft nose.
Slide 18
1940’s – 1950’s - Superalloys
Before World War II iron based alloys were developed for high temperature
work. The war increased demand of performance materials for turbochargers and
jets.
A superalloy is defined as a metal that has high strength and creep resistance at
high temperatures, in addition to corrosion resistance.
Superalloys are now cobalt, nickel or nickel-iron based and some are “grown” as
single crystals. A typical application is jet engine turbine blades.
Superalloys are known with such names as: Hastelloy, Inconel, Waspaloy, Rene
alloys and others.
Image Shown: Red hot superalloy forgings.
Slide 19
1950-1963 - Titanium
In 1950 the Titanium Metals Corporation of America was formed as a joint
venture of National Lead Company and Allegheny Ludlum Steel Corporation.
The National Lead Co. had been studying titanium for several years prior as a
replacement for stainless steel in some applications.
It was noted that the metal resisted corrosion, resisted acids and had high strength.
Titanium was identified as a strategic material for aircraft, 40% lighter than
stainless steel and a focal point for Cold War production.
Estimated weight savings per aircraft using titanium were 400 to 4,000 pounds
per engine depending on the size of the aircraft.
The Mach 3.2 capable A-12 and its replacement, the SR-71 were both largely
built from titanium to withstand the high temperatures generated at speed.
Image Shown: The A-12, the precursor to the SR-71.
Slide 20
1969 – Carbon Fiber Composites
Carbon fiber can be made to a tensile strength roughly 5 times that of steel.
It is typically used with epoxy resins or other plastic to form a matrix that keeps
the fibers together.
Rolls-Royce developed the RB211-06 engine for the Lockheed L-1011 airliner.
Rolls-Royce decided to use “Hyfil”, a newly developed carbon fiber from Royal
Aircraft Establishment at Farnborough for the fan stage.
This British patented process allowed Rolls-Royce to save a considerable amount
of weight giving the RB211 engine a higher power to weight ratio than
competitors engines.
Unfortunately the development costs for the new engine and materials in a
fiercely competitive market forced Rolls-Royce into bankruptcy and required a
government bailout.
Images Shown: The RB211 turbofan jet engine, and woven carbon fiber.
Slide 21
1970 – Boron Fiber Composites
Boron fibers were discovered to have higher strength than carbon fibers.
Unfortunately boron composites had three significant problems which limited it
use:



The boron had to be deposited on a tungsten wire substrate.
The processing was expensive.
Boron filaments cannot be bent into tight radii.
The F-14 jet fighter was the first aircraft produced with boron composites
included in the initial design
Image Shown: The F-14 “Tomcat” jet fighter.
Slide 22
1981 - Ceramics
The Space Shuttle uses thermal insulation made from 99.9% pure silica glass
fibers and 94% by volume air.
This light ceramic, with a density of 9 pounds per cubic foot allows the shuttle to
survive re-entry into the Earth’s atmosphere at Mach 25.
The material is called LI-900 and is manufactured by Lockheed into tiles which
are glued onto the Shuttle.
A LI-900 tile minimizes thermal conductivity while providing maximum thermal
shock resistance to the point that it can be heated to 2200°F and immediately
plunged into cold water without damage.
Image Shown: The Space Shuttle in simulated re-entry to Earth’s atmosphere.
Slide 23
1998 – Aluminum- Lithium
Aluminum-lithium is an advanced alloy with trace amounts of copper, zinc,
manganese, magnesium, zirconium and iron which first saw limited aerospace use
in the 1950’s.
Lithium is the worlds lightest metal, and its addition to aluminum, decreases
weight, improves strength, toughness, corrosion resistance, and formability.
The Space Shuttle external fuel tank was changed to aluminum lithium alloy in
1998 bringing its weight from 66,000 lbs. to 58,800 to increase payload capacity.
The new Airbus A350 uses a considerable amount of aluminum-lithium for the
wings and fuselage, this amount is reported to be as high as 20%.
Another important characteristic of Al-Li alloys is their superior Fatigue Crack
Growth (FCG) performance. This allows the use of less material and weight for
equal safety margins when compared to other advanced materials such as
composites. Al-Li is a good choice for structures that must be damage tolerant.
Image Shown: The Space Shuttle launching, the large center tank is the external
fuel tank.
Slide 24
2005 - GLARE
“GLAss-REinforced” Fiber Metal Laminate (FML)
GLARE is a composite laminate construction of alternating layers of thin
aluminum and layers of fiber glass and plastic matrix material. The fiber
orientation of the fiberglass can be tailored to produce desired strength and
stiffness.
Although GLARE is a composite material, it can be processed for component
fabrication much like aluminum sheet. It exhibits less similarity to traditional
composites that are more complex for design, manufacture, inspection and
maintenance.
Advantages over conventional aluminum construction are:




Superior damage tolerance to impact and fatigue
Better corrosion resistance
Better fire resistance
Lower specific weight
Image Shown: The Airbus A380 airliner uses GLARE composites.
Slide 25
2009 – Boeing 787 Dreamliner
Large scale composite use:
The Boeing 787 weight breakdown by material type:
50% composite
20% aluminum
15% titanium
10% steel
5% other
(fuselage, wings, tail, doors and interior)
(wing and tail leading edges)
(engines components)
(various locations)
The plane will be 80% composite by volume.
This ends up being 35 tons per aircraft of carbon fiber and plastic composite of
which 23 tons is carbon fiber.
This widespread use of composites will make the 787 nearly 20% more efficient
than the earlier 767 of similar size and role.
Image Shown: A Boeing 787 carbon fiber fuselage section.
Slide 26
Future- Intelligent materials
Imbedded sensors:
Stress/Strain
Impact/Damage
Heat
Computer material health monitoring and real conditions maintenanceThe system determines when maintenance and repair are needed.
Materials change properties and configurations
Image Shown: NASA Biomechanical Aerial Technology System (BATS)
Slide 27
Future- Nanotechnology
Ultra-strength composites by accurately building molecular structures
Locally tailored materials for specific requirements
The properties of the material can vary by location such as:
Density
Strength
Flexibility
Heat or electrical conduction
Image Shown: Carbon nanotubes
Slide 28
Summary-
What is the brief history of the materials used to construct aircraft?
Natural composites (wood, fabric) 
Aluminum 
Synthetic composites (fiberglass, carbon fiber)
Why were these materials adopted?
For a number of reasons:
Higher strength to weight ratios
Better corrosion resistance
Better fatigue resistance
Lower overall cost (for performance, processing, manufacturing…)
Better thermal properties (for high temperatures at higher speeds)
What is the future for materials in aircraft?
Increased composites use and development
Intelligent materials and nanotechnology
Student Activities:
Group Activity:
Break into groups of three, and each group choose a specific material used
to manufacture aircraft. Create a five minute presentation addressing the
following points:
 How is this material processed from raw materials?
 How much of this material is used each year for aircraft?
 What is the future trend for this material in aircraft manufacturing
 What kind of aircraft components is this material used for?
 What are the material properties?
 What kind of equipment is needed to produce parts from this material?
Individual Activities:
1.
Write a one page paper that explains in detail why one material
used for aircraft was replaced by another material.




2.
What were the costs?
Where the choices strategic?
Was there a downside to this change?
What was the driving factor?
Research and list some of the required fluids for aircraft
manufacturing and operation.
Pre/Post Test:
1. What kind of composite materials were used for the first aircraft?
a.
b.
c.
d.
Carbon fiber
Aluminum
Natural composites
Titanium
2. Why was aluminum important to the Wright’s flyer succeeding?
a.
b.
c.
d.
It allowed the fabrication of the wings
It was lighter than a cast iron engine
Aluminum tubing was used
It wasn’t important
3. What material was deemed a strategic resource for aircraft during the Cold
War?
a.
b.
c.
d.
Copper
Aluminum
Steel
Titanium
4. In a monocoque structure the stresses are carried by the…
a.
b.
c.
d.
Skin
Stringers
Ribs
All of the above
5. Carbon fiber has a strength that is roughly _______ that of the same size piece
of steel.
a.
b.
c.
d.
Twice
Half
Same
Five times
6. Boron fiber composites are very high strength, but what is one reason they
have not seen widespread use?
7. What is the material most used for transparent canopies?
a.
b.
c.
d.
Lexan
Aluminum
Carbon fiber
Plexiglas
8. The Space Shuttle external fuel tank structure was originally made from
aluminum, what material was it redesigned for to increase the Shuttle’s
payload capacity?
9. Name two emerging technologies that will see increased use for future
aircraft.
10. What component of composites was accidentally discovered in the 1930’s and
saw expanded use in a minor role during World War II?
11. List three reasons for the development of newer materials for aircraft.
12. What was the problem encountered with the use of early aluminum alloys?
13. Why didn’t the use of stainless steel for aircraft structures gain widespread use
as shown by the Budd Company?
14. What material is tapped from trees in its raw form to make fluid seals?
15. The Boeing 787 airliner uses a majority of _________ to create a new level of
fuel efficiency.
a.
b.
c.
d.
Aluminum
Carbon fiber
GLARE
Boron composite
References:
Aluminum construction
http://www.centennialofflight.gov/essay/Aerospace/Junkers/Aero55.htm
http://en.wikipedia.org/wiki/Aluminum
http://en.wikipedia.org/wiki/Duralumin
Aluminum – Lithium
http://aluminumlithium.com/
http://www.wired.com/wiredscience/2007/11/my-what-a-big-o/
Boron composites
http://www.anft.net/f-14/f14-history-f14a-interavia.htm
http://en.wikipedia.org/wiki/F14_Tomcat
Carbon fiber- Rolls Royce RB211
http://en.wikipedia.org/wiki/Rolls-Royce_RB211
Composites
http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/materials/public/
composites/Composites_Overview.htm
Ceramics
http://en.wikipedia.org/wiki/Space_Shuttle
http://en.wikipedia.org/wiki/LI-900
Fiberglass
http://en.allexperts.com/e/h/hi/history_of_fiberglass.htm
Glare
http://en.wikipedia.org/wiki/Glare_(material)
http://en.wikipedia.org/wiki/Airbus_A380
Intelligent materials
http://www.morpheus.umd.edu/research/systems/BATS.html
Plastics
http://www.mindfully.org/Plastic/Plastics-History.htm
http://inventors.about.com/od/pstartinventions/a/plastics.htm
http://www.statemaster.com/encyclopedia/Bakelite
http://en.wikipedia.org/wiki/Poly(methyl_methacrylate)
Semi-monocoque and monocoque construction
http://en.wikipedia.org/wiki/Monocoque
http://www.centennialofflight.gov/essay/Evolution_of_Technology/metal_
plane/Tech15.htm
http://en.wikipedia.org/wiki/Fuselage
http://www.tpub.com/content/aviation/14014/css/14014_78.htm\
Stainless steel construction
http://en.wikipedia.org/wiki/Budd_BB-1_Pioneer
Superalloys
http://www.tms.org/Meetings/Specialty/Superalloys2000/SuperalloysHisto
ry.html
http://en.wikipedia.org/wiki/Superalloy
http://www.eramet.fr/us/Site/Template/T1.aspx?SELECTID=122&ID=10
9
Titanium
http://www.fundinguniverse.com/company-histories/Titanium-MetalsCorporation-Company-History.html
http://www.californiasciencecenter.org/Exhibits/AirAndSpace/AirAndAir
craft/A12/A12.php
http://www.sr-71.org/blackbird/a-12/
Wright Brothers
http://en.wikipedia.org/wiki/Wright_brothers