JOURNAL OF MATERIALS SCIENCE 10 (1975) 9 LETT ERS ~ 0 7O 6 O 50 ~40 2O 0 lO 0 30 40 50 ~ 7 TI ME (minutes) Figure 2 Wetting of borosilicate glass on evapora ted thin film of chromium in wet and dry N2 at 900~ in dry and we t N~ indicate that introducing a wet atmosphere is an effective way of lowering and maintaining the wetting angle. Dry nitrogen- containi ng atmospheres, on the other hand, seem to raise the wetting angle with prolonged time. The mechanism contributing to this increase in wetting angle is not known for certain, but it coincides with the deveiopment of mostly nitrides and a small amount of oxides in the surface of the film [5]. Whereas a continuous layer of Cr~O3 is always present in the surface of having been formed from 3 to 5 ppm O3 impurity in N2) and nitrides are present in dry atmospheres. This impl ies th at chromium oxides contribute to better wetting than nitrides. Unfortunately, no da ta are available to prove or disprove the effect of chromi um nitrides. It appears that water vapour lowers the wetting angles in both glass-ceramic and glass- metal systems. The mechanism by which this occurs is not kno wn for certain, but it appears t o be largely due t o lowering surface energy of gla ss by water vapour. References 1. J . A . ]"A s K a nd R . M . F U L R A T H , J. A me r. Ce ra m. So c. 45 (1962) 592. 2. B. W. KING~ I-I. P. TRIPP and w. H. DUCKWORTH, ibid 42 (1959) 504. 3. M. L. VOLPE, R. M. FULRATH a n d J. A. PASK, ibid 42 (1959) 102. 4. N. M. PARIKH, ibid 41 (1958) 18. 5. v. BRO SlC and E. I. ALLESANDRINI, J. Vae. Sci. Tech. 9 (1972) 8 3. Received 5 August and accepted 20 November 1974 R. R. TUMMALA B. J. FOSTER Glass Development Department, IBM East Fishkill, New York, USA Fibre orientation distribution in short fibre reinforced plastics A knowledge of the fibre orientation distribution is an essent ial pre-requisite in seekin g to predict the deformation behaviour of a short-fibre reinforced plastic. For asbestos fibres, wide- angle X-ray diffraction techniques have been applied with some success to the determination of the variation of fibre orientation distribution with po sition in an injection moulding [ 1 ]. This powerful technique cannot be applied in the important area of short glass-fibre reinforced thermoplastics and alternative techniques must be sought. The texture that is often visible in mouldings when examined in transmitted light or by 90 6 (macro) radiog raphy is not nec ess ari ly related to the orientation of the well-dispersed fibres that are primarily res pon sib le for the enhancement of the mechanical properties. Such texture or flow markings have been foun d to be misleading when predicting mechanical response [2] . Examination of individual fibre orientation has been widely performed using microtomed sections or surfaces prepared by the metallo- graphic polishing technique. The latter tech- nique is far more widely used since it is not restricted to translucent mouldings and causes less damage to the fibres and less disruption of their orientation. It is, however, a time con- suming and laborious task with the results sometimes disappointing due to lack of contrast between the fibre and matrix. 9 1975 Chapman and Hall Ltd.
5
Embed
Fibre Orientation Distribution in Short Fibre Reinforced Plastics
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
8/3/2019 Fibre Orientation Distribution in Short Fibre Reinforced Plastics
J O U R N A L O F M A T E R I A L S S C I E N C E 1 0 ( 19 7 5) 9 L E T T E R S
~ 0
7O
6 O
50
~40
2 O
0 lO 0 30 40 50 ~ 7
T I M E ( m i n u t e s )
Figure 2 Wetting of borosilicate glass on evaporated thin
film of chromium in wet and dry N2 at 900~
in dry and wet N~ indicate that introducing a wetatmosphere is an effective way of lowering and
maintaining the wetting angle. Dry nitrogen-containing atmospheres, on the other hand, seemto raise the wetting angle with prolonged time.The mechanism contributing to this increase inwetting angle is not known for certain, but it
coincides with the deveiopment of mostlynitrides and a small amount of oxides in thesurface of the film [5]. Whereas a continuouslayer of Cr~O3 is always present in the surface ofthe film in wet atmospheres, both oxides (oxideshaving been formed from 3 to 5 ppm O3impurity in N2) and nitrides are present in dryatmospheres. This implies that chromium oxidescontribute to better wetting than nitrides.Unfortunately, no data are available to prove or
disprove the effect of chromium nitrides.It appears that water vapour lowers the
wetting angles in both glass-ceramic and glass-metal systems. The mechanism by which thisoccurs is not known for certain, but it appears to
be largely due to lowering surface energy of glassby water vapour.
R e f e r e n c e s
1. J . A . ]" A s K a nd R . M . F U L R A T H , J. A me r. Ce ra m. So c.
4 5 ( 1 9 6 2 ) 5 9 2 .
2. B. W. KIN G~ I-I . P. TRI PP and w . H . D U C K WO R T H ,
i b i d 4 2 ( 1 9 5 9 ) 5 0 4 .
3 . M . L . V O L P E , R . M . F U L R A T H a n d J . A . P A S K , i b i d
4 2 ( 1 9 5 9 ) 1 0 2 .
4 . N . M . P A R I K H , ib id 4 1 ( 1 9 5 8 ) 1 8 .
5. v. BROSlC and E. I. A L L E S A N D R I N I , J . Vae . Sc i .
Tech. 9 (1972) 83.
Rece ived 5 Augus t
and accep ted 20 Novemb er 1974R . R . T U M M A L A
B . J . F O S T E R
Glass Development Department ,
IB M E a s t F i sh k il l, N e w Y o rk , U S A
F i b re o r i e n t a ti o n d i s t r ib u t i o n i n s h o r t f i b r er e i n fo r c e d p l a s t i c s
A knowledge of the fibre orientation distribution
is an essential pre-requisite in seeking to predictthe deformation behaviour of a short-fibrereinforced plastic. For asbestos fibres, wide-angle X-ray diffraction techniques have beenapplied with some success to the determinationof the variation of fibre orientation distributionwith position in an injection moulding [1 ]. Thispowerful technique cannot be applied in theimportant area of short glass-fibre reinforcedthermoplastics and alternative techniques mustbe sought.
The texture that is often visible in mouldingswhen examined in transmitted light or by
906
(macro) radiography is not necessarily related tothe orientation of the well-dispersed fibres thatare primarily responsible for the enhancement of
the mechanical properties. Such texture or flow
markings have been found to be misleading whenpredicting mechanical response [2].
Examination of individual fibre orientationhas been widely performed using microtomedsections or surfaces prepared by the metallo-graphic polishing technique. The latter tech-nique is far more widely used since it is notrestricted to translucent mouldings and causesless damage to the fibres and less disruption oftheir orientation. It is, however, a time con-suming and laborious task with the resultssometimes disappointing due to lack of contrastbetween the fibre and matrix.
9 1 9 7 5 C h a p m a n a n d H a l l L t d .
8/3/2019 Fibre Orientation Distribution in Short Fibre Reinforced Plastics
J O U R N A L O F M A T E R I A L S S C I E N C E 1 0 ( 1 9 7 5 ) 9 LETTERS
These d i f f icu lt ies a re remo ved by the use of the
t echn i que o f con t ac t m i c ro - r ad i og raphy (C M R )
[3] which has been ex tens ive ly appl i ed to b io-
log ica l mater i a l s for 20 years . CM R i s a modi f i ed
rad iographic t echnique in which the spec imen
t h ickness i s r educed i n o rde r t ha t t he num ber o f
images cas t does not c onfuse the to t a l p i c ture . Af ine gra in f i lm and developer a re used to enable
enlarged images of the nomina l 10 gm diameter
f ibres to be ma de w i thout pro blems of gra in s i ze .
F i na ll y , t he geom e t ry o f t he sy s tem fo r C M R is
chos en so th at th e f ibre sha dow is sufficiently wel l
reso lved to be c l ear on the f inal en largement s .
The reso lu t ion obta inable i s cont ro l l ed by the
f i lm gra in s i ze and the wid th of the pe nu mb ra [3 ] .
T he K o dak H i gh R eso l u t i on P l at e em p l oyed has
a gra in s i ze of 0 .25 gm w hich i s near the reso lu-
t ion l imi t o f t he opt i ca l microscope , permi t t ing
magn i f i ca t ion of x 500 wi tho ut d i ff i cu l ty . In the
wors t case of a f ib re ly ing on the f ree surface of a
100 gm th ick spec imen in contac t wi th theem ul s ion , t he penu m bra w i d t h o f t he f i bre
image ma y be m ade l ess than the f i lm gra in s i ze
by se t ting the focus- to- f i lm d i s t ance a t 50 cm. I f ,
i ns t ead o f a norm al focus X-ray tube , a f ine
focus tube i s used , t h is ma y be reduc ed to 25 cm.
The cont ras t be tween the image of the f ib re
and t he backg round m a t r i x depends upon t he
( a )
fig 2
f ig 1
( c , e )
Figure 1 Fibre orientation distributionin an injection moulded ASTM tensilebar of glass fibre reinforced nylon 66.(a) Location of section cut from barand areas of section presented in ac-companying figures. (b) and (c) Photo-graphs of two parts of the surface asprepared by metallographic polishing.(d) and (e) Photograph produced fromthe micro-radiograph of the section,corresponding to the parts illustrated in(b) and (c).
907
8/3/2019 Fibre Orientation Distribution in Short Fibre Reinforced Plastics
J O U R N A L O F M A T E R I A L S S C I E N C E 1 0 ( 1 9 7 5 ) - L E T T E R S
Figure 2 Variation o f fibre orientation through the thickness direction for the moulding shown in F ig. 1, determinedusing the CM R technique. (a) View from top to bo ttom surface (the approximate site of th is photograph on themicro-radiograph of the section is shown in Fig. 1a). (b) Part of the central region of Fig. 2a at higher magnification.
th i ckness of the f ib re in the d i rec t ion of the X -ray
beam and t he d i f fe r ence be t w een t he X - ray
absorp t ion coeff i c i en t s of t he f ib re and mat r ix .
Since this di fference increases wi th X -ray
wavelength , t he sof t e r rad ia t ions a re more
des i rab le . In prac t i ce , however , unf i l te red copp er
rad ia t ion i s found to g ive sa t i s fac tory resu l t s
and the shor t es t exposure t imes .
T he op t i m um spec i m en t h i cknes s fo r C M R
var ies wi th f ib re conten t and the or i en ta t ion of
the f ibres in the sect ion. Usual ly i t l ies in the
range o f 50 to 150 gm . The surface condi t ion i s
re l a t ive ly unimpor tan t ; t he only requi rement s
are tha t t he f ibre or i en ta t ion i s no t d i s turbed by
the cu t t ing process and tha t t he cu t t ing debr i s is
removed. Such spec imens a re eas i ly prepared
us ing a low-speed d iamond cu t t ing saw.
A s a com par i son o f t he C M R t echn i que w i t h
the convent iona l sec t ion ing and pol i sh ing
m e t hod , an i n j ec ti on m ou l de d A S T M t ens il e ba r
of g l ass re inforced nylon 66 has been mounted
and pol i shed on the p l ane shown in F ig . l a . T wo
micrograp hs o f the surface a re shown in F ig . l b
908
and c. A 100 gm sl ice was then re mo ved
para l le l t o an d inc luding the pol i shed surface and
exam i ned by t he C M R t echn i que . F ig . l d and e
are th en the ide nt ical f ields of view to tho se o f
Fig. lb and c, excep t tha t the f ibres seen are
not on ly those tha t penet ra t e the pol i shed surface
but a l so a ll t hose under nea th the surface to a
depth of 100 gm. The c l earer representa t ion
of f ib re or i en ta t ion d i s t r ibu t ion by the CMR
technique i s apparent . An unexpected l ack of
symm et ry in the f low pa t t e rns in the two corners
o f t he m ou l d i s show n m uc h m ore c l ea rl y
by the C M R t echn i que .
T he C M R t echn i que i s ex t r em e l y u se fu l fo r
examining the through- th ickness f ib re or i en ta-
t ion d i s t r ibu t ion in mould ings , as i l l us t ra t ed in
Fig. 2. This represents a sect ion near the centre
of the sl ice ident i f ied in Fig. la . Th e relat ively
high degree of f ib re a l ignment a long the ax i s of
the bar , and the t ransverse or i en ta t ion in the
cent ra l zone are read i ly apparent .
A m icro-rad iograp h of a sl ice f rom a com-
merc ia l mou ld ing in p igmented shor t g l ass f ib re
8/3/2019 Fibre Orientation Distribution in Short Fibre Reinforced Plastics