1. Composite Materials Dr. Jing LI 13661954020 55271689
Fall Semester

2. Definition of Composite Materials
A multi-phase material, consisting of two or more physically distinct and mechanically separable constituents.
One phase is usually continuous and is designated the “matrix”
The other phase(s) are reinforcements distributed within the matrix and may be fibrous or particulate
In some composites there may be two interpenetrating continuous phases.

5. Composites offer High Strength Light Weight Design Flexibility
Consolidation of Parts
Net Shape Manufacturing
Functional Properties
Electrical conductivity
Thermal management
Physical barriers

6. Classification of Composites (I)
1) Natural Composite Materials:
Wood; bamboo; bones; muscles and other tissues
2) Microcomposites
Metallic alloys, Polymer blends, Fibre reinforced composites (PMCs, MMCs, CMCs); Particulate reinforced composites
3) Macrocomposites
Coated sheets-galvanized steel
Laminate composites
Sandwiches-honeycomb and foam structure
4) Nanocomposites
Polymer composites reinforced with clay minerals, BN, fullerence, Carbon nanotubes, Graphene.

7. Classification of Composites (II)
Particulate
Fiber
Structural
Large
Dispersion
Laminates
Sandwich
Particle
Strengthened
Panels
Continuous
Discontinuous
Aligned
Random
Particle size< 10-8m

8. Classification of Composites (III)
Metal matrix composites
Ceramic matrix composites
Polymer matrix composites

9. Design Project
Propose a project which designs one composite materials.
The project must have a real application
Send me the project title by the end of week 7 (October 11th).
The title must clearly indicate what product will be designed.

10. Design Project Present the project on December 16th
Including the survey of the materials in the commercial products. (the fulfilled properties, the critical properties, the desired properties)
The composite materials design. (matrix, reinforcement, the geometry, advantage)
Calculate the filler content according to the required material properties.
Proposed fabrication method.
Discussion and Conclusion：Is your design better than the commercial available products.

11. Properties of Composites
Dependent on:
Constituent phases
relative amounts
geometry of dispersed phase
shape of particles
particle size
particle distribution
particle orientation
Interface properties
Processing Methods

13. Functions of Matrix (Primary phase)
Continuous phase
Provides the bulk form of the part or product.
Supporting the fibre
Holds the imbedded phase in place, usually enclosing and often concealing it .
Providing adequate environmental protection
Transfer of load through the fibre-matrix interface (mainly by shear)

14. Matrix Considerations
End Use Temperature
Toughness
Cosmetic Issues
Flame Retardant
Processing Method
Adhesion Requirements

15. The Reinforcing Phase (Secondary Phase)
A reinforcement is the strong, stiff integral component of a composite which is incorporated into the matrix to achieve desired properties
Imbedded phase is the most common one
The secondary phase can take the form of an infiltrated phase in a skeletal or porous matrix
Example: a powder metallurgy part infiltrated with polymer

16. Functions of reinforcements
Function is to reinforce the primary phase
The term ‘reinforcement’ implies some property enhancement
Fibres or Filaments: continuous fibres, discontinuous fibres, whiskers
Particulates reinforcements may be of any shape, ranging from irregular to spherical, plate-like or needle-like, nanoparticles (clay, carbon black)

17. Textile Structure Unidirectional Woven Braid

19. The Interface
There is always an interface between constituent phases in a composite material
For the composite to operate effectively, the phases must bond where they join at the interface
Figure ‑ Interfaces between phases in a composite material: (a) direct bonding between primary and secondary phases

20. Interphase
In some cases, a third ingredient must be added to achieve bonding of primary and secondary phases
Called an interphase, this third ingredient can be thought of as an adhesive
Figure ‑ Interfaces between phases: (b) addition of a third ingredient to bond the primary phases and form an interphase

21. Characteristics of Composites
Heterogeneity
Composites are always heterogeneous, often at several different level of structure. They cannot be treated as “continuous solids”.
Fibre: 1.0 –20 mm
Lamina: 0.1 –1.0 mm
Laminate: 1.0 –100 mm
Component: 0.1 – 10m
Property Relationships
Their properties are determined by those of constituents, their relative concentrations, their geometric arrangement, manufacturing processes and the nature of the interface between them.
Anisotropy
Composites are sometimes strongly anisotropic: properties are different in one direction than in another. This requires a fundamentally different approach to both design and manufacture.
Fibre/Laminate: axial/transverse

22. Advantages of Composites
Mechanical
High specific stiffness and strength
Enhanced Toughness
Enhanced fatigue properties
Better damage tolerance
Physical
Controlled thermal expansion and conductivity
Directional electrical and magnetic properties
Better elevated temperature behaviour
Better barrier properties
Chemical
Enhanced corrosion and degradation resistance

23. Advantages of Composites in Service
Structural efficiency
Lower mass
Longer (flight) range
Lower fuel consumption
Higher performance
Enhanced Durability
Longer life
Extension of operating envelope (e.g. higher temp)
Less maintenance
Greater reliability
Lower operating cost

24. Summary Definition of composite materials
Classification of composite materials
Functions of matrix and reinforcements
Applications of composite materials
Advantages of composite materials
Factors determine the performace of composite materials