sampe bridge contest · density, tow or bundle size, weave style, etc. a w may range 2from 50 g/m...

SAMPE BRIDGE CONTEST

2015

FIBRE VOLUME FRACTION AND LAMINATE THICKNESS

2015

2015

40%

60% 60% 65% 70%

60%

40% 40% 35% 30%

0%

20%

40%

60%

80%

100%

Hand Layup Vacuum Bag Infusão Pré Preg Autoclave

FIBRE CONTENT X MANUFACTURING PROCESS

Fibra Resina Resin Fibre

Infusion

HOW MUCH REINFORCEMENT?

WEIGHT FRACTION USED IN MANUFACTURE. MAY REFER TO FIBRE OR RESIN - 'GRP' MANUFACTURERS WILL SPECIFY A GLASS CONTENT OF (E.G.) 25 WT%; A PREPREG SUPPLIER MIGHT GIVE A RESIN CONTENT OF 34 WT%.

VOLUME FRACTION USED IN DESIGN TO CALCULATE COMPOSITE PROPERTIES. ALMOST ALWAYS REFERS TO FIBRE CONTENT.

2015

WEIGHT FRACTION

VOLUME FRACTION CONVERSION

VW

W Wf

f f

f f f m

/

/ ( ) /

1

FOR THE SPECIAL CASE OF A TWO-COMPONENT COMPOSITE (EG FIBRE AND MATRIX):

WV

V Vf

f f

f f m f

( )1

2015

00,10,20,30,40,50,60,70,80,9

1

0 0,2 0,4 0,6 0,8 1

FIB

RE

VO

LUM

E FR

AC

TIO

N

FIBRE WEIGHT FRACTION

VOLUME FRACTION - WEIGHT FRACTION CONVERSION(EPOXY RESIN MATRIX)

GLASS

HS CARBON

ARAMID

2015

A COMPOSITE CANNOT CONTAIN 100% FIBRE. MAXIMUM VOLUME FRACTION COULD BE ACHIEVED ONLY IF UNIDIRECTIONAL FIBRES ARE HEXAGONALLY ‘CLOSE PACKED’ - IE ALL FIBRES ARE TOUCHING.

2015

MAXIMUM FIBRE VOLUME FRACTION

THE TRIANGULAR UNIT CELL HAS AREA 3 R2. THE UNIT CELL CONTAINS AN AREA OF FIBRE (THREE 60O SEGMENTS) EQUAL TO ΠR2 / 2

2R

3R

IN A UNIDIRECTIONAL FIBRE COMPOSITE, THE FIBRE AREA FRACTION IS THE SAME AS THE FIBRE VOLUME FRACTION, SO:

%91908.0323

22

2max

R

RV f

2015


THEORETICALLY, A UNIDIRECTIONAL FIBRE COMPOSITE COULD HAVE VF ≈ 91%. IN PRACTICE, FIBRES CANNOT BE PERFECTLY ALIGNED.

MAXIMUM VOLUME FRACTION DEPENDS BOTH ON THE FIBRE FORM AND METHOD OF MANUFACTURE - FOR A UNIDIRECTIONAL FIBRE COMPOSITE: VF ≈ 60-70%.

2015


FOR OTHER FORMS OF REINFORCEMENT, MAXIMUM VOLUME FRACTION ALSO DEPENDS ON THE DETAILED ARRANGEMENT OF THE FIBRES. THE FOLLOWING VALUES ARE TYPICAL: UNIDIRECTIONAL 0.70 – 0.72 STITCHED ‘NON-CRIMP’ 0.60 – 0.65 WOVEN FABRIC RANDOM 0.40 - 0.55 CHOPPED STRAND MAT 0.15 - 0.25

2015


HOW MUCH FIBRE?

COMMERCIAL REINFORCEMENTS ARE CHARACTERISED BY THEIR AREAL WEIGHT (AW). THIS IS SIMPLY THE WEIGHT (USUALLY GIVEN IN g) OF 1 M2 OF THE REINFORCEMENT. AW DEPENDS ON MANY FACTORS - FIBRE DENSITY, TOW OR BUNDLE SIZE, WEAVE STYLE, ETC.

AW MAY RANGE FROM 50 g/m2 OR LESS (FOR LIGHTWEIGHT SURFACING TISSUES), UP TO MORE THAN 2000 g/m2 FOR SOME HEAVYWEIGHT NON-CRIMP FABRICS.

2015

LAMINATE THICKNESS

THE THICKNESS OF A COMPOSITE LAMINATE DEPENDS ON THE AMOUNT OF REINFORCEMENT AND THE RELATIVE AMOUNT OF RESIN WHICH HAS BEEN INCLUDED. FOR A GIVEN QUANTITY OF REINFORCEMENT, A LAMINATE WITH A HIGH FIBRE VOLUME FRACTION WILL BE THINNER THAN ONE WITH A LOWER FIBRE VOLUME FRACTION, SINCE IT WILL CONTAIN LESS RESIN.

2015

LAMINATE THICKNESS

FIBRE

MATRIX

HIGH MATRIX CONTENT = LOW FIBRE CONTENT =THICK LAMINATE LOW MATRIX CONTENT = HIGH FIBRE CONTENT = THIN LAMINATE

TWO LAMINATES, BOTH CONTAINING 5 PLIES OF REINFORCEMENT:

2015

LAMINATE THICKNESS

FIBRE VOLUME FRACTION IS THUS INVERSELY PROPORTIONAL TO LAMINATE THICKNESS.

d

nAV

f

wf

IF THE FIBRE CONTENT AND LAMINATE THICKNESS ARE DEFINED, WE CAN CALCULATE THE FIBRE VOLUME FRACTION:

IF THE FIBRE CONTENT AND VOLUME FRACTION ARE DEFINED, WE CAN CALCULATE THE LAMINATE THICKNESS:

ff

w

V

nAd

2015

2015

0

0,5

1

1,5

2

2,5

3

0,1 0,2 0,3 0,4 0,5 0,6 0,7

PLY

TH

ICK

NES

S (M

M)

FIBRE VOLUME FRACTION

PLY THICKNESS VS FIBRE VOLUME FRACTION (GLASS)

200 g/m2

300 g/m2

450 g/m2

600 g/m2

AREA WEIGHT

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

0,2 0,3 0,4 0,5 0,6 0,7 0,8

PLY

TH

ICK

NES

S (M

M)


PLY THICKNESS VS FIBRE VOLUME FRACTION (HS CARBON)

100 g/m2

150 g/m2

200 g/m2

300 g/m2

500 g/m2

AREA WEIGHT

2015

RULES OF MIXTURE FOR

ELASTIC PROPERTIES

2015

'RULES OF MIXTURES' ARE MATHEMATICAL EXPRESSIONS WHICH GIVE SOME PROPERTY OF THE COMPOSITE IN TERMS OF THE PROPERTIES,

QUANTITY AND ARRANGEMENT OF ITS CONSTITUENTS.

THEY MAY BE BASED ON A NUMBER OF SIMPLIFYING ASSUMPTIONS, AND THEIR USE IN DESIGN SHOULD TEMPERED WITH EXTREME

CAUTION!

2015

RULES OF MIXTURE FOR ELASTIC PROPERTIES

DENSITY

FOR THE SPECIAL CASE OF A FIBRE-REINFORCED MATRIX:

mmff VV

SINCE VF + VM = 1

mfff )V1(V

mmff )(V

2015

RULE OF MIXTURES DENSITY FOR GLASS/EPOXY COMPOSITES

0

500

1000

1500

2000

2500

3000

0 0,2 0,4 0,6 0,8 1

KG

/M3


f

m

2015

GENERALISED RULE OF MIXTURES FOR TENSILE MODULUS

E = hL ho Ef Vf + Em (1-Vf )

hL IS A LENGTH CORRECTION FACTOR. TYPICALLY, hL 1 FOR FIBRES LONGER THAN ABOUT 10 mm.

hO CORRECTS FOR NON-UNIDIRECTIONAL REINFORCEMENT:

2015

0

10

20

30

40

50

60

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8

TE

NS

ILE

MO

DU

LUS

(G

PA

)


UD

BIAXIAL

CSM

2015

RULE OF MIXTURES TENSILE MODULUS (GLASS FIBRE/POLYESTER)

020406080

100120140160180200

0 0,2 0,4 0,6 0,8TEN

SILE

MO

DU

LUS

(GP

A)


UD

BIAXIAL

QUASI-ISOTROPIC

2015

RULE OF MIXTURES TENSILE MODULUS (T300 CARBON FIBRE)

sampe bridge contest · density, tow or bundle size, weave style, etc. a w may range 2from 50 g/m...

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