Composite materials: challenges for the future -...

transcript

Modernization of two cycles (MA, BA) of competence-based curricula in

Material Engineering according to the best experience of Bologna Process

Composite materials:

challenges for the future

Jan Ivens

Lecture at the Sami Shamoon College of Engineering

Content

• Introduction

• Example of a smart material: shape memory foam

• Composite Materials

• Challenges for composite materials

• Answers through composites manufacturing

New materials?

At the start of the construction of the

Sagrada Familia (1882):

a few hundred materials:

Virtually no plastics

Now > 45000

No light-weight metal alloys

Now a few thousand

No composites

Now a few hundreds

Today: more than 160.000 materials

Antoni Gaudi

Scientific American:

9 Materials That Will Change the

Future of Manufacturing

Anisotropic plastics

Ultrathin platinum

coatings

Cheaper carbon fibre

Mega-magnets

Nano-crystals

Hard coatings

Thermo-electrics

Electric ink Intelligent foam

Filling the gaps in the Ashby maps

HOLE E/ρ

Contours of

Vector for

material development

Anisotropic and hybrid materials

Smart materials

GOAL: Energy efficiency –

material efficiency

Shape memory alloys

Shape memory polymers

Source: http://www.ctd-materials.com/products/emc.htm

Characteristics of the materials

response

TMA resultspeak stress relaxation stress spring back recovery stress

MPa MPa % MPa10% 65° 3.65 ± 0.45 1.95 ± 0.15 0,45 ± 0,35 1.65 ± 0.3

75° 2.4 ± 0.2 1.75 ± 0.12 0,25 ± 0,10 1.60 ± 0.0685° 2.2 ± 0.2 1.75 ± 0.15 0,15 ± 0,05 1.65 ± 0.12

20% 75° 5.9 ± 1.3 3.9 ± 0.5 2 ± 1 3 ± 1

0 10 20 30 40 50 60

Time (min)

Recovery 65°C– – – – Deformation 65°C––––––– Recovery 75°C– – – – Deformation 75°C––––––– Recovery 85°C– – – – Deformation 85°C–––––––

Universal V4.5A TA Instruments

65°C 75°C 85°C

Deformation

Recovery

Shape memory foam

• Light-weight part

• stability by dimension

• Minimize transport volume

• Versatile shape

• Customizing

Minimal transport volume

Ultra compressible

Controlled compaction

Regaining shape

diatom structuresHighly patterned with a variety of patterns, ribs,minute spines, marginal ridges and elevations

Internal heating by radiation

Prototype mould concept

1st injection

(interior)

Placing of heating

bundle

2nd injection

(exterior)

shape(heating

bundle

embedded)

heat and

compress

Design challenges

1. Functional use: dimensional stability

o Optimisation of the geometry

2. Creating the temporary shape

o Analysis of the deformation of the foam

o Design of the compaction process

3. Returning to the permanent shape

o Stimulus requirement

o Completeness of recovery

o Repeatability

4. Triggering the transformation

o Selection of heating elements

o Optimisation of distribution and heating control

5. Surface finish

o Scratch and wear resistant

o “look”

Composite materials

What is a composite material?

An artificial attempt to mimick the complexity of nature

Ex. bamboo

Hemicellulose

Lignin

Hierarchy in composites

3 meter

0.05 mm

0.005 mm

The constituents

• Fibres!

o Are very thin (0.01mm) hence very flexible (even if the material is intrinsically stiff)

o Can be woven, braided, knitted... and remain flexible, easy to handle

• The polymer matrix

o Is light, colourful or transparent, easy to shape,

o Can be liquid like water and hence easy to impregnate the fibrousreinforcements

Elementary steps for the manufacturing of a composite part

Impregnation

Resin/matrix

COMPOSITE

Consolidation

Knitting

WeavingBraiding etc

Fibres

Thermosets (epoxy, polyester)

Fibers Force Composite

Curing time

matrix

Resin Hardener

Thermoset

Thermoplastics (polypropylene, nylon,

PVC, PC)Fibers Heat

Composite

Thermoplastic

matrix

Prime application field: moving

objects

Carbon laminate

Carbon sandwich

Fiberglass

Aluminum

Aluminum/steel/titanium pylons

Composites

Aluminum

Titanium

The first composites in furniture design

• Charles Eames (1907-1978) !• Engineer in a Steel Mill … architect … designer … artist…

• … living in Los Angeles in the late ’40s• centre of modern airplane industry• glass fibres and polyesters invented

mid-30’s• first used in (military) airplanes during

Charles Eames’ discovery of

materials - 2• “plastic” chairs offered the solution: glass fibre reinforced polyester (both

materials developed only 10 years earlier!!)

The 60’s: technical experiments...

Verner Panton

(glass fibre-polyester,

later glass fibre-polyurethane)Eero Arnio

(glass fibre-polyester)

The introduction of carbon fibres...

Pol Quadens

(carbon fibre-epoxy)

The lightest chair in the world!

(< 1 kg)Alberto Meda

(carbon fibre-epoxy)

Thermoplastic composites ...

• Glass fibre-polypropylene, a thermoplast!

• Production method: injection moulding of short-fibre reinforced PP!

Jasper Morrison, 1999

(glassfibre-polypropylene) Stefano Giovannoni, 1999

(glass fibre-polypropylene)

Composites inspire designers

• Freedomo to experiment in small series

o of shapes, colours, textures in the material

• It’s hi-techo light, stiff ànd strong!

o Beware of fibre orientation and volume fraction

• On the wave of sustainabilityo Lighter products less energy consumption

Freedom of design and shaping

“Floris”, 1967, Günther Beltzig

(Glass-polyester)“Jet Desk”, 2008, Brodie Neill

(carbon-epoxy)

Freedom of design and shaping

Zaha Hadid

Yacht Blohm & Voss

• It’s hi-techo a real need: light, stiff ànd strong!

Comparing strength su vs. stiffness E

glas-UD

CFRP-0/90

CFRP-UD

Cr-Mo-staal

C-staalAlPA-glas

glas-PEs-mat

0 50 100 150 200 250

STIJFHEID (GPa)

Carbon fibre

glass fibre

STIFFNESS

Criteria for minimising the mass of a

square rod / flat plate (thickness free)

Bending of a flat plate:

Bending of a square

tension/compression

of a rod or plate

strengthstiffnessM = mass

CFRP-UD

CFRP-0/90

glas-PEs-UD

Alglas-PEs-mat

TiPA-glasPA

Cr-Mo-staalC-staal

0 1 2 3 4 5 6 7 8

SPECIFIEKE STIJFHEID (buiging)

Specific bending strength (su)1/2/

and bending stiffness (E)1/2/

Unidirectional carbon fibre composites

Polyme

Carbon

fibre 100%

Polymer 0%

60%Ec,l = Vf*Ef + Vm*Em

Ec,t = (Vf/Ef + Vm/Em) -1

Carbon reinforced composite (50% fibres):

weaves, random mats, short fibre composites

Polymer

Carbon

fibre 100%

50%50%

Polyme

Carbon

fibre 100%

Each fibre architecture gives different composite properties…

randomly

oriented long

composites

unidirectional

composites

Woven or

cross-ply

composites

Injection molded short

fibre composites

• It’s hi-techo a real need: light, stiff ànd strong!

Lightness is important for transport ...

Lighter cars lower fuel

consumption !

Boeing 787 Dreamliner: 50%

composites

Then … why don’t we use

composites all over (yet)?Composites face some challenges

o Freedom in shape

• Yes, If you have

• Enough time to make the part

• Enough money to pay for it

o High performance

• Yes, but

• Not in all directions

• Not all properties are high

o Light and thus environment friendly

• Yes, but

• High energy needed to produce the part

• Low level of recycling

Properties drop tremendously due to

fibre misorientationo For carbon-epoxy

Properties of laminated structures 50

Fibre length has a significant effect on

composite performance

Source: Spörrer, Sandler, Altstädt, UniBayreuth

Autoclave curing

l Pressure limited to 15 bar

l Large pressure chamber (autoclave)

l Complete temperature cycle (up to 15 hours!)

l High performance composite parts

l Aerospace

l Sports

l Base material “prepreg”

53April 2007-ivj

Resin Transfer Molding

• Schematic process description

o Fibrous reinforcement (precut or preformed) is placed in an open mold

o The mold is closed, the reinforcement is compacted

o Resin is injected at low pressure in the closed mold

o After complete filling, the resin is allowed to cure

o After cure, the part is demolded

Injection molding

• Pellets with short fibres

o Length 0.1 to 3 mm

• Very high pressure

o Up to 4000 bar

o Constraints on part size

• Short cycle times

o < 1 minute

• Low production waste

• Limited finishing times

• Properties

o Improved strength – stiffness

• Limited due to fibre length

o Improved thermal stability

o Reduced toughness

Enough time to make a part?

Series size

autoclave

Filament

winding

pultrusion

Hand lay-up

Spray-up

RIMInjection molding

thermoforming

Compression

molding

The holy grail of

composites manufacturing

Discontinuous fibres

Continuous

fibres

New technologies

LFT injection molding

LFT compression molding

Thermoforming with continuous fibre

High Pressure RTM

Combined technologies

Longer fibers in IM

• Injection molding:

o Short fibers in pellets

o Severe fiber shortening in extruder

• solution: long fiber thermoplastic (LFT)

59march 2009 Composites production technology 59

Effect of fiber length

New technologies

High Pressure RTM

Thermoforming with continuous

fibers• Goal: increase in mechanical properties

• Problems:

o Preimpregnated plates

o Reduction of formability

o Complex deformation mechanisms

Continuous Production on a

Double band press

Unwinding Stations

for Fabric and Polymer

Press Corpus

pressure and

temperature is applied

Impregnation,

consolidation and

solidification of the

material

Cutting station Palletizing

Deformation mechanisms

Thermoforming

Separate heating and forming

Forming pressure from 5 bar, since laminates are already fully consolidated

Cycle times typically within a minute

Reproducible process

1. Heating 2. Position of the

heated sheet

3. Forming

and cooling

4. Ejecting

of the part

5. Post

processing

New technologies

High Pressure RTM

Resin Transfer Molding

High pressure RTM

High Pressure RTM on snap-cure PU

injection

central

pressure

sensor

pressure sensors

at the side

injection

increase press power

from 200 t to 300 t

Injection time: 46 s

Reducing cost: better performance in less

Formulation “C”Formulation “C”

Formulation “C”

eFormulation “C”

Tensile

DInitial !

Results from EU-project HIVOCOMP (material: Huntsman)

Automation for improved productivity costs

BMW i3

New technologies

High Pressure RTM

Hybrid processes

• Problem statement

produce high performance complex parts in short cycle

• solution: hybrid processes

o Thermoplastics: short cycle

o Continuous fibers for high performance: thermoforming

o Disadvantage thermoforming:

• Limited complexity

• No integration of inserts, ribs possible

o Complex shapes: injection molding or compression

molding

Continuous fiber: FRTP sheet

• Sheet thickness: 0,05 mm – 6,0 mm

• Sheet width: 620 mm or 860 mm

• Fibers: glass, carbon, aramid

• Matrix: PP, PA6, PA12, PA66, PPS, TPU

• Fiber volume content: 35% - 60%

• Structure: unidirectional and

balanced

Separate heating and forming

Forming pressure from 5 bar, since laminates are already fully consolidated

Cycle times typically within a minute

Reproducible process

1. Heating 2. Position of the

heated sheet

3. Forming

and cooling

4. Ejecting

of the part

5. Post

processing

Thermoforming

Injection moulding of hybrid

structuresLFT moulding of hybrid

structures

Hybrid processing methods

Outer shell with

TEPEX®

Injected, short or long fiber

polymers to strengthen the part

and for function integration

Hybrid Forming

Examples (Audi)

Hybride

technieken

Thermo-

vormen

conclusion

Seriegrootte

autoclaaf

wikkelen pultrusie

Handlamineren

Spray-up

RIMspuitgieten

thermovormen

warmpersenLFT-IM

LFT-persen

HP RTM

Extra slides

Then … why don’t we (yet)?

Composites face some challenges

o Freedom in shape

o High performance

• Yes, but

Different fibre architectures, different composite properties…

Polymer

Carbon

fibre 100%

unidirectional

composites

cross-ply

composites

randomly

oriented

composites

Consequence: damage

• Delaminations

• Matrix cracks

How to minimize damage?

How to predict the effect of

damage on composite

properties

Improving toughness by controlled damage

Goal: to improve composite strain to failure without sacrifice of the stiffness

Long term interest: impact resistance, damage tolerance

Novel hybrids (brittle fibers in combination with ductile fibers)

How to introduce ductility in

the brittle composite?

Through control of the process

of damage development

PseudoductileBrittle

(a) (b) (c) (d) (e)

Delamination#1

Delamination#2

Delamination#4

Nanoscale toughening

no CNTs Curved CNTs Aligned CNTs

Effective μ-scale stress suppression‼ CNT orientation and waviness!

CNT localization

μ-scale stress concentrations elimination NO stress rise in rest of matrix

Smart CNT-networks: “bridges”

Location: high stress zones

Intelligent composites

sensor

on-board

computer

super-

computer

structural

health analysis

decision on

maintenance

Self-reinforced composites

• Self-reinforced polypropylene

o Fibre = drawn PP

o Matrix = isotropic PP

• Hot compaction

Apply T Apply P

Apply T and P

Kmetty et al., Progress in Polymer Science (2010)

Tackling brittleness: SRPP

Ward et al, Polymer (2004)

Tackling brittleness: tough fibres

Silk composites

Excellent falling weight impact performance!

Patent: WO 2007-110758

Steel fibre composites

5 mm5 mm

Steel fibre

Then … why don’t we (yet)?

Composites face some challenges

o Freedom in shape

o High performance

• Yes, but

Recycling options

But it’s not just recycling!

0% 20% 40% 60% 80% 100%

Passenger car

2t truck

4t truck

10t truck

Material production Parts & vehicle productionUse MaintenanceWaste Transport

Source: prof. Jun Takahashi, University of Tokyo

Energy cost in manufacturing

Carbon fibre:

Natural Fibres and Bio-polymers: why?

• Cost: often (potentially) low cost

• Less abrasive

• Good specific mechanical properties (low density)

• Natural image, design aspects, renewable and environment-friendly

• good acoustic & vibration damping, radar transparency, low CTE, ...

Specific tensile modulus E/rho (MJ/kg) for various

fibres

Flax fibre Bamboo

Glass fibre Carbon fibre

Specific FLEXURAL modulus (E(1/3)/rho in

N(1/3)m(7/3)/kg) for various fibres

Flax fibre Bamboo

Glass fibre Carbon fibreSp

Flax composites compete with glass

for tension

for bending

Need to optimize fibre orientation!UD, no twist

Special preforms for composites

UD PREPREGS ROVINGNON-CRIMP FABRIC

Future developments

• Manufacturing time

o Robustness of manufacturing

o Cycle times < 5 minutes

o Hybrid processing

• Toughness: Hybridization by combining

o Tough fibres with stiff fibres

o Continuous fibres with oriented discontinuous fibres

• Environmental aspects

o Recovery of fibres from composite waste

• Minimizing recycling damage

• Maintaining fibre properties

o Biocomposites

• Performant biopolymers

• Improved environmental resistance (water, UV)

Composite materials: challenges for the future -...

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