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An Introductory Guide
in Industrial PlantsComposites
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Preace
The Queensland Governments Fibre Composites Action Plan New TechnologyTaking Shape launched in April 2006 sets out over 50 initiatives under six theme
areas, ranging rom innovation to skills and training.
The Fibre Composites Action Plan identied the potential or signicant benets
rom increased use o composites in target sectors such as mining, minerals
processing and associated inrastructure.
Deborah Wilson Consulting Services (DWCS) and GHD were engaged to undertake
a study to assess this opportunity and develop approaches that make the choice
o composites in mining applications easier, and more relevant to delivering cost
savings and other benets to industry.
The Queensland Government, through the Department o Employment, Economic
Development and Innovation (DEEDI), unded this study as part o a larger initiativeto help one o the States most promising new industries grow and compete on a
global level.
The aim o the study was to deliver:
case studies on successul use o composites in the mining industry and the
benets composites deliver
business case inormation on the use o composites in dierent applications in
mining, minerals processing and associated inrastructure
inormation covering availability, technical guides and benets o using
composites in common applications in the mining industry
improved links between composites suppliers, manuacturers and the mining
industry to better respond to mining industry needs
inormation kits, presentations and technical seminars on the ndings and
applications where composites deliver value to the mining industry
a model or the composites industry to use in proling valuable applications or
composites in other industries.
This introductory guide addresses a number o these aims. It has been prepared
ollowing a review o relevant technical literature and discussions with the
composites industry.
Disclaimer
This publication was unded by the
Queensland Government (through the
Department o Employment, Economic
Development and Innovation). It is
distributed by the Queensland Government
as an inormation source only. The State
o Queensland makes no statements,
representations, or warranties about
the accuracy or completeness o, and
you should not rely on, any inormation
contained in this publication.
Readers should not act or rely upon anyinormation contained in this publication
without taking appropriate proessional
advice relating to their particular
circumstances.
The Queensland Government disclaims all
responsibility and all liability (including
without limitation, liability in negligence)
or all expenses, losses, damages and
costs you might incur as a result o the
inormation being inaccurate or incomplete
in any way, and or any reason.
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in Industrial Plants
Composites
An Introductory Guide
7/30/2019 Composites in Industrial Plants Pt1
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Table o contents
1. Introduction ___________________________________ 3
2. Overv iew o materials and products _______________ 4
2.1 Qualitative comparison o materials___________ 4
2.2 Benets o composites ______________________ 5
2.3 Product applications________________________ 6
2.3.1 Current applications _____________________ 6
2.3.2 Future applications ______________________ 7
2.3.3 Pipes and ducts _________________________ 7
2.3.4 Tanks and process vessels ________________ 8
2.3.5 Launders _______________________________ 9
2.3.6 Joints and ttings________________________ 9
2.3.7 Coatings and linings ____________________ 10
3. Composite product manuacturing_______________ 11
3.1 Components______________________________ 11
3.2 Fibre reinorcement ________________________ 11
3.3 Resins ___________________________________ 13
3.4 Additives ________________________________ 14
3.5 Cores____________________________________ 14
3.6 Example o a composite laminate ____________ 15
3.7 Manuacturing processes___________________ 15
3.8 Manuacturers ____________________________ 15
4. Australian case stories _________________________ 16
5. Technical perormance _________________________ 18
5.1 Design___________________________________ 18
5.2 Standards________________________________ 18
5.3 Guides __________________________________ 19
5.4 Relative perormance o materials ___________ 19
5.5 Service lie _______________________________ 20
5.6 Mechanical properties _____________________ 20
5.6.1 General _______________________________ 20
5.6.2 Strength ______________________________ 20
5.6.3 Fatigue________________________________ 21
5.6.4 Creep _________________________________ 22
5.6.5 Abrasion resistance_____________________ 22
5.7 Thermal properties ________________________ 22
5.8 Chemical properties _______________________ 23
5.9 Electrical properties _______________________ 265.10 Perormance o composites in re____________ 26
5.11 UV resistance_____________________________ 27
5.12 Working with composites on site_____________ 28
5.13 Inspection and testing _____________________ 28
6. Economic comparison__________________________ 30
7. Environmental comparison _____________________ 31
8. Reerences ___________________________________ 32
9. Australian manuacturers o composite
industrial products ____________________________ 34
10. Australian composites design and
engineering service providers ___________________ 41
11. Acknowledgements____________________________ 43
List o abbreviations
ACI American Concrete Institute
AS Australian Standard
BS British Standard
CFRP Carbon Fibre Reinorced Plastic
CTE Coecient o Thermal Expansion
F RP F ibre Reinorced Plastic
GRP Glass Reinorced Plastic
HDT Heat Distortion Temperature
ISO International Standards Organisation
PTFE Polytetrafuorethylene
PVC Polyvinyl Chloride
PVDF Polyvinylidene Fluoride
UV Ultraviolet (sunlight)
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1 Introduction
A composite is a material made up o two or more components so the benecialproperties o each component are utilised. In this guide, composite reers to a
material composed o a thermosetting resin and bre reinorcement. Composites
are also reerred to as breglass, glass reinorced plastic (GRP), bre reinorced
plastic (FRP) and carbon bre reinorced plastic (CFRP). As there are many dierent
resins, reinorcements and methods o putting the two together, there are a
multitude o materials which can be described as composites.
Composites oer unique products in many o Queenslands most important
industry sectors, including advanced manuacturing, aerospace, building and
construction, deence, inrastructure, marine, mining and transport. As composites
are light-weight and corrosion-resistant, the materials have the potential to reduce
costs, save time and provide a saer work environment. At a time o fuctuating
steel prices and long delivery times, composites oer a real alternative to reducecapital and operational costs, and downtime. Composites light-weight nature
provides operational savings or trucks and mobile equipment, and their
corrosion-resistance prevents the hazards o rusting steel structures.
Composites have been used in many Australian industries since the 1940s. For
example, in the minerals processing and chemical industries, the materials are
used in a variety o applications including tanks, pipes, process vessels and foor
grating. In the mining industry, the materials are used in applications including
ducts, truck bodies and rock bolts. It seems the Bronze Age and Iron Age have
passed, and the composites age is now upon us.
The Queensland Government is capitalising on Queenslands strengths as a world
leader in the research, development and commercialisation o bre composites
technologies through the implementation o its Fibre Composites Action Plan, andsignicant investment under the Smart Futures Fund.
For more inormation on Queenslands Fibre Composites industry please visit:
www.composites.industry.qld.gov.au
Lucy Cranitch, GHD, produced this guide. It aims to provide an introduction to
composites in the mining, mineral processing and chemical industries, and to
assist in the decision to purchase a composite component. It does not provide
design details o composite components.
For more inormation on GHD please visit www.ghd.com.au
A composite is a material
made up o two or more
components so the benecial
properties o eachcomponent are utilised.
Carbon bre-epoxy drill rod prototype
with embedded strain gauges and carbon
nanotube-epoxy threads
Image courtesy of Teakle Composites
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2 Overview o materials and products
2.1 Qualitativecomparisonofmaterials
The table below provides a quick comparison o materials.
Table 1 Qualitative comparison o materials
Material Advantages Disadvantages
Mild steel High strength
High stiness
High ductility
Susceptibility to corrosion
Susceptibility to atigue
High weight
High energy required or production
Stainless steel Corrosion resistance High cost
Aluminium Low weight
High ductility
Ease o recycling
Susceptibility to corrosion in strong acids and alkalis
High energy required or production
Plastic (polyethylene,
polypropylene, polyvinyl
chloride (PVC), etc)
Corrosion resistance
Low cost
Low coecient o riction
Ease o recycling
Susceptibility to creep
Low stiness
Non-conductive properties can be a disadvantage
Limited temperature resistance above 200C
Composite Corrosion resistance
Low weight
High strengthConductivity or non-conductivity
Low coecient o riction
Limited temperature resistance above 250C
Sensitivity to impact damage
Wagners Composite Fibre 100 x 100 mm
pultruded sections
Image courtesy of
Wagners CFT Manufacturing Pty Ltd
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2.2 Benetsofcomposites
Corrosion resistant
With the selection o correct materials, composites will not deteriorate in acids,alkalis, solvents and salt water, and can be used rom pH 0 to 14. Composites are
thereore used widely in tanks, pipes and process vessels in chemical extraction
o base and precious metals. Plant operating time can thereore be maximised.
Both minerals processing and chemical plants use this durable material or plant
inrastructure, such as gratings and hand rails, where rusting o steel structures
can place the saety o plant personnel at risk. Since composites do not require
painting, there are also reduced maintenance costs.
Durable
Composite materials are durable due to their high strength and high resistance
to atigue, abrasion and creep. Agitated tanks made rom composites have been
ound to operate successully or many years despite the cyclic loads experienced.
In pipelines, resistance to abrasion combined with a low coecient o riction aidsprocess fow and reduces downtime. This overall durability o composites reduces
the need or maintenance and repair, which maximises plant running time.
Light in weight
Composites are relatively light in weight compared to steel, iron and concrete.
For example, typical composite pipes are approximately 25 per cent o the weight
o ductile iron and 2 per cent o concrete equivalent pipe mass per metre. The
reduced weight o composite pipes, tanks and process vessels has led to lower
transportation and installation costs or the mining industry, and reduced plant
downtime through enabling installation at sites where access is restricted. Where
electrical guarding and hatches need to be lited by plant operators, the composite
option at less than 10 kg per sheet is certainly preerable to the steel option at
more than 20 kg. This also applies to hatches and all components that must belited to ensure the saety o all personnel.
Electrically insulating or conductive
For saety reasons, the electrical insulation o process equipment is critical
where high electric currents or voltages are used. Composites that are electrically
insulating are used in high electric currents or voltage environments, such as pot
rooms in aluminium processing and in electrowinning. The radio and magnetic
transparency o composites is useul in a number o applications. In applications
where static charge can build-up, static dissipation and grounding o equipment
is critical to keep plants operating and to prevent res where fammable solvents
are used. Conductive properties can also be built into the composite equipment or
applications such as solvent extraction.
Thermally insulating
Where high temperature fuids are stored in vessels or pipes, thermal insulation
is critical or saety. The use o composites in these applications can reduce or
eliminate the need or insulation with external temperatures typically being less
than 60C or fuids and liquors up to 100C. Furthermore, being an insulator, the
transer o heat rom composite materials to any body part is very much less than
that rom a conductive material such as stainless steel.
Flexible in design and manufacture
Composite materials oer solutions to many manuacturing problems due to the
vast array o resins, reinorcements and unique manuacturing methods used
to produce them. Such fexibility in design and manuacture can result in cost
and time savings. For example, it is relatively simple or composite materials to
create compound curves in metallic materials. Also, while large covers usually
require large support structures, the light weight nature o composites means it is
possible to design covers that are supported on the edge o a vessel without the
requirement or intermediate supports. Composites manuacturing processes,
such as hand lay up, also enable unique designs to be manuactured at relatively
All FRP (handrails, stair treads, landing
and support structure) stair platorm
Image courtesy of Exel Composites
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low cost. The ability o composites to conorm to any shape and bond with steel
and concrete enables rehabilitation and retrot. For example, composite materials
are well used in the lining o process vessels. Composite materials fexibility in
design and manuacture also means on-site manuacture o very large vessels,
such as lament winding o large tanks, is possible
2.3 Productapplications
2.3.1 Current applicat ions
Composites can be used in many applications in the mining and process
industries, including:
Mining
ducts or ventilation, chilling and cooling in underground operations
cuttable rock bolts (used in reinorcement), rib bolts and brackets
mobile and stationery containers or water, diesel and other liquid
storage on site
bore casings and insulation in underground structures
theodolites and legs or survey equipment.
Mineral and chemical processing
tanks or storage o corrosive and non-corrosive materials
process vessels including gas cooler condensers, electrostatic mist
precipitators, leach tanks, reactor tanks, thickeners, electrolytic cells, cell
bearers, mixer settlers, spent tanks, cr ystallisers, solvent ext raction and
electrowinning cells, and pulse columns
mineral sands separation equipment including spirals, cone concentrators
and hydrocyclones
cooling towers
linings or concrete and steel tanks and equipment
claustra walls and panels
ans, blades, bafes, agitators, bottom scrapers and mixing tools
pipes, ttings and launders including products or abrasive (e.g. slurry)
and non-abrasive materials
nozzles, fanges, elbows, reducers, branches, tees and joints
ducts or transporting process gases and ume extraction
scrubbers and waste gas towers, quench towers and demisters
dampeners/valves
gratings, ladders, walkways, handrails, steps and platorms
inspection hatches, hoods and covers
structural applications such as support beams, channels and angles
roth crowders or fotation tanks
protective guards on machines
consoles
telescopic handles or sampling and testing
stacks, fues and other large structures
use o composites to repair ailed plant components.
Chemical resistant FRP piping system
with coupling or use in highly
corrosive environments
Image courtesy of A.C.Whalan Composites
The ability o composites
to conorm to any shape
and bond with steel
and concrete enablesrehabilitation and retrot.
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Mine site inrastructure
guards, grating, walkways, platorms, kick rails, stairs and ladders
rebar and stay-in-place ormwork or concrete
polymer concrete
concrete foor and bund coatings and lining
cable supports, trays and ladders
pumps
power poles including cross-arms
wall and roo sheeting as well as purlins in site buildings
window and door rames
water treatment and supply
bridges
trusses
manhole covers
railway sleepers
drains and sumps
poles to remove high voltage lines.
Port inrastructure
guards and inspection hatches
gratings, ladders, walkways, handrails, steps and platorms
structural panelling, sheet piling and other applications in marine environments.
2.3.2 Future applications
The advantages o composites described above have led to investigations intonew applications or composites, including:
truck bodies, cabs, panels and engine casings (ully breglass cabs have been
used by Leader trucks and Mack trucks since the 1970s)
access ladders, hand rails and steps attached to major mining and
earth moving equipment
wear blocks
long and short conveyors including supports, covers and hoods, guards
and rollers
wash plant pipes and air receivers
port loading inrastructure
gag ducts or re suppression in underground mines.
2.3.3 Pipes and ducts
From pipes carrying sulphuric acid in leaching o copper bearing ore, to waste
water, composite pipes have widespread use in the chemical and minerals
processing industries in Australia. Key benets include resistance to corrosion
in chemical environments, increased hydraulic fow and reduced operating costs
through comparatively low riction compared to steel. Conductive composite
pipes are much saer than plastic pipes in solvent extraction plants, and have
been ound to be more cost eective and durable than the alternative SAF2507
stainless steel.
21 mm solid FRP rods supplied to customer
as concrete rebar to eliminate any
electrostatic intererence with its equipment
Image courtesy of Exel Composites
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In underground mining, composite ducts are used or ventilation as its light weight
nature enables much easier installation and lighter supports than other products.
In the chemical and minerals processing industries, composite ducts are used or
applications like transporting sulphur dioxide in plants manuacturing sulphuric
acid, and in minerals processing plants to extract umes.
There are a range o standards and guidelines available or the design and
manuacture o composite ducts and pipes. Those most widely used in
Australia include:
Composite pipes can be used at low and high pressures. For example, the API 15
HR specication or high pressure breglass line pipe covers pipes rated or
3.45 MPa to 34.5 MPa.
For above ground pipes and ducts, BS 6464 contains inormation on installation
including supports, guides and anchors. Pipe support spacing is important and the
ratio o the vertical defection o a pipe to the horizontal span between supports
is oten limited to 1:300. For pipe supports, a minimum contact arc o 120 under
the pipe is typical and rubber packers between the support and the pipe can help
reduce point loads.
For buried pipes, AWWA C950 contains inormation on design whilst AS 2566
and BS 6464 can be used or installation. Inormation on trench preparation,
backlling material and installation procedures are given in these standards.
It is possible to make continuous radius bends, including elbows and long radius
bends, as a single unit with no longitudinal joints in composites.
2.3.4 Tanks and process vessels
In the chemical and minerals processing industries, composite tanks and process
vessels have a long history o successul use in chemical environments which
readily corrode steel and attack concrete.
Sulphuric and hydrochloric acids are widely used in processing copper, lead, nickel
and zinc. In these manuacturing plants, composites are used to construct leach
tanks, thickeners, electrolytic cells mixer settlers, spent tanks and pulse columns.In sulphuric acid manuacturing plants, composites are widely used in radial fow
scrubbers, gas cooler condensers and electrostatic mist precipitators.
AS 3571 Plastics piping systemsGlass-reinorced thermoplastics (GRP) systems based on unsaturated
polyester (UP) resinpressure and non-pressure drainage and sewerage; and pressure and non-
pressure water supply
AS 2634 (obsolescent) Chemical plant equipment made rom glass-bre reinorced plastic (GRP), based on thermosetting
resins
AS/NZS 2566 Buried fexible pipelines
BS 7159 Code o practice or design and construction o glass-reinorced plastics (GRP) piping systems or
individual plants or sites
BS 6464 Specication or reinorced plastic pipes, ttings and joints or process plants
BS EN ISO 14692 Petroleum and natural gas industriesglass-reinorced plastics (GRP) piping
ISO 10467 Plastics piping systems or pressure and non-pressure drainage and sewerageglass-reinorced
thermosetting plastics (GRP) systems based on unsaturated polyester (UP) resin
ISO 10639 Plastics piping systems or pressure and non-pressure water supplyglass-reinorced
thermosetting plastics (GRP) systems based on unsaturated polyester (UP) resin
ANSI/AWWA C950 Standard or berglass pressure pipe
ISO 10639 Plastics piping systems or pressure and non-pressure water supply using GRP systems based on
unsaturated polyester (UP) resin.
FRP Fuel tanks
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While the corrosion resistance o composites is a key benet, the relatively low
cost o composites compared to alternative materials such as stainless steel,
duplex and other alloys has also accelerated their acceptance.
The ollowing standards and guides are applicable to composite tanks and vessels:
As well as storage tanks and process vessels, composites can also make internal
components such as bafes and weirs. For example, composite fanges, manways
and other xtures can be built into the composite tank or vessel.
It is important to reinorce areas o composite tanks and vessels subject to higher
loads. Shells should be reinorced with external circumerential reinorcing ribs
to provide rigidity, particularly where agitators are not independently supported.
Floors should be reinorced where intermediate supports are needed or tank
roos. Roos should be reinorced where personnel and/or other equipment need to
be supported.
Inormation on supports or tanks and process vessels is given in the standards.
It is standard practice to use concrete slabs as supports, however, concrete ring
beams lled with compacted sand nished with a layer o sand and oil mixture can
also be used.
2.3.5 Launders
There is no design standard specically or composite launders, although BS 6464
contains some applicable inormation. The stiness o the launder should be
sucient to prevent sag, twist, camber or spreading without ull length supports or
restraints while the launder is operating. It is advisable to reinorce o-take areas
o launders.
2.3.6 Joints and fttings
The type o joints aects the durability and cost o pipelines. Common methods
o joining composite pipes are butt and strap; rubber ring type and fanged joins.Restrained joints eliminate the need or and thus cost o thrust blocks etc. Butt
and strap joints used with composite pipes are restrained, have similar chemical
resistance to the parent pipe material and are less susceptible to leaks. However,
in terms o installation butt and strap joints are slow and costly and do not tolerate
misalignment or movement well. Whilst rubber ring type joints are not restrained,
they are quick to install and tolerate some degree o misalignment and movement.
Thus rubber ring type joints are particularly useul or buried pipelines.
There are a number o requirements or durable butt and strap joints. The strength
o the joint must be at least equivalent to that o the parent material. The required
widths o pipe joints are given in the standards, and where accessible, the internal
surace o the joint should be laminated. Since joints are hand laid, their thickness
must be that o a hand laid pipe, even or joints in a lament wound pipe. To
prevent ingress o fuids into the laminate, all cut ends must be sealed with resin.
Tees, branches and other similar joints can be prepared using similar techniques
to those employed or standard composite butt and strap joints.
AS 2634 (obsolescent) Chemical plant equipment made rom glass-bre reinorced plastic (GRP), based on
thermosetting resins
BS 4994 (superseded) Specication or design and construction o vessels and tanks in reinorced plastics
BS EN 13121 GRP tanks and vessels or use above ground. Design and workmanship
BS EN 13923 Filament-wound FRP pressure vessels. Materials, design, manuacturing and testing
ASME RTP-1 Reinorced thermoset plastic corrosion resistant equipment
ASTM D3299 Standard specication or lament-wound glass-ber-reinorced thermoset resin
corrosion-resistant tanks.
FRP fange installed at a ertilizer (phosphates)
manuacturing acility in Australia
Image courtesy of Lucy Cranitch, GHD
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Flanged joints are also widely used and fanges can be made rom composite
materials. The thicknesses o composite fanges depend on the design, but are
generally greater than that o metal fanges. ANSI dimensions are commonly used
or bolt patterns, and composite fanges can be manuactured to be compatible
with most existing fanges made o PVC, steel and ductile iron. It is important
to ensure composite fanges are fat to provide a good seal, so ull fat-aced
fanges with steel backing rings are oten used. It is important to never mix ull
ace composite fanges and raised ace fanges as this readily results in leaks and
ailures. To avoid point loads caused by nuts directly in contact with the composite
fange ace, washers should be used under nuts, relies can be cut into the ace o
the fange and care must be taken with bolt torque. All cut outs or bolt holes must
be sealed with resin to enhance durability. A number o standards are applicable
to fanges.
2.3.7 Coatings and linings
Composites can be used in conjunction with concrete or steel to provide a
corrosion-resistant lining or coating. This may be in the orm o an internal
corrosion protection to steel or concrete tanks, or as a protective layer on concrete
foors or bunds. The ollowing standards and guides are applicable to composite
coatings and linings:
The ollowing steps are typical in applying a bonded composite layer to concrete:
1. The concrete should be let 28 days to cure prior to application o any coating
or lining.
2. Surace preparation o the substrate is important. Abrasive grit blasting (high
pressure water or grit blasting) o the surace is required to improve bonding
o the coating or lining.
3. Remove dust or grit by vacuuming and/or sweeping.
4. Wash the surace to remove oils, greases and other contaminants.
5. Dry the substrate.
6. Test or suitability o the coating or lining. Various tests are required
depending on the substrate, or example pH, moisture and surace pull-o
tests are required or concrete.
7. Fill voids with a resin-based ller.
8. Prime.
9. Apply the basecoat, consisting o resin reinorced with bre mats or
with llers.
10. Apply the top coat, and i required spread silica aggregate to provide
slip resistance.
Quality control during the coating or lining process is important. This should
include wet lm thickness tests, adhesion tests, coating sensitivity tests and resin
gel time tests. I an additional conductive primer coat is applied, spark testing can
be conducted once the basecoat is applied.
BS 6374-4 Lining o equipment with polymeric materials or the process industries. Part 4: Specication or lining
with cold curing thermosetting resins
ACI 515.1R Guide to the use o waterproong, damp-proong, protection and decorative barrier systems or concrete.
AS 4087 Metallic fanges or waterworks purposes
AS 2129 Flanges or pipes, valves and ttings
AS 4331.1 (ISO 7005) Metallic fanges (steel fanges)
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3 Composite product manuacturing
3.1 Components
Each component contributes to the overall properties, perormance and
appearance o the composite product. The precise type o materials and
manuacturing process used are determined by the specic properties required
or the nal product. The ollowing principles are essential or the production
o good-quality composite products:
quality o materialsresins, glass bres, additives and cores
quality o designquantity, orientation and suitability o bres, suitability and
volume o resins, suitability and volume o additives, and suitability o cores
quality o manuacturingconsistency and control o the manuacturing and
curing processes. Full curing o the product is essential to attain optimum
mechanical properties, prevent heat sotening, limit creep and reduce fuiddiusion
quality o transport and installation practices.
As the composite material itsel is made at the same time as the part, quality
assurance and inspection throughout these processes are essential.
3.2 Fibrereinforcement
The role o the reinorcement in a composite part is to carry the applied load.
The actors which aect the contribution o the reinorcement to the composite
properties are:
the type o reinorcement
the orm o reinorcement
the quantity o reinorcement (resin-to-reinorcement ratio)
the orientation o the reinorcement.
Type: Many dierent types o reinorcement are available, including E glass,
ECR glass, C glass, carbon, aramid (Kevlar) and many other less common bres.
Carbon bre is used in the mining industry primarily to provide conductivity.
The bulk o the reinorcements are made o glass. E glass is the most widely
used bre type due to its high strength and relatively low cost. C glass is used
where excellent chemical resistance is required, usually in the orm o a tissue
as described in the table below. ECR glass is sometimes used to provide better
resistance to chemicals.
The ollowing table, taken rom the Eurocomp Design Code, compares typical glassbre properties. Compared to steel, glass bres have approximately 2.5 times the
strength with only one third o the density, and higher dimensional stability.
Table 2 Comparison o properties o glass fbre types and steel
Composite products consist
o a combination o bres,
resins, additives, and in
some cases, cores.
Fibreglass borehole liner
Image courtesy of Teakle Composites
Property Eglass Cglass Steel
Specic gravity 2.54 2.50 7.8
Tensile strength (MPa) 3400 3000 1350
Tensile modulus (GPa) 72 69 200
Elongation (%) 4.8 4.8 1032
Coecient o thermal expansion (106/C) 5.0 7.2 11.5
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Form: Fibres are available in many orms, as described in the ollowing table.
Table 3 Forms o reinorcement
Quantity: The manuacturing process has a large eect on the quantity o
reinorcement in composites. Fabrics with closely packed bres will give a higher
volume raction o reinorcement than those abrics with large gaps between bre
bundles. The weight per unit area o reinorcement varies greatly rom as low as
20 g/m2 or tissues, to 300 or 450 g/m2 or chopped strand mat, to 800 g/m2
or woven rovings, and to well over 1600 g/m2 or lament wound rovings. As a
general rule, the strength and stiness o a composite are proportionate to the
quantity o reinorcement present. However, the laminate strength peaks at an
optimum bre volume o about 70 per cent, above which the strength declines due
to a lack o resin to hold the bres together.
Orientation: The tensile strength o bres is greatest in longitudinal directionrather than width. Fibres must thereore be oriented in the direction o the load,
and orientation can be designed to suit the particular loading requirements o the
Reinforcementform Description
F ilament Individual bres as initially drawn rom the raw materials. F ilaments are processed ur ther
beore use.
Continuous strand Filaments gathered in continuous bundle. Continuous strands are processed urther
beore use.
Milled bre Continuous strands hammer-milled into lengths o 0.8 to 3 mm. Milled bres are used as
llers and additives to control heat distortion and improve surace quality in compounding
and casting.
Chopped strand Strands chopped to 5 to 60 mm leng ths.
Roving Strands bundled together without twist. Rovings are used in various manuacturing processes
including lament winding and pultrusion to give high strength in the direction o the bres.
Yarn Twisted strands. Yarns are processed urther beore use such as in the manuacture o cloths.
Chopped strand mat Non-woven mat o chopped strands in random orientations. This reinorcement is widely used
to give strength in all directions and good inter-laminar adhesion.
Continuous strand mat Non-woven mat o continuous strands in random orientations.
Tissue/veil Fine non-woven mat o continuous laments that are uniormly distr ibuted over the surace
in random orientations. Tissues have relatively low strength. Their purpose is to support a
resin-rich layer which protects the composite rom moisture and chemicals, through preventing
these fuids entering the laminate along the bres.
Unidirectional abric Rovings in one direction held together by a small amount o bres woven or stitched at 90.
Unidirectional abrics give strength in one direction.
Woven roving Rovings woven into a abric in a particular pattern, usually a plain weave. Woven rovings give
strength in two directions.
Cloth Fabric made rom yarns woven in a par ticular pat tern. Cloths give streng th predominantly in
two directions.
Stitched abric Layers o bres held together by stitching. Stitched abrics give strength predominantly in two
directions and have higher interlaminar strength than cloths.
Multi axial abrics Fabric made rom yarns or rovings in more than two directions. Multi axial abrics give strength
in three or more directions.
Needle punched and
combi-mats
Fibreglass cloth composed
in a swirl pattern
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part. Unidirectional bres run in one direction only, whereas abrics have bres in
predominantly two directions, and chopped strands are oriented in all directions.
The combination o reinorcements results in an anisotropic material, where its
properties vary with direction.
3.3 Resins
While the bres are the principal load-carrying members, the surrounding matrix
o resin maintains them in the desired orientation and location. It also allows
the applied load to be transerred between the reinorcing bres. Another very
important unction o the resin is to provide a barrier to the environment, which
protects the composite rom the elements, such as water and chemicals.
Resins are also reerred to as polymers as they are made up o many (poly)
long-chain molecules (mers). It is helpul to distinguish between two broad groups
o polymersthermoplastic and thermosetting. Thermoplastic polymers melt
when heat is applied. This is because their long chains are not chemically bound
together (i.e. they are not cross-linked). Thermosetting polymers, on the other
hand, do not melt when heated because their long chains are chemically bound
together (i.e. they are cross-linked). The resins used in composites (and those
described here) are all thermosetting polymers.
There are a great variety o resins. The most common groups are polyester, vinyl
ester and epoxy. Whilst re retardant versions o these resins are available,
phenolic resins are also used in situations where re retardant properties are
required. Resins are supplied to composite manuacturers in a liquid state, and
during the manuacture o the composite part the resin is cured to orm a solid.
This process o curing the resin is a chemical reaction in which the cross-links are
ormed between the polymer chains. Beore curing, the resin is in a liquid state as
the polymer chains can fow easily. Once the polymer chains are linked together,
the polymer chains can no longer fow and the resin becomes a hard solid.
Polyester and vinyl ester resins supplied to the composite industry are dissolved
in styrene monomer. This reduces the viscosity, so that the resin fows more readily
to allow ease o spreading and ensures ull bre-wetting, complete impregnation
and minimal voids. The styrene monomer is also a key component in the curing
process o polyester and vinyl ester resins, orming the cross-links between the
polymer chains.
Polyesterresins provide good strength at a relatively low cost and are used widely
in the marine industry, and in pools, spas, transport, casting, inrastructure and
automotive applications. Various types o polyester resins provide a wide variety
o properties relating to water and chemical resistance, weathering and shrinkage
during curing.
Vinylesterresins are used primarily where improved water and chemical
resistance, heat resistance or improved fexibility is required. Standard and
high perormance vinyl ester resins are widely used in the mining and chemical
industries due to their high resistance to acids, alkalis and solvents.
Epoxyresins have a dierent structure to polyester and vinyl ester resins. They are
usually sold as a two-pack systemPart A and Part B and these two parts must be
mixed strictly in the ratios given by the supplier. The part A is the resin and the part
B is the hardener and there are a number o dierent types o each. Epoxy resins
are not dissolved in styrene monomer and do not shrink as much as polyester or
vinyl ester resins when they cure.
Epoxy Resins provide particularly good mechanical strength and adhesion and
have good stiness, toughness, heat resistance and water resistance. Epoxy resins
tend to be more expensive than polyester resins. Epoxy resins are widely used in
piping and inrastructure.
It is helpul to distinguish
between two broad groups
o polymersthermoplastic
and thermosetting.
Spent Electrolyte Tank installed at
Cause Nickel, Kalgoorlie
Image courtesy of Marky Industries Pty Ltd
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3.4 Additives
The ollowing additives can be incorporated into the resin:
Fillers are powders used to add bulk to the resin, which reduces costs and
enhances the compressive strength o the composite material. Fillers can also
reduce the exotherm (heat build-up) and shrinkage during curing. Fillers may be
added to the resin at up to 50 per cent by weight (or dense llers) or 35 per cent by
volume. Addition o ller over these amounts should be avoided as it reduces the
fexural and tensile strengths, as well as the chemical resistance o the composite.
Thixotropes are powders added to the resin to allow it to hold up onto a vertical
surace. The addition o thixotropes is required when the resin must not run or
sag when it is applied to steep moulds or to vertical walls (such a lining o a tank).
Thixotropes allow the resin to fow when a shear orce is applied (i.e. when resin
is orced through a spray gun), and prevent the resin rom fowing when the orce
is removed.
Pigments can be incorporated into the resin to produce a specic colour and to
provide UV resistance.
UVinhibitorsandabsorbers can be added to the resin to improve its UV resistance.
Flameretardants can be added to the resin to improve its resistance to re.
Inhibitors are chemicals added to the resin to slow down the curing reaction, so
more time is available to work with the resin during manuacture beore it cures.
As resins can cure in storage, inhibitors help to extend the resins storage lie.
Promotersandaccelerators are chemicals added to the resin to speed up the
curing reaction to enable manuacture in a reasonable timerame.
While additives improve many properties o composites, they can also impair other
properties at the same time. For example, some re retardants can reduce thecomposites resistance to weathering and chemicals. Additives should thereore
be careully selected.
3.5 Cores
Some composite parts incorporate core materials, primarily to impart stiness
without increasing weight. Cores may also be used to increase the impact strength,
atigue resistance, thermal insulation and sound deadening eect. For a panel, the
fexural stiness is proportional to its thickness cubed, which means as thickness
increases, stiness increases dramatically. Cores can be used in specic areas o
a structure where extra stiness is required (e.g. stiening ribs) or throughout the
area o a laminate as a sandwich panel.
A sandwich panel consists o a core with reinorcement and resin on either side(skin). In a sandwich panel, the adhesive layers between the skins and the core
must be able to transer the loads and thereore be at least as strong as the core
material. Without a good bond, the three components work as separate beams
and the stiness is lost.
Figure 1 shows a sandwich panel under a bending load. As a result o the bending,
the upper section is placed under compression, the lower section in tension and
the core in shear. Shear strength and stiness o a core material are important.
Fibreglass drill rod joint assembly
in Instron testing machine
Image courtesy of Teakle Composites
Figure 1. Bending a sandwich panel
Compression
Shear
Tension
Skin
Core
Skin
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3.6 Exampleofacompositelaminate
Figure 2 shows the wall o a composite tank or pipe to illustrate the
layers that make up the composite material.
The reinorcement sequence is oten given on drawings in the
ormat below, in order rom the internal surace to the outer surace:
C/2M/4(MW)/M/C*
Reinorcements:
C = 40 g/m2 C glass or synthetic tissue such as Nexus tissue.
M = 450 g/m2 E glass powder bound chopped strand mat.
W = 800 g/m2 E glass woven roving.
C* = 40 g/m2 C glass or synthetic tissue such as Nexus tissue with
resin containing wax and UV inhibitors or pigment.
3.7 Manufacturingprocesses
Formation o a composite product involves combining layers o reinorcement withresin. A chemical reaction o the resin then converts it rom a liquid to a solid to
bind everything together as a whole. This chemical reaction is called curing, and is
activated by catalysts or polyester and vinyl ester resin and a hardener or epoxy
resins. The catalyst or hardener must be added to the resin prior to combining the
resin with the reinorcement. It is important to achieve good cure o resins in a
timely manner. This can be achieved through adjusting the chemicals involved in
curing, including the inhibitors, accelerators and catalyst or hardener, and through
taking account o the temperature during manuacture. There are a number o
dierent manuacturing processes.
Handlayupinvolves the manuacture o a part in a mould. Resin is rst applied to
the mould surace, then layers o glass which are wet by the resin and consolidated
with rollers.
VacuumInfusionProcessing(VIP) involves the lay up o dry glass on a mould. A
fexible lm (bag) is then laid over the glass and sealed to airtight and then the
resin is pulled through the glass under the orce o a vacuum.
ResinTransferMoulding(RTM) uses two matched moulds a bottom mould and a
top mould. This process thereore produces parts with two nished suraces.
Filamentwindingis perormed on a machine that winds glass bres onto a
cylindrical mandrel in a prescribed pattern to orm the desired nished shape (e.g.
a pipe). Fibres in the orm o continuous rovings are routed through a bath o resin
beore reaching the mandrel. Ater curing, the tube is removed rom the mandrel.
Pultrusion is used or the manuacture o products o a constant cross-section.
The glass bres are pulled through a die (as compared to extrusion where thematerial is orced through a die) in a continuous process, injected with resin,
shaped by the die and then cured.
3.8 Manufacturers
Australias composites industry is represented by Composites Australia Inc.
Composites Australia is a membership-based, not-or-proft association dedicated to
increasing the awareness and general usage o composites in Australia. Composites
Australia has access to an extensive database o organisations in the Australian
composites industry including raw material suppliers, manuacturers, designers
and engineers, research and development agencies and training and education
providers. See section 9 o this guide or contact details or a number o Australian
composite product manuacturers, or contact Composites Australia at:
Level 15, 10 Queens Road, Melbourne Victoria 3004
Telephone: + 61 3 9866 5586 or 1300 654 254
Facsimile + 61 3 9866 6434
www.compositesaustralia.com.au
Figure 2. An example o the makeup o a composite wall
C = Tissue
M = Chopped Strand Mat
W = Woven Roving
Alternating chopped mat& woven roving to desired
thickness
Vinyl Ester Resin resin/waxtopcoat
C M M W M M M M M C
Primarycorrosion
barrier
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4 Australian case stories
The ollowing tables provide examples o where composites have been usedin Australia.
Table 4 Current composite components in Australian mining and minerals
processing plants
Enduser Industry Location Components
Rio Tinto Aluminium Gladstone, QLD Hoods or ume tanks, pipes, claustra walls in pot rooms
Adelaide Chemical
Company
Copper Burra, WA Acid leach tanks (agitated), tank, slurr y pipe, grating, gas
cooling tower
Xstrata Copper
Reneries
Copper Townsville, QLD Electrolyte pipework, polymer concrete Electrolytic cells,
galvanizing tank, acid storage tank, grating, wall cladding,
roong
BHP Billiton,
Olympic Dam
Copper,
uranium,
gold, silver
Roxby Downs, SA Mixer settlers, Jameson cells, pipes in solvent extraction and
electrowinning, bund linings, ducts, electrolytic cells, stack,
tanks, electrostatic mist precipitators
Kanowna Belle Gold Gold WA Roaster stack, an to stack ducting
Posgold Ltd Gold WA Tanks
Nystar Lead Port Pirie, SA Roo and wall sheeting, cable ladder to support cabling
Heraeus Ltd Metals VIC Fume extraction ducting or precious metals recovery plant
Rennison Mine Mining Burraga, NSW Pump
Centaur Mining
Minproc/Davy
JV Cawse Nickel
Nickel WA Settler tank and lids
Kombalda Nickel Smelter Nickel WA Process equipment in the sulphuric acid plant
Kalgoorlie Nickel Smelter Nickel Kalgoorlie, WA Electrostatic mist precipitators, scrubber
BHP Billiton, QNI Nickel Yabulu, QLD Leach tanks, linings in the stage 2 organic running tank and
the cobalt sulphate discharge storage tank, lining o gas
cooler condensers
Sunmetals Zinc Townsville, QLD Cooling towers, grating
Xstrata Zinc and lead Mt Isa, QLD Froth crowders or fotation tanks
Nyrstar Zinc Hobart, TAS Leach reactor tanks and wash down tanks, electrolytic
cells, spent tanks, launders, cooling towers, tank covers,
cell bearer, bafes or tank, copper sulphate reactor tanks,
mercury removal towers, oreshore stacks, pipework,
precipitators, concrete tank linings, tanks, agitator blades,
segmented clarier covers, tank, dampeners, butterfy valve,
gas cooling towers and internals.
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Table 5 Current composite components in Australian chemical processing plants
EndUser Industry Component
Ferro Corporation Ammonium and
sulphur products
Sieve tray scrubbing tower
Nuarm Chloralkali Plant Chloralkali plants Sodium hypochlorite storage tanks, chlorine headers, chlorine
scrubber, anolyte tank
Incitec Pivot Sulphuric acid and
ertilizer
Settlers, pipes, radial fow scrubber, 2 gas cooling towers, ducts,
drying tower inlet maniold, 8 electrostatic mist precipitators
Alcoa General chemical Tank
Australian Chemical
Company
General chemical Mist eliminator vessel or copper roaster
NSW Brickworks General chemical Freestanding insulated ume stack
Chemplex efuent
treatment plant
General chemical Pipework
Feld Proctor Gamble General chemical Tank
ICI Operations General chemical Tank
Koka Chrome Ind. Co Ltd General chemical Fume extraction ducting or plating plant
Metalok (S) Pte Ltd General chemical Plating line ume exhaust ducting
Pritcorp Sdn Bhd atty
alcohol plant
General chemical HCl vapour scrubber, glycerine reactor/settler, acidulated soap
storage surge tank, tank
SCM Milenium Chemicals General chemical Titanium dioxide stack, chlorine scrubber
Tiwest General chemical Titanium dioxide stack, plant pipework
Toxide Group Services General chemical Ducting (ume extraction), stack (steel supported)
Unizon Singapore General chemical 3600 cm vertical scrubber
Delta (BHP) EMD Plant Manganese dioxide Electrolytic cells, storage tanks or resh and spent electrolyte
Cold Rolling Sdn Bhd Steel Pipe (or pickle line), lining o steel prefux tank, lining o steel acid
pickling tank
Tubemakers Steel Acid pickling tank
BHP Pellet Plant Steel Waste gas tower, ne scrubber, quench tower, ne scrubber demister,
pre-quench scrubber
Minnehasa Sulphuric acid Mercury removal tower.
50 m Composite Fibre Conveyor.
Modulus design or easy transport,
assembly and dismantling.
Capacity: 400 tone per hour
Belt speed: 2 m/sConveyor span: 24 m
Number o spans: 2
Incline angle: 20 degrees
Image courtesy of
Wagners CFT Manufacturing Pty Ltd
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5 Technical perormance
This section is particularly aimed at people who are relatively unamiliar withcomposites, and or those who would not normally have considered them or
applications. This section aims to raise awareness o the properties o composites
and the actors to be considered in their use.
Properties o composites and their raw materials given in this document are typical
or average gures. It is important to use the actual product data rom the suppliers
when designing products with composites.
5.1 Design
Composites are less successul when they are used to replace another material
without considering its specic design. For example, composite pipes are less sti
than metallic pipes, and thereore the supports need to the placed more closely
together when installing composite pipes. Such actors have been considered in
the various design standards or composites.
It is important to engage composite designers and also have 3rd party verication
where appropriate. Specialist designers can be contacted directly or through the
composite manuacturer. Consideration o the various loads must be perormed
diligently and by those who have the background and knowledge o the materials
and structures.
Section 10 o this guide contains details or a number o Australian composites
design and engineering service providers.
5.2 Standards
Standards can be accessed at www.sai-global.com and other online stores.
AS 3571 Plastics piping systemsglass-reinorced thermoplastics (GRP) systems based on unsaturated
polyester (UP) resinpressure and non-pressure drainage and sewerage; and pressure and
non-pressure water supply
AS 2634 (obsolescent) Chemical plant equipment made rom glass-bre reinorced plastic (GRP), based on thermosetting
resins
AS/NZS 2566 Buried fexible pipelines
AS 2376.2 (superseded) Plastics building sheetsglass bre reinorced polyester (GRP)
AS 2424 (superseded) Plastics building sheetsgeneral installation requirements and design o roong systems
AS/NZS 4256.3 Plastic roo and wall cladding materialsglass bre reinorced polyester (GRP)
AS/NZ 2924 High-pressure decorative laminatessheets made rom thermoset ting resinsclassication and
specications
AS/NZS 3572 Plasticsglass lament reinorced plastics (GRP)Methods o Test
BS 4994 (superseded) Specication or design and construction o vessels and tanks in reinorced plastics
BS 6464 Specication or reinorced plastic pipes, ttings and joints or process plants
BS 6374-4 Lining o equipment with polymeric materials or the process industries, Part 4: specication or
lining with cold curing thermosetting resins
BS EN 13121 GRP tanks and vessels or use above ground. Design and workmanship
BS EN ISO 14692 Petroleum and natural gas industriesglass-reinorced plastics (GRP) piping.
Finite element buckling analysis o a large
breglass nozzle under external pressure
Image courtesy of Teakle Composites
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5.3 Guides
5.4 Relativeperformanceofmaterials
Table 6 Composite properties* compared to other materials
* The properties in this table are indicative only
ACI 440.1R-01 Guide or the design and construction o concrete reinorced with FRP bars, Committee 440,
American Concrete Institute, Farmington Hills, MI. (May 2001), www.aci-int.org
ACI 515.1R A guide to the use o waterproong, damp-proong, protection and decorative barrier systems
or concrete.
A guide or Flowtite GRP pressure and non-pressure pipe, engineering design guidelines, Iplex
Pipelines Australia, www.iplex.com.au
Material
Randomglass
composite
Bi-
directionalglass
composite
Uni-
directionalglass
compositeAramid
compositeCarbon
composite Aluminium MildsteelStainless
steel
Fibre content by
weight (%)
2550 4570 5090 4055 4059 0 0 0
Density (g/cm3) 1.41.9 1.51.9 1.62.2 1.4 1.5 2.62.8 7.8 7.92
Tensile strength
(MPa )
48170 190440 4101730 3452067 4102700 80480 200800 190552
Tensile modulus
(GPa )
618 1225 2162 1980 30180 70 190210 193200
Compressive
strength (MPa)
115170 98280 210480 102172 360 84338 410480 220552
Compressive
modulus (GPa)
69 817 - 1619 - - - -
Flexural
strength (MPa)
90340 200450 6901860 301 378 310 413 551
Flexural
modulus (GPa)
517 923 2748 15 28 69 207 193
In-plane shear
strength (MPa)
6296 5583 110140 - - 276 - -
In-plane shear
modulus (GPa)
2.83.0 3.04.0 4.15.2 - - 2630 7580 -
Tensile
elongation (%)
1.62.1 34.5 2.4 22.6 11.5 2.523 2237 40
Thermal
conductivity
(W/mC)
0.150.52 0.190.35 0.3 (in bre
direction)
1.7 (in bre
direction)
1.4 (90 to
bres)
34 (in bre
direction)
0.8 (90 to
bres)
140200 4350 110
Coecient o
linear thermal
expansion
(106/mm/C)
1833 916 9 (in bre
direction)
14 (90 to
bres)
4 (in bre
direction)
57 (90 to
bres)
0.5 (in bre
direction)
25 (90 to
bres)
23 1114 1618
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Figure 3. Stress strain curves o various materials
5.5 Servicelife
It is typical to speciy a minimum design lie o 20 years o continuous operation or
composite process equipments in the mining industry. In other industries, such as
underground water pipelines, a design lie o 100 years is more typical.
5.6 Mechanicalproperties
5.6.1 General
The mechanical properties o composites depend on a number o actors:
resin-to-glass ratio
orientation o bres
method o abrication.
Composites are anisotropic, which means their properties vary with direction. For
the mechanical properties discussed below, it is important to remember the values
will be dierent in the direction o the bres to that normal to the bres. In terms
o strength, composites have the greatest strength in the direction o the bres. In
the direction normal to the bres, the resin and the bre-resin interace determine
the strength, which may be one or two orders o magnitude lower than in the
direction o the bres. Designers must thereore avoid stress systems that result
in signicant loads normal to the bres.
Detailed design literature and programs are available to estimate the eect
o combinations o bres in dierent directions on the overall capacity o the
composite. Calculations o the anisotropic properties o composites require the
application o the theory o anisotropic elasticity or use o simpler means to obtain
reasonable estimates. For this type o work, the reader is reerred to the various
standards, guides and sotware programs available.
5.6.2 StrengthThe rule o mixtures is used to calculate the strength o composites. This rule takes
into account the relative ractions o the strength o both the bres and resin.
Tensile strength
The bres in composites are the principal contributor to the tensile strength o the
component. The resin has signicantly lower strength and acts to bind the bres
together and transmit the loads between them.
Compressive strength
The strength o the resin has a much greater infuence on the compressive strength
o composites than it does on the tensile strength. This is because the resin must
have sucient compressive strength to prevent the bres rom undergoing local
buckling or kinking under compression. The resin also helps to prevent ailurethrough longitudinal splitting. The resistance to buckling under compression can
be improved at the design stage by incorporating edge fanges, double curvature
and troughs.
Anti-static cable tray supplied for the
Blacktip Offshore Gas Production PlatformImage courtesy of Exel Composites
Stress
Yeild and ultimate
strength can be
considered the
same. Design is
to ultimate using
saety actor.
Stress
Strain
A. Composites
Yeild strength
lower than
ultimate. Design
is to yeild using
saety actor.Strain
B. Common metals
Non-linear
curves
depending on
polymer.
Stress
Strain
C. Non-reinforced plastics
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Shear strength
When subject to shear stress, the load-bearing abilities o the bres and
matrix, and the extent to which stresses are transerred between them, aects
the stiness and strength o composites. Most composites contain planes o
weakness between the layers which can result in interlaminar ailure in shear.
The property o interlaminar shear strength describes this behaviour.
Composites made rom abrics which have some bres in the z direction
(through-wall thickness), such as stitched cloths or chopped strand mat, are
more resistant to interlaminar ailure than composites made rom abrics
without bres in the z direction.
Flexural strength
Flexure/bending involves a combination o tensile, compressive and shear orces.
At a simple level, the tensile, compressive and shear properties o the materials
can be used in the design or fexure. However, fexural strength is seldom the
limiting criterion in composites, as stiness more oten dominates the design.
Stiffness
The stiness o composites is low compared to steel, although carbon bre-
reinorced composites are an exception. Since the tensile strength-to-weight ratio
o composites is high and stiness low compared to steel, stiness tends to be the
key determinant in structural design with composites.
The stiness o composite parts can be increased by:
selecting bres with a higher elastic modulus (e.g. carbon bres)
sandwich construction. Since stiness is a unction o thickness, cores can be
incorporated into a composite to provide rigidity, while keeping the weight low
localised increase in thickness, or example, progressive thickening along a
local edge or fanging along the edge o a panel
ribs can be incorporated into the reverse side o the part
compound curves or local corrugations. A olded plate construction can be used
to achieve the required stiness rom the overall geometry o the structure.
For most composites with more than about 50 per cent volume o bres, the
stiness in tension is dominated by the bres, and the resin contribution is
insignicant.
5.6.3 Fatigue
Fatigue is the progressive damage that occurs when a material is subject to cyclic
loading and when the stress values o each cycle are less than the ultimate stress
limit. For example, in the mining and chemical industries, tanks and process
vessels with internal agitators can be subject to constantly imposed stress cycles
and are thereore susceptible to atigue.
The atigue behavior o steel tends to involve intermittent propagation o a single
crack, while the material close to the crack is virtually unchanged. In contrast to
this, cyclic loading o composites results in the ormation o many micro-sized
cracks. Since the small cracks in composites are spread uniormly in the material
rather than concentrated in a single area, a greater area o material is involved in
resisting atigue ailure. Furthermore, as the ormation o each small crack absorbs
energy, composites tend to have good atigue resistance compared to most metals.
However, as damage accumulates, a critical point is eventually reached at which
the material can no longer sustain the applied load and ailure occurs.
To improve the atigue resistance o composites, resins which are tougher and have
greater resistance to micro-cracking should be used, and the amount o voids and
other deects in the laminate should be minimised. It is also important to ensure
the load normal to the direction o the bres is minimised.
Flowtite GRP Pipe (Continuous
Filament Wound) installed in South-East
Queenslands western corridor recycled
water pipeline
Image courtesy of Iplex Pipelines Pty Ltd
and Fibrelogic Pipe Systems