introduction to composites structures- 1
TRANSCRIPT
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INTRODUCTION TO COMPOSITE STRUCTURES
1
Pradeep Pandurangi
Chassis Department, DUT13email: [email protected]
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Introduction to composite materials - Why, What and How
Applications of composite structures
Design of composite structures
OBJECTIVES - LECTURE 1
2
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1. Design Methodology -
Systems Engineering
2. Knowing the loads acting on
the structure
3. Judicious use of compositematerials
3
The lightest FSAE Race car @120 kg
LIGHTWEIGHT STRUCTURES
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1. Design Methodology -
Systems Engineering
2. Knowing the loads acting on
the structure
3. Judicious use of compositematerials
4
The lightest FSAE Race car @120 kg
LIGHTWEIGHT STRUCTURES
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HIGH PERFORMANCE STRUCTURES
Weight Stiffness Strength
Race cars
•Tyre load sensitivity
•Longitudinalacceleration
•Lateral acceleration
•Yaw inertia
•Energy efficiency
•Cascading effect
Why ?•Safety of driver (Driving design criteriafor crash nose)
Aircraft
•Longer range
•Higher payloadcapacity
•Energy efficiency
•Runway length for
•Maintainaerodynamic shape
•Passenger comfort/peace of mind
5
Identify the driving design criteria
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HIGH PERFORMANCE STRUCTURES
6
Take into account
Operating environment
Life of structure
Lifecycle Cost (Remember F-22/F-35)
Aesthetics
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HIGH PERFORMANCE STRUCTURES
7
Choose the appropriate material
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WHAT ARE COMPOSITES ?
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Two or more constituent materials
Combined macroscopically
Retain individual properties, hence different from metallic alloys
Constituents can be distinguished by naked eye
Combination gives better properties than separate constituents
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COMPOSITES
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Particulate Random short fibres
Flakes Long fibres
Types of reinforcements
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COMPOSITES
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Types of matrix
Ceramics
Metals
Polymers
Carbon
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FIBRE REINFORCED PLASTIC - FRP
11
Fibre = Carry loads
Polymer Matrix = Transfer loads between the fibres & protect from environment
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THE FIBRES
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GLASS CARBON
ARAMID BORON
E glass S glass
5 - 24 um Radomes
HS or HM
5 - 7 um
Man-made
Organic
Ballistic
Applications
Lowcompressive
strength
Thicker than other
fibres
Mostwidely used
Most
expensive
Shortfibres
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THE FIBRE FORMS
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Braids Bi-directional fabric
Uni-directional tape Rovings
Stacking of unidirectionalfibre layers to form a
composite laminate
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BD FABRICS - TYPES OF WEAVE
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Rovings
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BD FABRICS - TYPES OF WEAVE
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Rovings
Asymmetrical
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THE POLYMER MATRIX
THERMOSET
3D cross-linking
Once cured, do not soften onheating
THERMOPLASTIC
Branching, very little cross-links
Softened after curing by heating
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THERMOSET - EPOXY
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Resin+Hardener (+Accelerator)
High mechanical strength relative to other thermosets
Low cure shrinkage
Corrosive handling
Exothermic reaction
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McLAREN
McLaren MP4/1 McLaren MP4-12C
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OTHER POSSIBILITIES
Metallic integrationTube bonding
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BOEING 787 - 2011
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But why so late ?
AIRBUS 350 XWB - 2014?
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COMPOSITE MATERIALS
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Concept of Tailor-ability Different properties is differentregions of the structure possible
Features - Positive
Integrating functions=Part reduction
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COMPOSITE MATERIALS
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Features - Negative
More variables in design - Increased complexity
Less forgiving - Higher safety factor
Sensitive to production
Expensive raw material
Expensive moulds
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MECHANICS
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BEFORE DESIGN
MOULD
Thermal expansionSurface finish
De-moulding
LAY-UPCURING
To cross-link molecules of the matrix
High temperature+Pressure
=Autoclave
High temperature=Oven
Room temperature
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DESIGN OF COMPOSITE STRUCTURES
Structuralconcept
Material Processing
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Structuralconcept
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LAY-UP SEQUENCE
Laminate lay-up is according to the in-plane loads
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LAY-UP SEQUENCE
Tension-Compression
Which lay-up to choose ?
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LAY-UP SEQUENCE
Tension-Compression
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LAY-UP SEQUENCE
Tension-Compression
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LAY-UP SEQUENCE
In-plane shear
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LAY-UP SEQUENCE
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Quasi-Isotropic & Balanced laminate
Quasi Isotropic = No bend-twist coupling
Mid plane symmetry = No curing stresses
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LAY-UP SEQUENCE
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Continuous fibres = higher strengthOverlap builds up thickness !
Ply drops = Stress concentrations
Top layer covering ply drops preventsde-lamination
Overlaps & Ply drops
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LAY-UP SEQUENCELocal lay-up near holes
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LAY-UP SEQUENCELocal lay-up near holes
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ADHESIVE BONDING
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SANDWICH STRUCTURES
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INSERTS
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LOAD INTRODUCTION
In-plane: 20320 N Out of plane: 14898 N
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LOAD INTRODUCTION
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How do I expect the structure to fail ?
Which failure mode can I predict accurately ?
Does the failure of structure affect safety of driver or spectators ?
FAILURE MODES
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TESTING
Validation of computer simulation (FEA)
Validate failure mode predictions
Specimen sample from product - to check production quality of each
batch of components
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SUMMARY
“Think Composites”
Validate by testing
Take into account production processes from the star t
Think about mould design when deciding shape
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Composite Materials - Design and Application, Daniel Gay
Mechanics of Composite Materials, Robert Jones
SP systems guide to composite materials
AE4684 course material
DUT SES 2012
Google Images
Wikipedia
REFERENCES