introduction to composite structures -2

7/28/2019 Introduction to composite structures -2

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26th November 2012All rights reserved by DUT racing team

INTRODUCTION TO COMPOSITE STRUCTURESLecture 2 - Manufacturing & Mould design

1

Pradeep PandurangiChassis Department, DUT13

email: [email protected]




Part 1 Overview of Composites Manufacturing

Part 2 Processes [ Wet lay-up] [Vacuum Infusion] [Prepregs]

Part 3 Mould design

ROADMAP

2




SAFETY & HEALTH

3

Part 1 - Overview Part 2 - Processes Part 3 - Mould Design

Avoid skin contact with liquid resin

Protect clothing by wearing a lab coat

In a clean room wear a head-cap

Wear a mask with drilling composites

Read MSDS (Material safety data sheet)




RECAP

4


Structuralconcept

Material Processing




RULE OF MIXTURES

5


E1 = V f *Ef + V m*Em

V f + V m =1




COMPOSITES MANUFACTURING

6


High fibre volume fractionHigher Stiffness

Uniform distribution of fibresNeither resin rich or resin starved

No voids or porosity Reduced mechanical properties and

source of stress concentration

No foreign objects in the

laminateHence cleanroom

Requirements


http://slidepdf.com/reader/full/introduction-to-composite-structures-2 7/3926th November 2012All rights reserved by DUT racing team


7


Thermosets - How to meet requirements

Mould preparation

Impregnate fibres with resin

Lay-up

Consolidation

Cure




8


Clean

Apply Release agentWax

ChemicalRelease film


Mould preparation


Lay-up

Consolidation

Cure




9


By hand before/after lay-up

Vacuum

Pressure

Pre - Impregnated


Mould preparation


Lay-up

Consolidation

Cure




10


Hand

Tape laying machine

Winding

Variety of ways...


Mould preparation


Lay-up

Consolidation

Cure




11


Vacuum

External pressure

Hand ?


Mould preparation


Lay-up

Consolidation

Cure




12


Room temperature

High temperatureEpoxy :120 - 180 deg C


Mould preparation


Lay-up

Consolidation

Cure




WET LAY-UP

13


About Simple & Cheap

Dry Fabrics + Resin (Application by hand before/after)

Room temperature curing

Post curingExothermic reaction




WET LAY-UP

14


Process




WET LAY-UP

15


Process




WET LAY-UP

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Limitations

Ready for the DUT13 negative mould ?

Little control over fibre volume fraction,thickness,void content

Difficult to maintain uniform quality of parts

Creates a mess - Protect your clothes

Bad for health (over a long period of time)




VACUUM INFUSION

18


Process




VACUUM INFUSION

19


Process




VACUUM INFUSION

20


Limitations

Difficult to keep dry fibres in place

Quality highly dependent on experience [location of resin inlet/

outlets; flow-mesh placement]

DUT11 monocoque infusion




PREPREGS

21


About Prepreg = Fibres Pre-impregnated with resin

Highest fibre volume fractions [>60%]

Aerospace quality = less than 1% void content

Least extra resin = Lowest weight parts

Complicated shapes possible

Vacuum bagging (All consumables to be suitable for curing temperature)Clean room for laminating

Thawing




PREPREGS

22


Process




PREPREGS

23


Process




PREPREGS

24


Limitations

Out of autoclave ?

Size of part limited by size of autoclave

Freezer for storage of raw material

Limited shelf life and room temperature life of raw

material




MOULD DESIGN

25


Design criteria

Shape & Size of part

Type of curing




MOULD DESIGN

26


Design criteria


Type of curing

Concept of mould

Draft

Corner radii

Handling




MOULD DESIGN

27


Design criteria


Type of curing

Positive (male) /

Negative (female) /Both

No. of parts

Concept of mould

Draft

Corner radii

Handling




MOULD DESIGN

28





MOULD DESIGN

29


Design criteria


Type of curing

Concept of mould

Draft

Corner radii

Handling




MOULD DESIGN

30


Design criteria


Type of curing

Concept of mould

Draft

Corner radii

Handling




MOULD DESIGN

31


Design criteria


Type of curing

Concept of mould

Draft

Corner radii

Handling




MOULD DESIGN

32


Design criteria


Type of curing

Shrinkage allowance

Thermal expansion

Thermal mass

Stiffness of mould

Porosity




MOULD DESIGN

33


Design criteria


Type of curing

Shrinkage allowance

Thermal expansion

Thermal mass

Stiffness of mould

Porosity




MOULD DESIGN

34


Design criteria


Type of curing

Shrinkage allowance

Thermal expansion

Thermal mass

Stiffness of mould

Porosity

CTE of component

CTE of mould material




MOULD DESIGN

35


Design criteria


Type of curing

Shrinkage allowance

Thermal expansion

Thermal mass

Stiffness of mould

Porosity

Time to reachtemperature




MOULD DESIGN

36


Design criteria


Type of curing

Shrinkage allowance

Thermal expansion

Thermal mass

Stiffness of mould

Porosity




MOULD DESIGN

37


Design criteria


Type of curing

Shrinkage allowance

Thermal expansion

Thermal mass

Stiffness of mould

Porosity




SUMMARY

38

Do’s & Don’t

Planning critical - things like thawing, booking oven/autoclave

Eye for detail needed - things that puncture bag

Handling of parts - inprocess and after

Read the datasheet

Learn from the experienced- Later this evening

Be ready for unexpected surprises



REFERENCES

Manufacturing Technology for Aerospace Structural Materials by F.C.Campbell

Composites Manufacturing by Sanjay Mazumdar

Fiber reinforced composites, materials manufacturing and designby Mallick

Composite Airframe Structures by Michael Niu

AE4653 - Composites Trinity Exercise

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introduction to composite structures -2

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