aircraft materials history

8/10/2019 Aircraft Materials History

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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. achpresentation slide is numbered in the lower left!hand corner to facilitate matching

the se"uence with these notes. This material is intended to be delivered in two #$

minute classes if the pre/post test, presentation and activities are all used.

A suggested schedule%

&lass '%

(re!test '$ minutes

(resentation )$ minutes

&lass *%

+eview '$ minutesActivities *$ minutes

(ost!test *$ minutes

lide ' Title lide ! The History of Aircraft Materials

This presentation is a brief history of the development, use and adaptation ofmaterials to the construction of aircraft.

lide * -uestions to answer in this module

hat is the brief history of the materials used to construct aircraft0

hy were these materials adopted0

hy did some materials replace others0

hat is the future for materials in aircraft0


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lide 1 '2)1 ! +ubber

Mayans used rubber tree sap to ma3e balls for games

&harles 4oodyear added sulfur and heat to rubber to create a tough, durable form

that could be molded into shapes.

+ubber has become critical for the production of tires, seals and gas3ets

&urrently, many applications that used natural rubber have been replaced by

synthetic rubbers with high temperature, hardness or degradation resistance.

+ubber is an elastomer, meaning it can be made to stretch great lengths and return

to its original shape.

Images hown% A tapped rubber tree, and typical pneumatic tire.

lide ) '5$1 ! 6irst 6light

The right 7rothers made their first controlled self!propelled flight on 8ecember

'9th, '5$1 at :ill 8evil Hills near :itty Haw3 North &arolina.

Many gliders been built previous.

The design featured%

An engine with a lightweight aluminum engine bloc3

pruce and steel wire structure6abric s3in

Image hown% The right 6lyer at the National mithsonian Museum of 6light.

lide # '5$1 ! right 7rothers

hy wood and wire structure0

ood is a natural composite material that has high strength to weight

ratio. It is easy to wor3 with and shape with limited tools. It is tough

;resistant to damage< and fle=ibleteel wire provided additional stiffening that could be ad>usted and it was

thin in cross!section! so it would not add too much drag.

hy fabric s3in0

The fabric was stretched over the spruce frame and coated with sealant.This initial s3in structure performed much li3e the sails of ships.


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This aircraft was different than all previous because the plywood s3in became part

of the structure. No longer was the s3in acting only as a sail to deflect the air, it

was holding the craft together.

Image hown% The D64 +oland &.II stressed s3in biplane.

lide '$ tressed!3in &onstruction

hy stressed!s3in0

The stressed s3in concept combines the support structure and the aircrafts s3in.

If the aircraft is built using a s3eleton structure it would still re"uire a s3in foraerodynamics, but if the s3in is made stiff enough to resist tension and

compression, a s3eleton structure is not re"uired. If the correct design and

materials are chosen, a weight savings can be achieved.

Image hown% pace frame construction fuselage that does not use stressed!s3in.

lide '' '5*? C emi!Monoco"ue &onstruction

In '5*# Henry 6ord purchased the tout Metal Airplane &ompany. The aircraft

designed and built were based on the previous wor3 of Eun3ers.

6ord Tri!motor employed stressed!s3in construction also 3nown as semi!

monoco"ue construction.

In semi!monoco"ue construction the s3eletal structure is not replaced by a

structural s3in, it is minimiFed. The s3in does its aerodynamic tas3, carriesstructural loads, and is reinforced with ribs and spars.

In full monoco"ue construction, the s3eletal ribs, spars and stiffeners would be

eliminated! only a structural s3in would be used.

Note that the 6ord Tri!motor used a corrugated s3in to increase its stiffness. It

was later determined that this surface roughness created much drag.

Image hown% 6ord Tri!motor aircraft.

lide '* emi!Monoco"ue &onstruction

emi!monoco"ue construction cutaway

Image hown% Modern 7oeing 9)9 shown but the concept has changed little

from first inception.


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heet metal s3in, riveted lamination sheet metal ribs and formed stringers all

riveted together.

lide '1 '51$@s C Increased Aluminum Gse

tarting with the initial flight of the right 7rothers, aluminum sawincreased use as it was produced cheaper and with better properties.

In the early '51$@s wood and wire construction was still competitive with earlyaluminum construction.

7y the late '51$@s aluminum construction techni"ues and semi!monoco"ueconstruction supplanted wood structures.

8uralumin, an alloy of aluminum with copper added had been developed in '5$1by 4erman metallurgist Alfred ilm. The addition of copper allowed the

material to become stronger with age, but created corrosion problems especiallyin salt water environments.

The Gnited tates Navy funded the development of Alclad! which consisted of

duralumin with pure aluminum coating to protect the alloy from corrosion.

Image hown% &orroded aircraft components.

lide ') '51' C tainless teel &onstruction

In '51' the 7udd &ompany built the 77!' (ioneer out of stainless steel sheet and

strip using newly developed spot welding technologies. The design was Italian inorigin and used sheet metal frame, sheet metal s3inned fuselage and floats, and

fabric covers wings and control surfaces.

The 7udd &ompany was the leader in building railcar which used large amountsof stainless steel. The company viewed stainless steel aircraft as a way to e=pand

business and solve the corrosion issues associated with duralumin.

This aircraft was a flying boat configuration and performed as e=pected, logging

roughly '$$$ flight hours.

Image hown% The 7udd 77!' (ioneer on display outside the 6ran3lin Institutein (hiladelphia.


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lide '# teel/ tainless teel vs. Aluminum

o why not build all aircraft out of stainless steel0

tainless steel alloys generally have better corrosion resistance than aluminum

Aluminum is roughly '/1 the weight of stainless steeltainless has been more costly

Thin stainless sheet is been susceptible to buc3ling failure than thic3er aluminum

sheet of the same weight

6or 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, li3e a fuselage, the top s3in is loaded in

compression and the bottom is in compression. If the s3in is too thin, the topsurface in compression will buc3le li3e an empty stepped on soda can.

Image hown% A simple beam under loading, and a large sheet metal test sample

demonstrating buc3ling failure.

lide '? '51? ! (lastics Gse =pands

(le=iglas is a trade name patented in '511 by 4erman chemist Btto +hm.

heets were made commercially available by '51? and "uic3ly adapted foroptical applications including aircraft windscreens and canopies.

The material is light, transparent, good impact resistance and is easily molded orformed. It also weathers the environment well and will not yellow from G

radiation.

This material assisted in allowing designers of aircraft to continue to createenclosed, comfortable and eventually pressuriFed coc3pits and cabins.

Image hown% A modern (le=iglas aircraft canopy.

lide '9 '5)* C &omposites ! 6iberglass

6iberglass was first produced by accident at &orning 4lass by blowing air into

molten glass by researcher 8ale :leist. 7y the late '51$@s fiberglass was being

spun to create cloth. In '5)' it was discovered that heat treating the fibers gaveincreased fle=ibility which is 3ey to use in composites.


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arly in orld ar II, 7ritish agents stole the secrets to ma3ing polyester resin

which was given to American manufacturing firms to use as matri= material to

hold the fiberglass together. 7y '5)* Bwens!&orning was producing aircraftcoc3pit components from the fiberglass polyester composite materials.

Aircraft noses are often constructed from fiberglass to house the radar systemsand allow radio fre"uency transmission.

Image hown% 6iberglass cloth weave and a modern aircraft nose.

lide '2 '5)$@s C '5#$@s ! uperalloys

7efore orld ar II iron based alloys were developed for high temperature

wor3. The war increased demand of performance materials for turbochargers and

>ets.

A superalloy is defined as a metal that has high strength and creep resistance athigh temperatures, in addition to corrosion resistance.

uperalloys are now cobalt, nic3el or nic3el!iron based and some are JgrownK as

single crystals. A typical application is >et engine turbine blades.

uperalloys are 3nown with such names as% Hastelloy, Inconel, aspaloy, +ene

alloys and others.

Image hown% +ed hot superalloy forgings.

lide '5 '5#$!'5?1 ! Titanium

In '5#$ the Titanium Metals &orporation of America was formed as a >oint

venture of National Dead &ompany and Allegheny Dudlum teel &orporation.

The National Dead &o. 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, )$L lighter than

stainless steel and a focal point for &old ar production.stimated weight savings per aircraft using titanium were )$$ to ),$$$ pounds

per engine depending on the siFe of the aircraft.

The Mach 1.* capable A!'* and its replacement, the +!9' were both largely

built from titanium to withstand the high temperatures generated at speed.

Image hown% The A!'*, the precursor to the +!9'.


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The material is called DI!5$$ and is manufactured by Doc3heed into tiles which

are glued onto the huttle.

A DI!5$$ tile minimiFes thermal conductivity while providing ma=imum thermal

shoc3 resistance to the point that it can be heated to **$$6 and immediatelyplunged into cold water without damage.

Image hown% The pace huttle in simulated re!entry to arth@s atmosphere.

lide *1 '552 C Aluminum! Dithium

Aluminum!lithium is an advanced alloy with trace amounts of copper, Finc,

manganese, magnesium, Firconium and iron which first saw limited aerospace use

in the '5#$@s.

Dithium is the worlds lightest metal, and its addition to aluminum, decreasesweight, improves strength, toughness, corrosion resistance, and formability.

The pace huttle e=ternal fuel tan3 was changed to aluminum lithium alloy in

'552 bringing its weight from ??,$$$ lbs. to #2,2$$ to increase payload capacity.

The new Airbus A1#$ uses a considerable amount of aluminum!lithium for the

wings and fuselage, this amount is reported to be as high as *$L.

Another important characteristic of Al!Di alloys is their superior 6atigue &rac3

4rowth ;6&4< performance. This allows the use of less material and weight for

e"ual safety margins when compared to other advanced materials such ascomposites. Al!Di is a good choice for structures that must be damage tolerant.

Image hown% The pace huttle launching, the large center tan3 is the e=ternal

fuel tan3.

lide *) *$$# ! 4DA+

J4DAss!+inforcedK 6iber Metal Daminate ;6MD

aircraft materials history

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