4. Page 4
Background
Metal Matrices Composites (MMCs) have a series advantages:
High Specific Strength High Modulus Ratio
High Thermal Conductivity High Electrical Conductivity
Low Thermal Expansion Coefficient
Excellent Irradiation Resistance
Good Thermal Endurance Anti-flammability
Non-hygroscopic Non Gas Effusion
MMCs have Broad Applications in High-Tech Fields:
Aerospace Aviation
Electronics Automobiles
Advanced Weapon Systems
5. Page 5
Background
Aircraft structure can reach 300 ℃ @ 3 times
sound speed flight
High-speed flight → Aerodynamic heating &
surface friction → High temperature
Temperature influence to Cf/Al composites
mechanical properties
Theoretical basis for Cf/Al composites
application in Aerospace Field
24. Page 24
Analysis
Interfaces decide composite strength
Reinforcement -- Main force carrier
Matrix -- Distribute strength in composite
Interfaces -- Transfer loads to reinforcement
25. Page 25
Analysis
Weak interface
Failure under lower stress
Difficult to transfer load to reinforcement
Poor Mechanical properties
26. Page 26
Analysis
Strong interface
Cracks at interface extend easily
Interface adjust stress distribution poorly
Local stress concentration → low stress failure
Brittle Fracture no fibers extracted
27. Page 27
Analysis
Moderate Interface
Cracks at interface extend gentlely
Certain amount fibers extracted
Energy depleted in discombination of fibers and matrix
Best Mechanical Properties
37. Page 37
Element Wt% At%
C K 31.21 50.21
O K 00.59 00.71
MgK 03.05 02.42
AlK 65.15 46.66
SiK 00.00 00.00
Fracture Morphology Observation
Filamentous Al appear on surface of Carbon
Fibers in Cf/5A06Al Under 400℃ Condition
38. Page 38
Element Wt% At%
C K 62.09 78.04
O K 01.89 01.78
MgK 00.45 00.28
AlK 35.57 19.90
SiK 00.00 00.00
500℃
Fracture Morphology Observation
Filamentous Al appear on surface of Carbon
Fibers in Cf/6061Al Under 500℃ Condition
No Filamentous Al appear on Cf surface in
Cf/6061Al Under 400℃ Condition
39. Page 39
TEM Microstructure Observation
TEM Microstructure of Cf/6061Al Composite Three-Point Bending Test
Specimen Under 300℃ Condition
a) Dislocations in Matrix
b) Interphase Precipitate Phase
c) Precipitate Phase Diffraction Spots
40. Page 40
TEM Microstructure Observation
TEM Microstructure of Cf/6061Al Composite Three-Point Bending Test
Specimen Under 500℃ Condition
a) Acicular Precipitate Phase
b) Matrix Diffraction Spots
c) Precipitate Phase Diffraction Spots
41. Page 41
TEM Microstructure Observation
TEM Microstructure of Cf/5A06Al Composite Three-Point Bending Test
Specimen Under 300℃ Condition
a) Dislocations in Matrix
b) c) Interphase Precipitate Phase
43. Page 43
Conclusions
Bending Strength Elastic Modulus Bending Deflection Interface
Cf/6061 771MPa
300℃
178GPa
300℃
20×Room T Deflect
500℃
Strong
Interface
Cf/5A06 1207MPa
100/200℃
240GPa
350℃
6×Room T Deflect
500℃
Moderate
Interface
25℃ 300℃ 500℃
Cf/6061 Much Brittle Phase Al4C3 Less Brittle Phase Al4C3 Al Matrix soften Al2O3
Cf/5A06 No Brittle Phase Al4C3 Brittle Phase Al58Mg42 Al Matrix soften Al2O3
Critical Values
Phase @ Interface
44. Page 44
Conclusions
Temperature Variations of Mechanical Properties are the
same -- increase first and then decrease
Cf/6061Al Temperature Variation lags behind Cf/5A06Al
Cf/5A06Al has better Mechanical properties in general &
fits high temperature condition better
Recommend Cf/5A06Al to applications in Aerospace
Engineering & Advanced Weapon Systems
