SAMPE BRIDGE CONTEST · density, tow or bundle size, weave style, etc. a w may range 2from 50 g/m...
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Transcript of SAMPE BRIDGE CONTEST · density, tow or bundle size, weave style, etc. a w may range 2from 50 g/m...
2015
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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.
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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
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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
MAXIMUM FIBRE VOLUME FRACTION
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
MAXIMUM FIBRE VOLUME FRACTION
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
MAXIMUM FIBRE VOLUME FRACTION
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.
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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:
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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)
FIBRE VOLUME FRACTION
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
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'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
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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
FIBRE VOLUME FRACTION
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:
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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
)
FIBRE VOLUME FRACTION
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)
FIBRE VOLUME FRACTION
UD
BIAXIAL
QUASI-ISOTROPIC
2015
RULE OF MIXTURES TENSILE MODULUS (T300 CARBON FIBRE)