composite materials dr. jing li 13661954020 55271689 [email protected] 2014-2015 fall semester
TRANSCRIPT
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.
Composites offer High StrengthLight WeightDesign FlexibilityConsolidation of PartsNet Shape ManufacturingFunctional Properties
Electrical conductivity Thermal management Physical barriers
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.
Classification of Composites (II)Composites
Particulate Fiber Structural
Continuous Discontinuous
Laminates SandwichPanels
LargeParticle
DispersionStrengthened
Aligned Random
Particle size< 10-8m
Classification of Composites (III)
Metal matrix composites Ceramic matrix composites Polymer matrix composites
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.
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.
Design Project
Properties of CompositesDependent on: Constituent phases
relative amounts geometry of dispersed phase
shape of particles particle size particle distribution particle orientation
Interface properties Processing Methods
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)
Matrix Considerations
End Use TemperatureToughnessCosmetic IssuesFlame RetardantProcessing MethodAdhesion Requirements
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
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)
Textile StructureUnidirectionalWovenBraid
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
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
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 m 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
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
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
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