CHEM-E2200: Polymer blends and

composites

Introduction
Mark Hughes & Jon Trifol Guzman
7th September 2020
Today

• Course outline
• Passing the course!
• Composites: examples, manufacture, applications
• Fundamental concepts: reinforcement, matrix and
interface; volume fraction
Why this course?
• To underpin the development of new fibre (reinforced)
materials an excellent understanding of composite materials is
essential
• The science and technology of these synthetic materials is well
understood and continues to develop. Notable developments in
transportation and aerospace
• Much can be learnt from these sectors and applied to
composite reinforced with other fibre types, such as natural
bio-based fibres and their derivatives
• This course provides a grounding for further study and
developments
 Learning outcomes
• Is familiar with the potential of synthetic polymers in composite
technology
• Knows the role of reinforcement, matrix and interface in a composite
system
• Knows the principles of load sharing and reinforcement processes in
short and long fibre reinforced composites and the influence of fibre
architecture on composite properties
• Can use simple micromechanical models to predict selected
composite properties
• Can evaluate the compatibility between polymer and
reinforcement/filler systems and is familiar with the main methods of
controlling compatibility
• Knows the methods to process thermosetting and thermoplastic
polymer composites into various products
• Can make a literature study and present his/her study orally
Perspective
• Principally we will consider micro-scale reinforcement,
though we will discuss the utilisation of nanoscale
reinforcement and fillers
• We will generally consider composites as engineering
materials and so the main emphasis will be on
mechanical properties and the factors that govern
these. In particular strategies that might enable us to
improve the performance of low environmental
impact composites
Content
• Composites theory
– Reinforcement, matrix and interface
– Load sharing and stress-transfer
– Fibre architecture
– Elastic deformation in long and short fibre composites
– Deformation and fracture behaviour
• Raw materials (fibres and matrices)
– Types, sources and properties
– Polymers, virgin, recycled, fossil-based, biopolymers
• Processes
– Composites processing for thermoplastics and thermosetting resins
– Fibre processing, including modification
• Applications
Passing the course!

• 6 weeks in period I of the Autumn term 2020

• 5 credit course
• 1 x 2 hour session per week (+ additional lecture on Tuesday
22nd September)
• Assessment:
– Project: 60% (45% report; 15% presentation)
– Examination*: 40%

*This will be in the form of a “home” exam. Please see following slide for details
Special arrangements for 2020
• This year all classes and sessions will be online! We will use Zoom for the “live”
lecture sessions that will be given at the specified time. As in previous years, the
slides will be put in MyCourses beforehand.
• Please try to attend the lectures as we use these to convey ideas and concepts,
rather the regurgitate facts that you can easily find online! We plan to make
them as interactive as possible, given the limitations of the online environment.
• For privacy reasons, we cannot share recordings of the interactive parts of the
lecture, so will not record the “live” lectures. If you have questions just ask!!
• This will be a relatively new experience for all of us, so let’s keep an open mind
to ways of improving things!
• You will be assessed by a “home” exam to replace the usual formal written
exam. In this, the format will differ in that you will be able to use materials (your
notes, books, scientific articles etc.) when completing your exam paper in your
home environment. More details will be given later….
Schedule
Date Topic Content Teacher(s)
7.9 Introduction Course intro and administrative matters. Mark Hughes
Composites; material property envelope; fibres; Jon Trifol Guzman
matrices; interface; manufacturing; applications;
basic concepts
14.9 Fibre Reinforcement geometry and scale; fibre volume Mark Hughes
‘architecture’ fraction and voids; packing arrangement; orientation
of reinforcement
21.9 Reinforcement Load sharing; elastic stress transfer (Cox shear-lag Mark Hughes
processes theory); stress transfer by slip; effect of aspect ratio;
deformation in long fibre composites (axial and
transverse)
22.9 Interfacial Enhancing the compatibility between fibre and Jon Trifol Guzman
effects matrix interface; measuring interfacial properties
28.9 Elastic Axial and transverse stiffness of unidirectional Mark Hughes
deformation of laminae; off-axis loading and interaction effects;
laminates multi-ply laminates
5.10 Manufacturing Manufacturing methods for thermoset and Jon Trifol Guzman
thermoplastic matrix composites
12.10 Strength and Inelastic processes; predicting the strength of Mark Hughes
failure composites; toughness
Project
• Completed in pairs
• Based on approximately 15-20 peer-review literature sources +
others as appropriate (will depend upon chosen topic)
• This is a ‘desk-based’ research project. The information that
you use will come form e.g.
– Scientific literature (principally)
– Internet (be critical about the information that you obtain)
– Direct contact with companies (if appropriate)
• Assessment:
– Report of around 15 pages of written text (please refer to guidelines)
– Presentation and discussion. Sessions will be arranged in week 42 (e.g.
13th, 14th or 15th October)
Project assessment
• Introduction (5 points)
– E.g. What is the rationale of the project. Provide the context (bigger picture). What are your hypotheses
and objectives?

• Scope and relevance (5 points)

– E.g. Is your project in the focus of the topic? Is it relevant to the topic?

• Content and depth (15 points)

– E.g. How deeply do you go in to the topic. Better to have a narrower focus and more depth than very
broad and superficial coverage.

• Use of literature (10 points)

– E.g. Not just the sources you use, but also how you discuss these in the context of your report.

• Conclusions (5 points)
– E.g. What can you conclude from your study. Concise and to the point.

• Presentation and style (5 points)

– E.g. Does your report follow normal scientific reporting style? Do you use references in the correct way
and are they listed correctly?
 Project
• Select a topic and confirm by e-mail to Mark and Jon
– Either Mark or Jon will mentor your project, depending upon the topic
• Send an outline of your first thoughts to Mark / Jon by 16.9
– This should be no more than a short document to outline your first thoughts
about the project (i.e. some background and rationale + objectives) and a
provisional list of contents. This need be no more than about 1 page, but
sufficient to convey your idea!
– We will give you written feedback on this and if you want to discuss with
either of us, please don’t hesitate to make contact!
• Submit a draft of your report (approx. 50% complete) by Monday 28th
September and arrange a Teams meeting with Mark / Jon to obtain
further feedback/comments about the project on one of the
following dates: 1st or 2nd October or 5th – 7th October
• Present your findings in one of two sessions organised at the end of
week 42 (13th, 14th or 15th October)
• Report deadline: Friday 30th October
Topics
You are free to propose your own topic so long as it is in line with the aims of the
course and supports the learning objectives! It is your chance to delve deeper into a
topic that is of interest to you! Here are some suggested topics, however:

• Measuring fibre-matrix bond strength in • Recycling of polymer composites

polymer matrix composites
• Textile reinforcement for composites
• A critical review of manufacturing
processes for thermosetting PMCs • Techniques in the micromechanical
• Processes for the manufacture of evaluation of composites
thermoplastic polymer matrix • Fracture and strength of composites
composites
• Additives used in biocomposites
• The potential of bio-based fibres as
reinforcement for composites • Biopolymer composites in medicine
• Carbon fibres from non-traditional • Self-healing polymer composites
precursors • Life Cycle Assessment (LCA) of
• Application of FRPs in ground biocomposites
transportation applications
• Damage analysis in polymer
• Polymer matrix composites in composites
construction
• Biomimetic polymer composites
Other matters

• Will keep MyCourses up to date with any new

information that becomes available
• Slides will be in MyCourses
Contact details:

• Mark Hughes (mark.hughes@aalto.fi; room 221,

Vuorimiehentie 1)
• Jon Trifol Guzman (jon.trifol@aalto.fi; Chemistry
building)
Reading material
• General introduction to materials:
– JE Gordon. “The New Science of Strong Materials or Why You Don't Fall
Through the Floor” (Princeton Science Library). BUY IT!
• Many books covering composite materials science:
– D. Hull, and T. W. Clyne. “An Introduction to Composite Materials”
(Cambridge Solid State Science Series) – available from Amazon and
copies are available in the library
– M.R. Piggott. “Load bearing fibre composites”
• Green composites:
– Caroline Baillie. “Green Composites” Woodhead Publishing Ltd
• Many others relating to composite materials
What is a composite?
“The whole is greater than the sum of its parts”
- Aristotle
• A composite is a material composed of two or more distinct
constituents (or phases) separated by an identifiable
interface
• Generally (but not always) the phases have different physical
and/or chemical properties
• The properties of the resulting composite can be entirely
different from those of the original components
• For example GRP (Glass-fibre Reinforced Plastic) is composed
of (brittle) glass and (also brittle) thermosetting polymer, but
the resulting composite is very ‘tough’ (the fracture energy is
about 103 to 104 times greater)
• Why is this? Structure (and particularly microstructure)
+

=
Toughening polymers with nanocellulose

PLA + 1% nanocellulose
x10 work of fracture
Mechanical properties

For many real-life engineering applications it is often

desirable to have a blend of properties:
• Good stiffness:
– resistance to deflection under short-term loading
• Adequate strength:
– how much force can be sustained before it breaks
• Toughness:
– the ability to resist the propagation of cracks (arguably
the most important property of an engineering material)
Stress, strain, stiffness, strength
• Stress: load/cross-sectional
area
• Strain: extension/original
length
• Poisson’s ratio: ratio of
transverse to axial strain
• Stiffness: Young’s modulus,
E, stress/strain (in linear
elastic region – Hooke’s law)
• Strength: stress at ultimate
load (tension or
(Source: Wikipedia) compression)
The range of properties that Nature can achieve

(Source: J.E. Gordon: “Structures”)

 1000

100
Composites

10

Plastics
Young's modulus (GPa)

0,1

0,01

0,001

Elastomers

1e-4
Foams

1e-5

10 100 1000
Density (kg/m^3)

Prepared using CES EduPack 2016

 (a) Young's modulus and (b) strength plotted against density for woods and their constituents.

Lorna J. Gibson J. R. Soc. Interface 2012;rsif.2012.0341

This journal is © 2012 The Royal Society

 (a) Young's modulus–density chart for engineering materials, including woods.

Lorna J. Gibson J. R. Soc. Interface 2012;rsif.2012.0341

This journal is © 2012 The Royal Society

Wood: the ultimate composite material?

Howard Hughes’
“Spruce Goose”

• Excellent specific mechanical properties

• Synthesized from CO2 and H2O (+sunlight)
• Completely biodegradable when required, but can last for millennia!
The hierarchical composite structure of
wood
Tree (100-102 m)

Structural timber
(100-101 m)

Anatomy (10-2 m)

Microstructure (10-3 m)

Cell wall (10-6 m)

Microfibrils (10-9 m)
Molecules (10-10 m)
Wood structure

(Source: Society of Wood Science and Technology)

Composite materials

• Composite materials are nowadays widely used by

humankind in many diverse applications
• Nature also uses composites extensively and many elegant
hierarchical composite structures have evolved that are far
more complex than any synthetic equivalents – we can learn
a lot from these natural materials!
• Natural composites have been, and are, used extensively by
humankind
• Many of the earliest forms of composite were based on
natural materials
Composites: natural, synthetic and natural-
synthetic hybrids…..
• FRPs - Fibre Reinforced Plastics: carbon, glass, aramid fibre:
epoxy, phenolic, unsaturated polyester resin
• Metal matrix composites - MMC
• Wood: cellulose embedded in hemicellulose and lignin
• Bone: hard crystalline mineral, hydroxyapatite, embedded in
a matrix of collagen
• Teeth, skin….. almost all biological materials are composites
of one sort or another….
• “Biocomposites” (the first manmade composites) combine at
least one “natural” component
Composites in Nature: their hierarchical structure

Cells Cell wall Microfibrils

Synthetic composites: simpler microstructures
Synthetic composites
Natural composites used by humans
Hybrids: wood plastic composites (WPC)
• Now in commercial
production in many
countries, especially in N.
America
• Europe slow to take-off, but
now strong interest. E.g.
UPM ProFi and UPM Formi
products
• Applications are mainly in
the construction sector,
where they can replace
materials such as treated
timber, but are extending
into other areas including
biomedical and other
consumer applications
Many manufacturing options depending on material,
application and production volume

Extrusion
Resin infusion

Dough
moulding
compound

Thermosetting and thermoplastic polymer matrices

Composites in history
• Hemp fibre found in ancient
pottery from China dating back
to 10 000 BC
• Straw reinforced mud bricks of
ancient times
• Really begins with the advent of
synthetic resins (Bakelite)
during the early part of
twentieth century
• Wood flour or waste string and
rags used as reinforcement to
form the earliest synthetic
composites
• Applications in consumer items
such as radio and speaker cases
Other early biocomposites

• Henry Ford first raised the

possibility of using hemp
fibre reinforced soybean
resin in cars!
• Famous photograph on
the right shows Henry Ford
taking an axe to a
composite panel!
• The body panels of the
Trabant were produced
from cotton reinforced
unsaturated polyester
resin
“Gordon Aerolite”
• Produced by laying up strips of resin impregnated
unbleached flax yarn to form a cross-ply laminate
structure, or unidirectional bar or strip of material
• Heated and pressed to form the composite
• Around 75% by volume was fibre, held together with resin
which formed the remaining 25%
• Ultimate tensile strength and Young’s modulus of
longitudinally loaded material were around 480 MPa and
48 GPa respectively!

Cross-ply laminate
(similar construction to plywood)
Fundamental concepts: phases
(reinforcement, matrix, interface)
and volume fraction
Reinforcement
• Generally much stronger and stiffer than the matrix
• The reinforcement provides the “strength” to the composite
• Reinforcement is often (mainly) in the form of a fibre (glass,
carbon, aramid, boron….)
• Fibres are good in tension (compare with rope), but poor in
compression and shear, therefore need a “matrix” in which
the fibre is embedded to “support” the fibre and to transfer
externally applied loads to the reinforcement
• Fibre geometry as we shall see is important. Fibres may be
“short” (i.e. a defined aspect ratio) or “long” (in effect
infinitely long)
Flax fibre
Reinforcement properties
Fibre type Density Young’s modulus Tensile strength Failure strain
(GPa) (MPa) (%)
(g cm-3)

Synthetic fibres
E-glass 2.56 76 2000 2.6
high strength carbon 1.75 230 3400 3.4

Kevlar™ (aramid) 1.45 130 3000 2.3

boron 2.6 400 4000 1.0
Natural fibres
flax 1.4-1.5 50-70 500-900 1.3-3.3
hemp 1.48 30-60 310-750 2-4
cotton 1.5 6-10 300-600 6-8
cellulose 1.5 135 10000 -
Matrices
• Can be metals, ceramics or, most commonly,
polymers
• Most often weaker and less stiff than the
reinforcement (especially if it is polymer)
• In addition to transferring externally applied loads to
the reinforcement, the matrix protects the
reinforcement from mechanical, physical, chemical
(and biological) degradation, which would lead to a
loss in performance
Some matrix properties (polymers)

Polymer Density Young’s Tensile Failure strain

modulus strength (%)
(g cm-3) (GPa) (MPa)
THERMOSET

epoxy resins 1.1-1.4 3-6 35-100 1-6

polyesters 1.2-1.5 2.0-4.5 40-90 2

THERMOPLASTIC
Nylon 6.6 1.14 1.4-2.8 60-70 40-80

polypropylene 0.9 1.0-1.4 20-40 300

PEEK 1.26-1.32 3.6 170 50

 Interface
• Interface (or “interphase”), transmits the externally applied
loads to the reinforcement via shear stresses at the interface
• The interface is analogous to a glue bond
• If there is no bonding (adhesion) between the matrix and the
reinforcement, then stress transfer will be poor and it will lead
to impaired composite properties
• On the other hand bonding may be too good!
• The interface is therefore a crucial factor in the short and long-
term performance of composites
• Optimising the properties of the interface is a key step in the
development of composites
 Volume fraction
Vf = Vfibre/Vcomposite
Vf = fibre volume fraction
Vfibre = volume of fibre in composite
Vcomposite = volume of composite

• One of the most important concepts in composite science

• The volume fraction of the reinforcement, frequently referred to
as the “fibre volume fraction”, strongly affects many composite
properties
• Varies from a “few” per cent (<10%) to up to around 70% (above
this value, the reinforcement will be in contact and so the matrix
cannot completely surround the reinforcement)
Further reading
• Historical aspect covered in Chapter 14 of ‘Green Composites’
• Callum Hill and Mark Hughes (2010). Natural Fibre Reinforced
Composites: Opportunities and Challenges. Journal of Biobased
Materials and Bioenergy, 4: 1–11
• Faruk, O, Bledzki, AK, Fink, HP and Sain, M. (2012) Biocomposites
reinforced with natural fibers: 2000-2010. Progress in Polymer
Science 37(11): 1552-1596 (DOI:
10.1016/j.progpolymsci.2012.04.003)