1. AIRCRAFT MATERIALS
Review of the Course
AIRCRAFT MATERIALS

2. AIRCRAFT MATERIALS
1. Basic requirements
• High strength and stiffness
• Low density
=> high specific properties e.g. strength/density, yield strength/density,
E/density
• High corrossion resistance
• Fatigue resistance and damage tolerance
• Good technology properties (formability, machinability, weldability)
• Special aerospace standards and specifications
2. Basic aircraft materials for airframe structures
• Aluminium alloys
• Magnesium alloys
• Titanium alloys
• Composite materials

3. Development of aircraft materials for airframe structures
composites
Mg alloys
other Al alloys
pure AlZnMgCu
alloys
pure AlCuMg
alloys
new Al
alloys
steel
Year
AlCuMg alloys
wood
other materials
Relative share
of structural
materials Ti alloys

4. Structural materials on small transport aeroplane

5. Development of composite
aerospace applications over the last 40 years

6. Composite share in military aircraft structures in USA and
Europe
Structural materials on Eurofighter

7. Structural materials on Eurocopter

8. Comparison of mechanical performance of composite
materials and light metals

9. Aluminium Alloys

10. Aluminium – Al
• plane centered cubic lattice
• melting point 660 °C
• density 2.7 g/cm³
• very good electrical and heat conductivity
• very good corrosion resistance
• low mechanical properties
• solid solutions with alloying elements
• maximum solubility is temperature dependent
– Cu: 6 % at 548 °C; 0.1 % at RT
– Mg: 17 % at 449 °C; 1.9 % at RT
– Zn: 37 % at 300 °C; 2 % at RT
– Si: 1.95 % at 577 °C; 0 % at RT
Substitution solid solution
a) alloying atom > aluminium atom
b) pure aluminium
c) alloying atom < aluminium atom

11. Characteristics of aluminium alloys
Advantages
• Low density 2.47- 2.89 g/cm³
• Good specific properties – Rm/ρ, E/ ρ
• Generally very good corrosion
resistance (exception alloys with
Cu)
• Mostly good weldability – mainly
using pressure methods
• Good machinability
• Good formability
• Great range of semifinished
products
(sheet, rods, tubes etc.)
• Long-lasting experience
• Acceptable price
Shortcomings
• Low hardness, susceptibility to
surface damage
• High strength alloys (containing Cu)
need additional anti-corrosion
protection:
– Cladding – surface protection using
a thin layer of pure aluminium or
alloy with the good corrosion
resistance
– Anodizing – forming of surface oxide
layer (Al2O3)
• It is difficult to weld high strength
alloys by fusion welding
• Danger of electrochemical corrosion
due to contact with metals:
– Al-Cu, Al-Ni alloys, Al-Mg alloys, Al-
steel

12. Designation of aluminium alloys according to EN
Wrought alloys
AL-PXXXX(A)
designation basic alloying element
• 1XXX – pure aluminium
• 2XXX - copper (Cu)
• 3XXX - manganese (Mn)
• 4XXX - silicon (Si)
• 5XXX - magnesium (Mg)
• 6XXX - Mg + Si
• 7XXX - zinc (Zn)
• 8XXX - other (eg. Li)
Casting alloys
AL-CXXXXX
designation basic alloying element
• 1XXXX - > 99.0 % Al
• 2XXXX - Cu
• 3XXXX - Si-Mg
- Si-Cu
- Si-Cu-Mg
• 4XXXX - Si
• 5XXXX - Mg
• 7XXXX - Zn
• 8XXXX - Sn

13. Important wrought aluminium alloys for aircraft structures
• 2XXX (Al-Cu, Al-Cu-Mg) - high strength, lower corrosion resistance
2014 (0.8Si, 4.4Cu, 0.8Mn, 0.5Mg)
2017 (0.5Si, 4Cu, 0.7Mn, 0.6Mg)
2024 (4.4Cu, 0.6Mn, 1.5Mg)
2024Alclad (with the surface layer of Al)
2027 (4.4Cu, 0.9Mn, 1.3Mg, 0.2Zn, 0.05Cr, 0.25Ti)
2124 (4.4Cu, 0.6Mn, 1.5Mg, 0.1V)
2219 (6.3Cu, 0.3Mn, 0.1V)
• 6XXX (Al-Mg-Si) -comparing to 2XXX - lower strength, better ductility
and corrosion resistance
6013 (0.8Si, 0.8Cu, 0.50Mn, 1.0Mg)
6061 (0.6Si, 0.28Mn, 1.0Mg, 0.2Cr)
6061Alclad
6056 (1.0Si, 0.9Mg, 0.8Cu, 0.7Mn, 0.25Cr, 0.2Ti+Zr)
• 7XXX (Al-Zn-Mg-Cu) – the highest strength, lower ductility, notch
sensitivity
7050 (2.3Cu, 2.2Mg, 0.12Zr, 6.2Zn)
7075 (1.6Cu, 2.5Mg, 0.13Cr, 5.6Zn), 7075Alclad
7175 (1.6Cu, 2.5Mg, 0.23Cr, 5.6Zn)
7475 (1.6Cu, 2.2Mg, 0.22Cr, 5.7Zn)

14. Most important tempers aluminium alloys
• O - anealing
• W - solution treating + quenching (non stabil state)
• H - strain-hardening (strength is increased only due to cold working)
• T3 - solution treating + quenching + cold working + room
temperature aging
• T351- solution treating + quenching + stress relief due to controlled
stretching + room temperature aging
• T4 - solution treating + quenching + room temperature aging
• T6 - solution treating + quenching + artificial aging
• T651- solution treating + quenching + stress relief due to controlled streching +
artificial aging
• T7 - solution treating + quenching + artificial overaging
• T73 - solution treating + quenching + artificial overaging for the best stress
corrosion resistance
• T8 - solution treating + quenching + cold working + artificial aging

15. Reference aluminium alloys in airframe structure
Structure Part Control parametr Reference alloys
Wing Upper panels
Upper stringers
Lower panels
Lower stringers
Beams, ribs
compression
compression
damage tolerance (DT)
tension + DT
static properties
7150-T6/T77
7050-T74
2024-T3, 2324-T39
2024-T3
7050-T74, 7010-T76
Fuselage Upper panels
Lower panels
Stiffeners
Main frame
compression, DT, formability
tension + DT
tension/compression
complex
2024 clad-T3
2024 clad-T3
7175-T73
7010+7050-T74
Other
parts
All types 7010/7050/7075

16. Typical mechanical properties of alloy 2014
4.4Cu-0.8Si-0.8Mn-0.5Mg , E = 72.4 GPa , ρ = 2 .77 g/ccm
Temper Tensile strength
MPa
Yield strength
MPa
Elongation
%
Fatigue strength
MPa
At 500 mil. cycles
Bare sheet 2014
0 186 97 18 90
T4 427 290 20 140
T6 483 414 13 125
Alclad sheet 2014
0 172 69 21 -
T3 434 273 20 -

17. Typical mechanical properties of alloy 2024
4.4Cu-1.5Mg-0.6Mn, E = 72.4 GPa , ρ = 2 .77 g/ccm
Temper Tensile strength
MPa
Yield strength
MPa
Elongation
%
Fatigue strength
MPa
At 500 mil. cycles
Bare 2024
0 185 75 20 90
T3 485 345 18 140
T4, T351 470 325 20 140
Alclad 2024
0 180 75 20 -
T3 450 310 18 -
T4, T351 440 290 19 -

18. Typical mechanical properties of alloy 2124
4.4Cu-1.5Mg-0.6Mn, E = 72.4 GPa , ρ = 2 .77 g/ccm
Temper Tensile strength
MPa
Yield strength
MPa
Elongation
%
Fatigue strength
MPa
At 500 mil. cycles
Plate 2124 - L
T851 490 440 9 -
Plate 2124 - LT
T851 490 435 9 -
Plate 2124 - ST
T851 470 420 5 -
Better transvers properties, good strengths and creep resistance at higher temperatures -
for application between 120 – 175 °C.

19. Typical mechanical properties of alloy 6061
1.0Mg-0.6Si-0.3Cu-0.2Cr ; E = 68.9 GPa; ρ = 2 .70 g/ccm
Temper Tensile strength
MPa
Yield strength
MPa
Elongation
%
Fatigue strength
MPa
At 500 mil cycles
Bare 6061
0 124 55 25 62
T4 241 145 22 97
T6 310 276 12 97
Alclad 6061
0 117 48 25 -
T4 228 131 22 -

20. Minimal mechanical properties of alloy 6056
1.0Si-0.9Mg-0.8Cu-0.7Mn-0.25Cr-0.2Ti+Zr; ρ = 2 .72 g/ccm
Temper Tensile strength
MPa
Yield strength
MPa
Elongation
%
Fatigue strength
MPa
At 500 mil cycles
Thin extrusions - L
T4511 355 245 16 -
T6511 380 360 10 -
T78511 360 335 10 -
Bare sheet - LT
T4 265 135 18 -
T78 340 315 8 -

21. Mechanical properties of alloy 7050
6.22Zn-2.3Mg-2.3Cu-0.12Zr; E = 70.3 GPa; ρ = 2 .83 g/ccm
Direction Tensile strength
MPa
Yield strength
MPa
Elongation
%
Fatigue strength
MPa
At 10 mil. cycles
Minimum properties - Die forgings T-736 (T-74), thickness up to 50 mm
L 496 427 7 -
L-T 469 386 5 -
Minimum properties – Hand forgings T73652, thickness up to 50 mm
L 496 434 - -
L-T 490 421 - -
Typical properties – Plate T73651
L 510 455 11 170-300
Typical properties – Forgings T73652
L 524 455 15 210-275

22. Typical mechanical properties of alloy 7075
5.6Zn-2.5Mg-1.6Cu-0.23Cr; E = 71.0 GPa; ρ = 2 .80 g/ccm
Temper Tensile strength
MPa
Yield strength
MPa
Elongation
%
Fatigue strength
MPa
At 500 mil. cycles
Bare 7075
0 228 103 17 -
T6, T651 572 503 11 159
T73 503 434 - 159
Alclad 7075
0 221 97 17 -
T6, T651 524 462 11 -

23. Use of aluminum-lithium alloys in commercial aircraft

24. Typical mechanical properties of aluminium- lithium alloys
Temper Direction Tensile strength
MPa
Yield strength
MPa
Elongation
%
Alloy 2090: 2.7Cu-2.2Li-0.12Zr; E = 76 GPa, ρ = 2.59 g/ccm
T 83
(near peak aged)
L 530 527 3
LT 505 503 6
45° 440 440
Alloy 8090: 2.45Li-1.3Cu-0.95Mg-0.12Zr; E = 77 GPa; ρ = 2.55 g/ccm
T8X
(near peak aged)
L 480 400 4.5
LT 465 395 5.5
45° 400 325 7.5

25. Casting aluminum alloys
• Designation (in addition to EN)
– Often used system (Aluminum Association - USA): three digit designation
- the first digit indicates a main alloying element
• 1XX  99,0 % Al
• 2XX Al - Cu
• 3XX Al - Si - Mg
Al - Si - Cu
Al - Si - Cu - Mg
• 4XX Al - Si
• 5XX Al – Mg
• 7XX Al - Zn
• 8XX Al – Sn
A letter ahead of designation marks alloys with the same content of main
alloying elements but with different content of impurities or micro alloying
elements.(e.g. 201 - A201, 356 - A356, 357 - A357)
Additional digit .0 means shape casting, digit .1 or .2 ingots

26. • Typical castings in aircraft structures
Al – front body of engine
32 kg - D=700 mm
Al- steering part - 1,1 kg
390 x 180 x 100 mm
Al – pedal - 0,4 kg
180 x 150 x 100 mm
Al – casing - 1,3 kg
470 x 190 x 170 mm

27. • General characteristics
– Micro and macro structures of metal are influenced by conditions of metal
solidification – quantity of nuclei, temperature interval of solidification,
cooling rate …
A fine, equiaxed grain structure is normally desired in aluminum
casting (Al-Ti or Al-Ti-B alloys are most widely used grain refiners)
– Mechanical properties are influenced by existence of casting defects –
porosity, inclusions (mainly oxides), shrinkage voids ….
– Alloys – heat treatable , non heat treatable
– Mechanical properties are mostly lower comparing wrought alloys of the
similar chemical composition
– High quality aircraft casting need careful metallurgical processing of liquid
metal
• Degassing – hydrogen elimination (hydrogen causes porosity)
• Grain refinement and modification for better mechanical properties
• Filtration for inclusions removing

28. Alloy Al-7Si – the effect
of grain refinement
Solubility of hydrogen in
aluminum
During solidification - dissolved
hydrogen can precipitate and form
voids.

29. Dendritic microstructure of hypoeutectic alloy
AlSi10Mg – sand casting
wall thickness 2 mm wall thickness 10 mm
There is direct relation between mechanical properties and dendrite
arm spacing (DAS) → different properties in different portions of
casting

30. • Alloys of Al–Cu system
- Composition 4 – 6 % Cu
- Copper substantially improves strength and hardness in the as-cast and
heat- treated conditions
- Copper generally reduces corrosion resistance and, in specific compositions
stress corrosion susceptibility
- Copper also reduces hot tear resistance and decreases castability
- Main advantage: high strength up to 300 °C
- Basic alloys
• ČSN 424351, 201, A 201, AL 7
• 242, A242
• B295
- Application:
Smaller , simple, high-strength castings for service at higher
temperatures (cylinder heads, pistons, pumps, aerospace housings, aircraft
fittings)

31. • Alloys of Al–Si + (Mg, Cu, Ni) system
– The most important alloys for aircraft castings
– Silicon improves casting characteristics (fluidity, hot tear resistance, feeding),
Si content depends on casting methods
• Sand and plaster molds, investment casting 5-7% Si
• Permanent molds 7-9% Si
• Die casting 8-12% Si
– Alloys containing Mg are heat treatable, hardening phase is Mg2Si
– Alloys Al-Si with alloying elements Mg and Cu have after heat treatment high
mechanical properties but lower plasticity and corrosion resistance
– Ni is alloying element in hypereutectic alloys for service at higher temperatures (e.g.
engine pistons)
– Strength and ductility can be improved using modification for refinement of eutectic
phases
• Principal – addition small quantities of Na or Sr into liquid metal before casting
• Results – increased tensile strength (40 %), impact strength (up to 400 %), ductility (2x)
– Mechanical properties can be improved also due to grain refinement buy rapid cooling
in permanent metal molds

32. Representative aluminum alloys – sand casting
Alloy Temper
Mechanical properties
Rm
MPa
Rp0,2
MPa
HB A
%
A 201.0
AlCu4,5Ag0,7Mg0,25Mn0,3
T7 496 448 - 6
A 356.0
AlSi7Mg0,35
F
T6
T61*
159
278
283
83
207
207
-
75
90
6
6
10
A 357.0
AlSi7Mg0,55ZnBe0,05
T6
T6*
317
359
248
290
85
100
3
5
* permanent mold casting
F as cast
.0 shape casting

33. Magnesium Alloys

34. General characteristics of Mg alloys
• Pure magnesium
– Hexagonal crystal lattice
– ρ=1,74 g/cm³ , Rm=190 MPa, Rp0,2=95 MPa
– Used in metallurgy (alloying element in Al alloys, titanium metallurgy, ductile iron
metallurgy).
– Not used for structural purposes – magnesium alloys have better utility values
• Advantages of Mg alloys
– Low density (ρ = 1,76–1,99 g/cm³ ) → high specific strength (Rm/ ρ)
– Comparing Al alloys, lower rate of strength decrease in relation with temperature
– Lower notch sensitivity and higher specific strength at vibrating loads
– High damping capacity (influence of low modulus of elasticity ~47GPa)
– High specific bending stiffness (higher to 50 % comparing steel, to 20 % comparing Al)
→ high resistance against buckling
– High specific heat → minor temperature increasing at short time heating
– Very good machinability
– Applicability – most alloys up to 150 °C, some of them up to 350 °C.

35. • Shortcomings of Mg alloys
– High reactivity at increased temperatures
• Above 450 °C rapid oxidation, above 620 °C ignition (fine chips, powder)
• Melting and casting – protection against oxidation (chlorides, fluorides, oxides Mg,
powder sulfur, gases SO2, CO2).
– Lower corrosion resistance , generally difficult anti-corrosion protection
• Corrosion environment (air, sea water), impurities Fe, Cu, Ni forming intermetallic
compounds
• Electrochemical corrosion – in contact with the most of metals (Al alloys, Cu alloys, Ni
alloys, steel)
– Low formability at room temperature - most alloys cannot be formed without heating
– After forming – high strength anisotropy along and crosswise deformation –→
differences 20 to 30 %.
– Low shear strength and notch impact strength
– Low wear resistance
– Low diffusion rate during heat treatment → longtime processes , artificial aging is
necessary at precipitation hardening
– Relatively difficult joining – possible electrochemical corrosion, limited weldability
(hot cracking, weld porosity, possible welding techniques - inert gas welding, spot
welding)

36. • Designation according to EN 2032-1
– Wrought alloys MG-PXXXXX
– Casting alloys MG-CXXXXX
– In numerical designation, one or two digits represent one or two main alloying
elements according to their weight percentage. The third digit is zero, the last
two digits represent serial number.
(1- Al, 2 – Si, 3 – Zr, 4 – Ag, 5 – Th, 6 – rare earth, 7 – Y, 8 – Zn, 9 - other)
• More common designation - according to ASM:
– Series AZ (alloying elements Al, Zn)
– Series AM (Al, Mn)
– Series QE (Ag, RE - rare earth )
– Series ZK (Zn, Zr)
– Series AE (Al, RE)
– Series WE (Y, RE)
– Series HM, HZ, HK (Th, Mn, Zn, Zr) – high temperature alloys
– Two first digits – percentage of alloying elements
Designation of Mg alloys

37. Basic wrought Mg alloys
• Mg-Al-Zn (AZ)alloys
– The most common alloys in aircraft industry, applicable up to 150 °C
– Composition – 3 to 9 % Al, 0.2 to 1.5 % Zn, 0.15 to 0.5 % Mn
– Increasing Al content → strength improvement , but growth of susceptibility
to stress corrosion
– Zn → ductility improvement
– (Cd + Ag) as Zn replacement → high strength up to 430 MPa
– Precipitation hardening → strength improvement + decrease of ductility
– The most common alloy for sheet and plates – AZ31B (applicable to 100 °C)
Alloy Composition Semi-product Rm, MPa Rp0.2, MPa Ductility,%
AZ31B-F 3.0Al-1.0Zn bars, shapes 260 200 15
AZ61A-F 6.5Al-1.0Zn bars, shapes 310 230 16
AZ80A-T5 8.5Al-0.5Zn bars, shapes 380 240 7
AZ82A-T5 8.5Al-0.5Zn bars, shapes 380 275 7
AZ31B-H24 3.0Al-1.0Zn sheet, plates 290 220 15

38. • Mg-Zn-Zr alloys (ZK)
– Zn → strength improvement
– Zr → fine grain → improvement of strength, formability and corrosion resistance
– Better plasticity after heat treatment
– Alloying with RE a Cd → tensile strength up to 390 MPa
– Application up to 150 °C
• Mg-Mn alloys (M)
– Good corrosion resistance, hot formability, weldability
– Not hardenable → lower strength
Alloy Composition Semi-product Rm, MPa Rp0.2, MPa Ductility, %
ZK60A-T5 5.5Zn-0.45Zr bars, shapes 365 305 11
M1A-F 1.2Mn bars, shapes 255 180 12

39. • Mg-Th-Zr (HK)
– High temperature alloys
– Example: alloy HK31A - service temperature 315 to 345 °C
• Mg-Th-Mn (HM)
– Medium strength
– Creep resistance → service temperature up to 400 °C
• Mg-Y-RE (WE)
– Hardenability, formability, good weldability
– Y → strength after hardening, Nd → heat resistance, Zr → grain refinement
– Application to 250 °C
alloy composition semi-product Rm, MPa Rp0.2, MPa ductility, %
HM21A-T8 2.0Th-0.6Mn sheet, plates 235 130 11
HK31A-H24 3.0Th-0.6Zr sheet, plates 255 160 9
Mg-RE (WE) 8.4Y-0.5Mn-
0.1Ce-0.35Cd
bars, shapes 410 360 4

40. Cast magnesium alloys
• Basic systems
– Mg-Al-Mn with or without Zn (AM, AZ)
– Mg-Ag-RE (QE)
– Mg-Y-RE (WE)
– Mg-Zn-Zr with or without rare earth (ZK, ZE, EZ)
• Pressure die castings
- alloys AZ → excellent castability, good corrosion resistance in sea water
- aloys AM → good castability, corrosion resistance, better ductility and lower
strength
- castings are not heat treated
• Sand and permanent mold castings
- used mostly in heat treated state

41. • Typical properties of several cast magnesium alloys
alloy composition product Rm
MPa
Rp0.2
MPa
ductility
%
AM60A-F 6.0Al-0.13Mn pressure die
casting
205 115 6
AZ91A-F 9.0Al-0.13Mn-
0.7Zn
pressure die
casting
230 150 3
AZ63A-T6 6.0Al-3.0Zn-
0.15Mn
sand casting 275 130 5
AZ91C-T6 8.7Al-0.13Mn-
07Zn
sand casting 275 145 6
AZ92A-T6 9Al-2Zn-0.1Mn sand casting 275 150 3
AM100A-
T61
10.0Al-0.1Mn sand casting 275 150 1
QE22A-T6 2.5Ag-2.1RE-0.7Zr sand casting 260 195 3
WE43A-T6 4.0Y-3.4RE-0.7Zr sand casting 250 165 2
ZK61A-T6 6.0Zn-0.7Zr sand casting 310 195 10
EZ33A-T5 3.3RE-2.7Zn-0.6Zr sand casting 160 110 2

42. Titanium Alloys

43. Characteristics of titanium and titanium alloys
• Pure titanium - 2 modifications
– αTi – to 882 °C, hexagonal lattice
– βTi – 882 to 1668°C, cubic body centered lattice
– With alloying elements, titanium forms substitution solid solutions α and β
• Commercially pure titanium can be used as structural material in many applications,
but Ti alloys have better performance.
• Basic advantages of Ti
– Lower density comparing steel ( ρ = 4.55 g/cm³)
– High specific strength at temperatures 250 – 500 °C, when alloys Al, Mg already cannot
be used
– High strength also at temperatures deep below freezing point
– Good fatigue resistance (if the surface is smooth, without grooves or notches)
– Excellent corrosion resistance due to stabile layer of Ti oxide
– Good cold formability, some alloys show superplasticity
– Low thermal expansion => low thermal stresses

44. • Shortages of titanium
– High manufacturing costs => high prices (~8x higher comparing Al)
– Chemical reactivity above 500 °C – intensive reactions with O2, H2, N2, with refractory
materials of furnaces and foundry molds => brittle layers, which are removed with
difficulties
– Lower modulus of elasticity comparing steel ( E = 115 GPa against 210 GPa)
– Poor friction properties, tendency for seizing
– Poor machinability (low thermal conductivity → local overheating, adhering on tool,
above 1200 °C danger of chips and powder ignition.
– Welding problems (reactivity with atmospheric gases => welding in inert gas, diffusion
welding, laser beam welding, electron beam welding)
– Special manufacturing methods (vacuum melting and heat treating, manufacture of
castings in special molds – graphite molds and/or ceramic molds with a layer of carbon,
hot isostatic pressing - HIP)
• Preferred use of titanium alloys
– If strength and temperature requirements are too high for Al or Mg alloys
– At conditions, when high corrosion resistance is required
– At conditions, when high yield strength and lower density comparing steel are required
– Compressor discs, vanes and blades, beams, flanges, webs, landing gears, pressure
vessels, skin up to 3M, tubing…
– Increasing usage (Boeing 727 – 295 kg, Boeing 747 – 3400 kg)

45. Classification of titanium alloys
• Alloying elements
– α – stabilizers (Al, O, N, C) – stabilize solid solution α and enlarge zone of its existence
– β – stabilizers – stabilize solid solution β, decrease temperature α-β transformation
• β stabilizers forming eutectoid phase (Si, Cr, Mn, Fe, Co, Ni, Cu)
• β stabilizers isomorphic (V, Mo, Nb, Ta)
– Neutral elements (Sn, Zr) – only small influence on the α-β transformation
Phase diagrams of Ti with different stabilizers (solid
state)

46. • Classification of alloys according to microstructure after annealing
– α alloys – microstructure consists of homogeneous solid solution α
– pseudo α alloys (solid solution α + 5% solid solution β at most)
– α+β alloys – microstructure consists of mixture solid solutions α and β
– β alloys – microstructure consists of homogeneous solid solution β
– pseudo β alloys (solid solution β + small amount solid solution α)
– Alloys consisting of intermetallic compouds
• Classification according to usage
– Wrought alloys
– Cast alloys
• Designation of titanium alloys according to EN 2032-1
• Wrought material TI-PXXXXX
• Cast material TI-CXXXXX
• Product of powder metallurgy TI-RXXXXX
• First two digits represent main alloying elements (1-Cu, 2-Sn, 3-Mo, 4-V, 5-Zr, 6-Al,
7-Ni, 8-Cr, 9-others), TI-P64005 (Ti-6Al-4V), TI-P99XXX (pure titanium)
• Designation according to basic chemical composition (e.g. Ti-6Al-4V)

47. Properties of important wrought titanium alloys
Alloy Temper Rm, MPa Rp0.2, MPa Elongation,
%
E, GPa
α and pseudo α
Ti-5Al-2,5Sn annealed 790 - 860 760 - 807 16 110
Ti-5,6Al annealed 875 750 8 -
Ti-11Sn-1Mo-2,2Al-
5Zr-0,2Si
annealed 1000 - 1100 900 - 990 15 114
α + β
Ti-3Al-2,5V annealed 620 - 690 520 - 585 20 107
Ti-6Al-4V hardened
annealed
1170
900 - 990
1100
830 - 920
10
14
114
Ti-6Al-2Sn-2Zr-2Cr-
2Mo-0,25Si
hardened 1275 1140 11 122
pseudo β and β
Ti-10V-2Fe-3Al hardened 1170 - 1275 1100 - 1200 10 112
Ti-15V-3Cr-3Al-3Sn hardened 1095 - 1335 985 - 1245 6 - 12 -

48. Cast titanium alloys
• Comparison with wrought alloys
– Similar chemical composition
– Higher content of impurities, specific casting structure and defects (e.g. porosity)
– Lower ductility and fatigue life
– Often better fracture toughness
• Manufacture of shape castings
– Good casting properties (fluidity, mold filling)
– Hydrogen absorption, porosity
– Vacuum melting, special molds, hot izostatic pressing of castings (HIP)
• HIP – heating close to solidus + pressure of inert gas (elimination and welding of voids due to
plastic deformation) – conditions 910 to 965 °C/100 MPa/2 h.
Alloy Heat Treatment Rm, MPa Rp0.2, MPa A5 , %
Ti-6Al-4V stress relief annealing 880 815 5
Ti-6Al-2Sn-4Zr-2Mo 970°C/2h + 590°C/8h 860 760 4
Ti-15V-3Cr-3Al-Sn 955°C/1h + 525°C/12h 1120 1050 6
Examples of cast alloys

49. Composite Materials

50. Most composites consist of a bulk material (the ‘matrix’), and a
reinforcement, added primarily to increase the strength and stiffness of the
matrix. This reinforcement is usually in fibre form.
Today, the most common man-made composites can be divided into three main
groups:
Polymer Matrix Composites (PMC’s) – These are the most common and will
be discussed here. Also known as FRP - Fibre Reinforced Polymers (or Plastics)
– these materials use a polymer-based resin as the matrix, and a variety of fibres
such as glass, carbon and aramid as the reinforcement.
Metal Matrix Composites (MMC’s) - Increasingly found in the automotive industry,
these materials use a metal such as aluminium as the matrix, and reinforce it with fibres
such as silicon carbide (SiC).
Ceramic Matrix Composites (CMC’s) - Used in very high temperature
environments, these materials use a ceramic as the matrix and reinforce it with short fibres,
or whiskers such as those made from silicon carbide and boron nitride (BN).

51. Polymer fibre reinforced composites
Common fiber reinforced composites are composed of
fibers and a matrix.
Fibers are the reinforcement and the main source of strength
while the matrix 'glues' all the fibres together in shape
and transfers stresses between the reinforcing fibres.
Sometimes, fillers or modifiers might be added
to smooth manufacturing process, impart special properties,
and/or reduce product cost.

52. Polymer matrix composites
• The properties of the composite are determined by:
- The properties of the fibre
- The properties of the resin
- The ratio of fibre to resin in the composite (Fibre Volume Fraction)
- The geometry and orientation of the fibres in the composite
Properties of unidirectional
composite material

53. Main resin systems
• Epoxy Resins
The large family of epoxy resins represent some of the highest performance resins of those
available at this time. Epoxies generally out-perform most other resin types in terms of
mechanical properties and resistance to environmental degradation, which leads to their
almost exclusive use in aircraft components
• Phenolics
Primarily used where high fire-resistance is required, phenolics also retain their properties
well at elevated temperatures.
• Bismaleimides (BMI)
Primarily used in aircraft composites where operation at higher temperatures (230 °C
wet/250 °C dry) is required. e.g. engine inlets, high speed aircraft flight surfaces.
• Polyimides
Used where operation at higher temperatures than bismaleimides can stand is required (use
up to 250 °C wet/300 °C dry). Typical applications include missile and aero-engine
components. Extremely expensive resin.

55. Fabric types and constructions
• Unidirectional fabrics
– The majority of fibres run in one direction only, a small amount of fibre may run in
other directions to hold the primary fibres in position
– Prepreg unidirectional tape- only the resin system holds the fibres in place
– The best mechanical properties in the direction of fibres
• Basic woven fabrics
– Plain -Each warp fibre passes alternately under
and over each weft fibre. The fabric is
symmetrical, with good stability. However,
it is the most difficult of the weaves to drape.
– Twill - One or more warp fibres alternately weave
over and under two or more weft fibres in a regular
repeated manner. Superior wet out and drape,
smoother surface and slightly higher mechanical
properties

56. Fabric types and constructions – cont.
– Basket -Basket weave is fundamentally the same
as plain weave except that two or more warp fibres
alternately interlace with two or more weft fibres.
An arrangement of two warps crossing two wefts
is designated 2x2 basket.It is possible to have 8x2,
5x4, etc. Basket weave is flatter, and, through
less crimp, stronger than a plain weave, but less stable.
• Hybrid fabric
– A hybrid fabric will allow the two fibres to be presented in just one layer of fabric.
– Carbon / Aramid - The high impact resistance and tensile strength of the aramid
fibre combines with high the compressive and tensile strength of carbon.
– Aramid / Glass - The low density, high impact resistance and tensile strength of
aramid fibre combines with the good compressive and tensile strength of glass,
coupled with its lower cost.
– Carbon / Glass - Carbon fibre contributes high tensile compressive strength and
stiffness and reduces the density, while glass reduces the cost.

58. Properties of composites
• UD laminate
Properties directionally
dependent
• Quasi-isotropic laminate
Properties nearly equal in all
directions
Tensile
strength,
MPa
Angle between fibers and stress, °

59. Properties of epoxy UD prepreg laminates
Fibre fracture volume typical for aircraft structures
Prepreg
Fabrics and fibres are pre-impregnated by the materials manufacturer with a pre-catalysed
resin. The catalyst is largely latent at ambient temperatures giving the materials several
weeks, or sometimes months, of useful life. To prolong storage life the materials are stored
frozen (e.g. -20°C). High fibre contents can be achieved, resulting in high mechanical
properties.

61. Fiber metal laminates
• Consist of
alternating thin
metal layers and
uniaxial or biaxial
glass, aramid or
carbon fiber
prepregs

62. Fibre metal laminates
• Developed types
- ARALL - Aramid Reinforced ALuminium Laminates (TU-DELFT)
- GLARE - GLAss REinforced (TU-DELFT)
- CARE - CArbon REinforced (TU-DELFT)
- Titanium CARE (TU-DELFT)
- HTCL - Hybrid Titanium Composite Laminates (NASA)
- CAREST – CArbon REinforced Steel (BUT - IAE)
- - T iGr – Titanium Graphite Hybrid Laminate (The Boeing Company)
• Advantages
Fibre metal laminates produce remarkable improvements in fatigue
resistance and damage tolerance characteristics due to bridging
influence of fibres. They also offer weight and cost reduction and
improved safety, e.g. flame resistance. They can be formed to limited
grade.

63. Standard FML configurations
Type Configuration Metal alloy Prepreg
constituents
Prepreg
orientation
ARALL 2 2/1 – 6/5 2024-T3 Aramid-epoxy unidirectional
ARALL 3 2/1 – 6/5 7475-T76 Aramid-epoxy unidirectional
GLARE 1 2/1 – 6/5 7475-T76 Glass-epoxy unidirectional
GLARE 2 2/1 – 6/5 2024-T3 Glass-epoxy unidirectional
GLARE 3 2/1 – 6/5 2024-T3 Glass-epoxy Cross-ply
GLARE 4 2/1 – 6/5 2024-T3 Glass-epoxy Cross-ply
/unidirectional

64. Mechanical properties of FML
Laminate Metal
thickness
mm
Prepreg
thickness
mm
Tensile
strength
MPa
Yield
strength
MPa
E
GPa
Density
g/ccm
ARALL 1 0.3 0.22 897 535 67.5 2.16
ARALL 2 0.3 0.22 849 411 68.3 2.16
GLARE 1 0.3 0.25 1494 530 62.2 2.42
GLARE 2 0.2 0.25 1670 416 60.9 2.34
0.3 0.25 1449 406 63.0 2.42
0.4 0.25 1295 399 64.5 2.47
GLARE 3 0.3 0.25 849 382 51.3 2.42

65. Fatigue resistance of FML comparing to 2024 alloy

66. GLARE fire resistance comparing to 2024 alloy

67. Fiber metal laminates - application
AIRBUS A 380
Panels of fuselage upper part – 470 m² , GLARE 4
Maximum panel dimensions 10.5 x 3.5 m
Weight saving - 620 kg
Adhesive bonded stringers from 7349 alloy

68. Sandwich materials
• Structure – consists of a lightweight core
material covered by face sheets on both
sides. Although these structures have a
low weight, they have high flexural
stiffness and high strength.
• Skin (face sheet)
– Metal (aluminium alloy)
– Composite material
• Core
– Honeycomb – metal or composite
(Nomex)
– Foam – polyurethan, phenolic,
cyanate resins, PVC
• Applications – aircraft flooring,
interiors, naccelles, winglets etc.
Sidewall panel for Airbus A320

69. Effectivness of sandwich materials

70. List of problems (light alloys)
What are the main advantages of aluminium alloys for applications in aircraft structures?
What numerical designation system is used for identification of wrought aluminium alloy?
What is meaning of the first digit?
What groups of wrought aluminium alloys are usually used in aircraft structures?
Explain the designation of the following alloys:
- 2024 T4
- 7075 T6
- Alclad 2219
Why is sheet from 2xxx alloys often clad with pure aluminium?
What group of wrought aluminium alloys exhibits the best mechanical properties?
Compare alloys 6056 and 7050!
What are the main advantages and limitations of Al-Li alloys comparing to other Al alloys?
What is a common value of aluminium alloys elastic modulus in tension?
Recommend the alloys for aircraft skin!
Why are Mg alloys valuable for aerospace application?
What is damping capacity of magnesium alloys?
What are the main reasons for using of titanium alloys in airframe and engine structures?
What titanium alloy is the most widely used?
Compare the specific tensile strength and specific tensile modulus of 2090 and Ti-6Al-4V
alloys!
- (Specific value = value/density)

71. List of problems (composite and sandwich materials)
What is composite material?
What are advantages of composites comparing to metals?
What is prepreg?
What are common types of fibres?
What fibres have the highest specific tensile strength and specific tensile modulus?
( the specific property is the ratio value/density )
What is main role of matrix?
What are main advantages of epoxy, phenolic and bismaleimide (polyimide) matrices?
What are main advantages of using prepregs?
How the fibre orientation influences resulting mechanical properties of a composite?
What are typical tensile properties of epoxy prepregs UD laminates along and across fibres?
What is structure of sandwich material?
What are main advantages of sandwich panels compared to solid panels?
What materials are usually used for sandwich skins and core?