This document contains slides from a lecture on composites and particle-reinforced composites. It defines composites as materials composed of two or more constituent materials or phases, and discusses their classification. In particular, it examines particle composites, including large-particle composites and dispersion-strengthened composites. It explores how particle size and distribution affect properties like elastic modulus, and gives examples of particle composites like cemented carbides and automobile tires.

1. ENR116 – Mod. 4- Slide No. 1
ENR116 Engineering Materials
Module 4 Non-metals and Corrosion
Dr David Steele
Unit Coordinator
School of Advanced Manufacturing and Mechanical Engineering

2. ENR116 – Mod. 4- Slide No. 2
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3. ENR116 – Mod. 4- Slide No. 3
Particle-reinforced
composites

4. ENR116 – Mod. 4- Slide No. 4
Intended Learning Outcomes
At the end of this section, students will be able
to:-
• Understand what composites are and how they
are classified.
• Reason why composites are used in place of
other material types.

5. ENR116 – Mod. 4- Slide No. 5
fibreglass
Carbon fibres
concrete
Composites
By cobalt123,
released under CC
BY-NC 2.0 license
By Red~Cyan,
released under CC
BY-NC 2.0 license

6. ENR116 – Mod. 4- Slide No. 6
Mat. Res. vol.9 no.3 2006
Airbus A380
Composites make up more than
20% of the A380's airframe.
GLARE (GLAss-REinforced
fibre metal laminate).
By Jun Acullador, released under
CC BY-NC 2.0 license

7. ENR116 – Mod. 4- Slide No. 7
Composites: Composed of two (or more) individual materials
from the categories of metals, ceramics and polymers.
Composites
A composite is considered to be any multiphase material that
exhibits a significant proportion of the properties of both
constituent phases such that a better combination of
properties is realized.
Material
class
Tensile
Strength
Elastic
Modulus
Ductility Toughness Density
Metals Good Good OK Good Poor
Polymers Poor Poor Good Poor Good
Ceramics Good Good Poor Poor OK
COMPOSITES

8. ENR116 – Mod. 4- Slide No. 8
Wood: A natural composite of
cellulose fibres (which are
strong in tension) embedded in
a matrix of lignin which resists
compression.
Natural composites

9. ENR116 – Mod. 4- Slide No. 9
The simplest composite materials are composed of just two
phases; the matrix, which is continuous and surrounds the
other phase, often called the dispersed phase.
Composites
Adapted from Fig. 16.1(a), Callister & Rethwisch 8e.

10. ENR116 – Mod. 4- Slide No. 10
Composites: Multiphase material with significant presence of
each phase.
Matrix: The continuous phase. Fills volume, provides shape.
Transfers stress to other phase(s) and protect phases from the
environment.
Terminology and classification
Dispersed Phase: Enhances matrix properties. May increase
E, y, TS or creep resistance.
metal ceramic polymer
Classification:
MMC, CMC, PMC

11. ENR116 – Mod. 4- Slide No. 11
Composite classification
Large-
particle
Dispersion-
strengthened
Particle-reinforced
Continuous
(aligned)
Aligned Randomly
oriented
Discontinuous
(short)
Fiber-reinforced
Laminates Sandwich
panels
Structural
Composites
Adapted from Fig. 16.2,
Callister & Rethwisch 8e.

12. ENR116 – Mod. 4- Slide No. 12
Particle composites
Particle-reinforced Fiber-reinforced Structural
Large-particle composites: particle-matrix interactions cannot
be treated on the atomic or molecular level.
The particulate phase is harder and stiffer than the matrix.
Cheap fillers: reduces cost (as the particles are much less
expensive than the matrix).
Resist localised deformations: Particles tend to restrain
movement of the matrix phase in the vicinity of each particle.

13. ENR116 – Mod. 4- Slide No. 13
Dispersion-strengthened composites:
Particles smaller: diameters between 10 and 100 nm.
Particle composites
Particle-reinforced Fiber-reinforced Structural
The small dispersed particles hinder or impede the motion of
dislocations (plastic deformation).
Yield and tensile strengths, hardness are improved.

14. ENR116 – Mod. 4- Slide No. 14
1. Large-particle:
Particles should be evenly distributed throughout the matrix.
Particle composites
Particle-reinforced Fiber-reinforced Structural
Mechanical properties are enhanced with increasing
particulate content.
2. Dispersion strengthened:
Matrix supports load, small
particles stop crack propagation

15. ENR116 – Mod. 4- Slide No. 15
Particle composites
Elastic modulus, Ec:
Application to other properties:
Electrical conductivity, e: Replace E’s in equations with e’s.
Thermal conductivity, k: Replace E’s in equations with k’s.
Adapted from Fig. 16.3,
Callister & Rethwisch 8e.
(Fig. 16.3 is from R.H.
Krock, ASTM Proc, Vol.
63, 1963.)
lower limit:
1
Ec
=
Vm
Em
+
Vp
Ep
upper limit: c m m
E = V E + VpEp
Data:
Cu matrix
w/tungsten
particles
0 20 40 60 80 100
150
200
250
300
350
vol% tungsten
E(GPa)
(Cu) (W)
Two ‘rule of mixture’ extremes:

16. ENR116 – Mod. 4- Slide No. 16
Particle composites
Particle-reinforced Fiber-reinforced Structural
Adapted from Fig.
16.4, Callister &
Rethwisch 8e. (Fig.
16.4 is courtesy
Carboloy Systems,
Department, General
Electric Company.)
- WC/Co
cemented
carbide
matrix:
cobalt
(ductile,
tough)
particles:
WC
(brittle,
hard)
:
600mm
Adapted from Fig.
16.5, Callister &
Rethwisch 8e. (Fig.
16.5 is courtesy
Goodyear Tire and
Rubber Company.)
- Automobile
tire rubber
matrix:
rubber
(compliant)
particles:
carbon
black
(stiff)
0.75mm

17. ENR116 – Mod. 4- Slide No. 17
From ciks.cbt.nist.gov
Particle composites
Concrete - gravel + sand + cement + water
Reinforced concrete - Reinforce with steel rebar or
remesh - increases strength - even if cement matrix is
cracked.
Pre-stressed concrete - Rebar/remesh placed under
tension during setting of concrete. Release of tension after setting places
concrete in a state of compression. To fracture concrete, applied tensile stress
must exceed this compressive stress.
threaded
rod
nut
Post-tensioning – tighten nuts to place concrete under compression
Sand fills voids between gravel particles.

18. ENR116 – Mod. 4- Slide No. 18
Summary
• Composites are classified according to both
the matrix material and reinforcement
structure.
• Composites enhance mechanical properties
such as Young’s modulus and stress.

19. ENR116 – Mod. 4- Slide No. 19
Thank you