Composite Materials Dr. Jing LI 13661954020 55271689 lijing6080@usst.edu.cn 2014-2015 Fall Semester

Composite Materials

Dr. Jing LI13661954020

55271689lijing6080@usst.edu.cn

2014-2015 Fall Semester

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