"

NASA-CR-17361619840017699

A Reproduced CopyOF

Reproduced for NASA

by the

NASA Scientific and Technical Information Facility

LIBRARY COpyUr. r .. ? fllu..~

, ' IJ jjut'

LANGLEY RESEARCH CENTERLIBRARy, NASA

HAMPTON, VlrtGlNIA

FFNo 672 Aug 65

https://ntrs.nasa.gov/search.jsp?R=19840017699 2018-06-14T14:53:30+00:00Z

CCMS-84-·0l\lPI-E-8J..9

VIRGINIA IECH

CE TER FORCOMPOSa«fE !ViATEREJ\lSAND STRlJCTl~F(ES

240S1

Vh'ginia ~)ol,·te(:I'mk:

hutituteand

Scott Mii~n Mi~kcwkh

Carl T. ~aera»u)'likh

Temperature D~penden(e of Elastic and SirengthProperdesof T300/5208 (jraphi~e-EpoJt},'

«NASA-CR-17J616) TE~prRATOBG DEPENDENCE OF UBU-25167Lt;"STIC A!-W ~T.~El!G'fi.i PhUPEIl'I1£S UP nOO/52GS,,~"fi!IT;'~-E.P()XY nr.l.ryir..ia Pol yto;;;chnic Int>'i:."<lull Stdte (lIlt .. ..) 4.J P he A03/f'lf 1'.01 tJnclds

CSCL Hn GJ/2 1+ 13/:>11

College of Engineering

V1rgfnfJ Polytechnfc Institute and State University

Blacksburg, VA 24061

VPI-E-!33-9 April t 1984

~,~ii

Temperature Dependence of Elastic and StrengthPropert ies of T300/520B Graphite-Epoxy

Scott ~ilan Hilkovich 1

Carl T. Herdkov1ch 4

Department of Engine~rlng Science &Mechanics

Interim Report 41The r~SA-Virginia Tech Composites Program

NASA Cooperative Agreement NAG-1-343

Prepared for: Applied Materials 3ranchNational Aeronautics &Space Administrationlangley Research CenterHampton, VA 23665

IGroduate Student

2Professor of En9inee~1ng Science &Mechanics

i<',

ABSTHACT

Experimental results are prE.'Sent(~ for the elastic and strength

properties of T300/520U graphite-epoxy at room temperature. 116K

(w2tiOOf). and 394K (-t250°F). Results C2re presentl>d for unidirectional

UO. 90°. and 45° laminates. and ±30o, ±45°, and t6U IJ angle-ply lami··

nates. It is shown th,it the stress-strain behavior of the 0° and 9Uo

laminates is essentially linear for all three temperatures and that the

stress-strain behavior of all other laminates is l1ne·ar at 116K. A

second-order curve provides the best fit for the t~nperature dependence

of thf! elastic modulus of an laminates "nd for the principal $hf~i.H'·

modulus. Poisson's ratio appears to vary linf)arly with tempefatUI'~.

1\11 IllOduli decrease with increasing temperature except for £1 I'/hiC'l

exhlbits a small increase. The strength temperature depende'K.e 15 al'!,t

temperJture dependence. In many cases the tt:111perattH'E' dellendence of

properth..s is nearly linear.

2

1.0 INTRODUCTION

The use of fiber-r9inforced composite materials in the .1erospace

industry has greatly ificrec1scd in recent years. The gr'eat advantage of

these materials being their superior strenvth to weight and stiffness tJ

weight ratios. This rnal:es composite Hiat~r'als ideal for use in space~' :

app 11 cat1ons. In order to efficiently design structures for use 1n

space. it is necessary to determine the effect of the space-envir'onment

on these materials. The cold of space coupled w1tb radiant solar heat-

10g effects cao lead to a wide range of operating temperatures. Because

of this. it is necessary to understand how temperJture affects th~ basic

material properties of composite materials.

Obviously. strength and stiffne'!>s are two basic ffillt.erial pr(\pf~rties

whiCh are of fundclmenta 1 importance. Many proposed app1i cat 1ens of

fiber-reinforced material~ fOf' use in spac(!-er:vir'on~nts 'Involve gr'aph~'

fte-epoxy compos Hes. Tt,.: s paper presents data on the strength dnd

st1ffness propert i es of nOO/S20B graph ite-epoxy compos He over the

temperature range of 116K to 394K (-25l)e'F to +2S0°f). ;;1l:! des i gnati on

f300/5208 indicates that the graphite fibers are Thornel (Union Carbide)

nOD fibers in a matrix consisting of Marmeo 5208 epoxy r-esin. Tl1e

tel?'perJture range of 116K to 394K represents the temper'atw'e extremes

that llldy be cncount.:red ina spaee··envi ronment [l]. Di:tta 9 generated

from this study. arc presented in graphical form. (stiffness, strength

versus temper-ature and stress-strain curvps) as \icl13s in tabular

form. Test procedu:-es are di c;c\Jssed and comments reg3 ,'di ng materi a1

behavior are injected as warranted.

,~

i~_"''''~'_''__''_:_''''''~_AA"_'' ".~'--~'"-";-'~";~.--;'7 ';'''':;;;:;:;;;:'.;:''n.':-''''''·''''='''''''';;,-", «"""'" ...,_ .. , .. ~-'-''''''

2.0 PROC£ljURE

Test specimens were c:ut from panels of T300/5208 graphite-epoxy

that had been ultrasonfc1y C-scanned to insure their integrity. The

test specimens measured 1.27 centimeters by 25.40 centimeters (0.5

inches by 10.0 inches) and were 1.02 millimeters thick (0.040 inches).

This thickness corresponds to 8 lamina layers. Six different lailJinate

lay-up configurations were tested: (O]ti. (45]8' and [90J8 (all of which

are unidirectional lI'!atf.:ria1) as well as (+3°21-3°2]5' [+452/-452]5' and

(+60 2/-60 2]s' Tabs were not used for load introduction. After allowing

fOl' the gripping region. the aspect ratio (lengthh~ir.lth) of the test

weeks.

Prior to testing. each composite specimen \'las fitted with a r\~;:·

specimens \'1as twelve. Once the specimens had been cut to SLH~. they

WK-OO-120WR-350 (Hicro-Measure-

ments, !nc.) strain-gages Here used. Tht se gages \~ere choos.en bec.ausE;

were placed in a drying oven set at 373K (212 Q F) for a pedod of hio

tangular (45°) strain-gage rosette.

they are designed to ~"thstafld large tempe,'ature ranges. The gages wen~

mounted using M-Bond 6UO adhesive (r~icro-t'1easurements). fonowing the

suggested mounting proc~dure. This procedure includes lightly sanding

the composite surface to produce a smooth area were the stra'in-gage .is

to be located. Finally wide-temperature range lead wires were attached

to the strain-gage rosette (326-GJF. Micro~1easurements).

All t.ests \4ere pel'funned 1n an ATS environmental (;hamber that uses

res)stance element:; f('r l1eating and liquid nitrogen fOI' <;oo11ng. The

heat from the resistance elements is circtdated by an internal fan. The

liquid nitrogen evaporates as it enter's the chamber and is circulated by

4

a slight overpressure from the nitrogen source. Temperature is moni­

tored throughout the chamber by thermocoupl cs pl aced at var10us loca­

tions within the chamber. including one thermocouple attached directly

to the test specimen. Tests were conducted at three different tempera­

tures: 116K. 301K (room temperature). and 394K. Soak times of foul" to

six hours were required to attain stable conditions at the low test

temperture. Two to four hours were requi red at the hi gil test tempera­

ture.

The envi ronmental chamber was mounted on an MTS hydralic tensile

testing machine. The tensile machine was fitted with special "moffil::n1;-

free" grips which fit entirely within the chamber [2J. This fixture was

designed to provide accurate axi ..!l alignment 3r:d rotational fl'eedol11.

Load was measured by a resistance load cell located outside or the

chamber. During a test. stress and strain data \'4ere automatica1!j' .:'nd

periodically sampled and recorded by a computerized data acquisitiOi'l

syste.ll that is tied directly into the testing equipment. After each

test hatI been performed. ail test data is graphed. tabulated. and ana­

lyzed by computel'.

3.0 RESULTS

Sample stress-strain curves produced for this work are shown in

Fig. 1 through 6. f(e~ults of the tests performed are presented in

Tables 1 to 4. Data is catagorized by stiffness (Table 1). strength

(Table 2). Poisson's :-atio (Table 3), and shear modulus (Tahle 4). Each

teble is then ~ub-divided according to laminate lay-up and test tempera-

ture. The data is plotted as a function of temperature in Figs. 7

'.~ ".... ~,-\

....-

5

through 21, and the coefficients of a least-squares fit of the data are

presented in Tables 5 and 6.

3.1 Stress-Strain Curves-. ..,~_.._...

The data presented 1n Figs. 1 and 2 shows that stress-strain behav-

ior is nearly linear for both the 0° and 90°-material at all test

temperatlll'es. The pri nr. i pa1 moduli increase at both 116K (-250") and

394K (+2S0°F), with the larger increase occurring at the lower test

temperature. In all cases, very little nonlinear behavior is noted

prior to failure. The DO-material does exhibit a stiffening behavior at

high strains for room and elevated temperature (3].

Significant nonlinear behavior is exhibited in the stress-strain

curves at room and elevated temperatures for the other laminates 't~!sted

(Figs. 3-6). All four sets of stress-stra"in behav"jor ([45]8' [+302/"

302]5' [+452/-452]5> and [+6021-602Js ) show similar trends. At 116K

(-250°F) the stress-strain curve is esseJ"jtially linear. As the test

temperature is increased, the elastic modulus decreases and the degree

of nonlinearity increases. In ail cases. the 1arges. degree ofooo11n-

earity is exhibited at the high test temperature. This behavior is as

expected in vi ew of the kno...m i nfluenc0 of temperature on the response

of the epoxy matrix flldterial. The nonlinearity is more pronounced in

the laminates ~/hose behavior is more dominated by matrix properties.

The nonlinearity is not evident in the [90]a laminate because of the low

fai lure strain.

6

ORIGIN.J\L PAC!! f9OF POOR QUP.Lrrf

240.00 r-----------'----------,

1500.00

1200.00

300.00T300/52OB )GrlEp j [OJ8

- ROOM TEMPERATURE_.-. t-250°F (394°K)---- -250°F (116°K) I

025 Q~50 OJg-----tOO 0.00

STRAIN) PERCEl\JT

Stre5s-Str~1n Curves as a Function of Temperature forthe (0]8 Ldmfnate.

160.00

200.00

40.00

§2.....~ 120.00W0.::

tn80.00

Fig. 1..

,:1~'.

.,#

7

Stress-Str~in Curves as a Function of Temperature forthe [90]a Laminate•

Fig. 2.

ORIGINAL PM~£ isOF POOR QUALlTV

6.00• -1

35.00

5.00

30.00

4.0025.00

d?~ ~

-- (f)~

~3.00 2QOO CJ)

LLlCL: O:'~.- I-if) .15.00 (f)

2.00

10.00

1.00 T300/5208) GrIEp) [90Ja5.00- ROOM TEMPERATURE

--- t250°F (394°10•. _-- -2t:,O of (116°K)

0.0°0.00I ! - I -_..- con

0.08 0.16 0.24 0.32 . w

STRAI~~) PEr-rCFNT

..

8

"

..I

ORIGINAL PAG\! t9OF POOR QUALITY

24.00 r----- ,__, --1

.;

'i,., " 150.00

20.00

30.00

cP90.00 ~.

ta0:::::

~6000

120.00

II

II

II

II

II

II

I /

,/ (II ,

/f4.00 T30015208)GrIEp) (45)8- RCA-1M TEMPERATURE_.- t250°F (384°K)---- -250°F (! I GOK )

o 00 ._-,-_._-'- i ~-_._- 0.00, 0.00 0.25 0.50 0.75 1.00

STr~AIN, PERCEr\JT

B.OO -

IG.OO

en~

'"~ 12.00w~I-en

Fig. 3.. Stres.s-Strain Curves as a Ftmc:t1on of Temperature for the[45]8 Laminate"

.-

9

50.00

10000

25O.CO cE~

-'"200.00 ~

LLl0:::l-

15000 (f)

Stress-St,,~l''in Curves as a Function of Temperature for the(+30z/··;~Q2)s lcil'ill nate.

350.00

ORIGINAL PtH:'E ;f,OF POOR QUALITY

/I

II

I .

" ~/ .'

/1'I '

//I"

I ~

I T300/520e, GriEp) (i-30d- 3O~)sI - ROOM TEM PEHATIJRE

I _._ .·250"F (394"'K)I. -2500F (116"'K)"

O.OOo.ol:...o---,·-.I.--'---.l----- I --- 0000.20 0.40 O.GO 0.80'STRAIN) PERCENT

10.00

50.00

GO.Oor,...._.-------'----'---,-----.

40.00

§2...(J) 3QOO(/)w0:::l-eI>

2000

Fig. 4..

10

80.00

n<:!~....(f)

GO.oo if)W0::'I­(j)

40.00

20.00

120.00

100.00

ORIGINJ\.L pr\,.~E F.lOF r00R Q! l,l',l.,rrf

T300/5208) Gr/Ep) (t45z/-45Js--ROOM TEMPERATURE--- +250°F (394 OK)---~ -2.50°F UI6°K)

I I I --___ 0000.20 0.40 0.60 0.80'STRAIN PE!~CENT. ,

I /

I

;' /'I ,

/ YI '

/fI I

/ /

/ f/ f

II

II

II

Ir

II

l

3.00

0.0°0.00

15.00

18.00 I--~----

12.00

(j)~

"(J) 9.00U)W0::1--<.f)

6.00 ~

Fign 5. Stress-Strain Cur'lr's as a function of Temperatlwe for the[+45~/··452]s Laminate.

·.11

.~

Fig. 6•./ Stress-Strain Cur'ves as a Function of T~erature for the[+6021-60Z]s Laminate.

40.00

80.00

d?~(I}

60.00tf)LLJQ.':j­if;

12QOO

iOOOO

20.00

1

1

OHlGINAL PAGE r9OF POOR QUALl TV

9.00

6.00

12.00

15.00

IIIIIIII

I3.00 - I

I

III

0.00 L. -l--------L:--.-.-- 0.000.00 0.20 0.40 0.60 0.80

/ STRA.lN. PEF<CENT'}

18.00

(/)~

(f)"(f)LL.l0::~(f)

.. , ".' \

The results for the transver'se I\lOdulus E2f

This indicates that the epoxy ma

Since fiber properties dre independent of temper'iltlJretooperaturc.

temperatLlI'e re~ults. iflr.rea:'ing the t~;f"perilture above room temperatur'z

test temperature act"; to r.:.~lieve r(?:;idu,ll stresses, I>le lila,}' conclude th,)t

temperature value.

the transverse !nodulus ,.it the low temperature compared to the f'O-':l)1

(Fig_ 8, Tables 1 and 5) indicate th'lt thel'E is a 30 p\~r'cel1t inc:re<l~e in

this type of behavior at low teo1lpt.'i'iltures.

residual stresses.

that its effect on the modulus of the composite overrides the effect of

lower temperature Is a result of an incr'}iiSe in thi'! stHfnes~ of tht:>:

12

fibers should result ~n a hi\jher modolus of tl1'i! cOflip.)slte due to t\1~

absence of nonlinl;>ar IMtiix behavior (S~9]. The higher ITIoduh:s ell: tht;~

in lower lllC:trix stl'esses. Lower strt'sses in the IMtrh Mel str"igl't.nr

believed to be due prfmorily to reduced i'esidual stresses which rt~5u1t

3.2 Elastic Pr~pe~ties

fit are given in Table 5. The modulus is 6 to 7 percent higher at both

(over this range), the temperdture dependence observ.:d here is a fvnc-

tion of the changing matrix propt:rties. fiber wavIness, and resit1\J-:.l

much stiffer ilt the lower tel:lperature. Epades are known to (~xhlblt

OO-lamf;j(lt~. Tht1 cxpel'fment,11 tesults for the ela!>tic moduhlS t

El' are plotted ,1S a function of temperatuc'e fn Fig_ 7. Moduli value..

are presented in TaDle 1 and the coefficients of a second-order curve

elevated aCId low temperatures, ~s c(lmp~l'ed to th~t measured at rool1l

has much less influence on the trdnSVerSf.' m0<lulus. Since incf'E:a$in~1 th,;:

stresses (4]. Th~ higher md!Jlus at the elevated tempel'attlre is------ -..

--

..

-_.

13

01?p:" ..n C', t r'" 'r~ '9UF P(l.M,;i~ f~,,)-"1_~TY

40.0 ---...--------240.0

35.0 .I

210.0

30.0180.0

Q~(n~ 25.0 l?U'J 15QO "',

-}- - (./)Cf) (f)llJ 20.0

i LdZ 1200 _Oil'

t:.c:..I..L LLl.L. 15.0 Ll-I-- 9QO 1-(f) Cl)

10.0 GO.OT300/5208, GrIEp, (O)a

5.0 30.0

I0.0 _L_..L _.L.- _J 0.0

100 150 200 250 300 350 400

TEMPER/..\TURE> K

L ' _.__..1 .1_._.1 .1.--.__.1

-280 -190 -100 -/0 +·80 . +17'0 +2GO

TEMIPE·· f::J /\ T!JOE CI I \;-\ I I \ ) I

•

,~.

v..

4.0

3.5

3.0

(f)

~ 2.5""(J)

tG 2.0

6:I..L 1.5l--(j)

1.0

0.5

0.0100

14

ORIGINAL PACE isOF pom~ QUALITY

24.0

21.0

18.0 a0...

15.0(.9(f).....

(f)

12DldZlLLLan '-........~.-(/)

1 6.0T300/5208; GrfEpI [SOJa J

. . 13.0--'.-_L._._-L-._ ,_----1... " Q.O

150 200 250 300 350 400

TEfV1PERl.\TURE) K

'\

L_l...__l ...l-._! J._"--l·2BO ~ 190 ~ I00 ~ '0 +80 "'/70 +260

TEI\1PER/~TURE) I-

Fig. 8. Modulus of Elasticity~ £2. V~rsu$ Temperature~

•

..,

15

residual stresses do not playas ldrge a role in affect log trMs,,~rse

modulus 3S compared to their influence in the fiber direction. This is

cons i stent with the r~ch lower ion uence of (i bel' wa'li ne'iS on the trans-

verse stiffness •

45°-1amlnate: qU. This laminate \'135 chosen as the b0St specimen

for determination of the shear modulus, G12 , based upon the findings in

I'efer~nce [2] •. AVerdje results for the shear modulus, G12 , are plotted

in Fig. 9 and values for modulus and a second-ordtr fit are given in

Tables I, 4. and 5. The resuits were obtdined using a 45-unidir'ectional

off-axis speclme l) and the following st.;1nclard relationship (10).

where Ex is the mt'!dsurE!d axial modulus of the 45'"'-speClrifln and the oth.;!'

quanti t t es cOf'respond to prapert 1cs oj n the materi d 1 pro; nc i pa1 c'.)ordi na te

.sy':>tem. The results 1ndi cate that d second-order curve fit prO'll des In

excellent correlation of the tEmperature dependence of GIZ " The higher

~lle at the low temperature is consistt~nt with the temperature depen­

dent response of w~trix dominated properties.

The variation of the axial modulus. Ex. of the 45°-laminate wfth

temperature is shown in Fig. 10 and -/alues are given 'in Tables 1 ar.d

6. Comparison betl'Jeen experimental and theoretical values (Table 1)

indicates excellent agreement at room and elevated temperatures. but.

less than stisfactory agreement at the low temperature.

Poi SSO" I S rat i2_:_ \112. ThE: temperature dependf~n(.e of \112' (Fi g.

11) h essentLil1y linear, Clecreilsing \iith increasing temperature. The

16

200 ,-_.- --------12!X)

1.75

10.001.50

SK'>O&; ? (f)

1.25~ <..9,7.50 u5'~. '"

-~en

(f)t3 1.00GPO

LtJZ ZlL. 11..l!... 0.75 LL..I-

14.50 1--tf) UJ

0.&.1 3.00T300I5208) Gr-/Epl [4% I

0.25 J 1.50. ,

J~ 00 0 L __..L.-_.__J._.~--l.__ t 0.00, . 100 150 200 250 300 350 400~.

TEMPERATUI~E) 1<

•

L, 1 -----L.__......1--..1. j _ .,,_J.-280 -190 -100 -10 +SO tllO +260

TEMPE!~TURE) F

i

jI

17

ORIGINAL rAG\! ;9OF POOR QUAUT'i

•

2(100

10.00

30.00

4Qoo

50.00

,_300

T300/5208)Gr/Ep, [45]8

--_._---,,-------------1

L-_. L_·, L -l-280 -100 teO +260

TE~~PEFi!~TURt") F

1.00 -

0.00 1 ' ~-100 200

aoo[

7.00

6.00

if)5.002: -

(f)"\(f)

4.00WZLLlJ... 3pOl-(/)

2000

E.xFi9. lC. AX131 Modulus of the [45]a lami~ate Versus TemperJture.

..

..

18

ORiGINAL PAGE tSrOF POOR QUALITY

L-__ l. -"_~.. l

-280 -100 +80 t260

TErvlPERA\TUr~S F

0.80

0.70...

';(

0.60 ...0~

0.50<r0::

0.40(f)...Z0

0.30 en({)-0

0.20 o.~

'0.10

4000.00

,.-.--------

: L=:8,Gr~~p,(O:e

100 200 300

TE~J1PERATURE>K

· .l>~

~

;<'~

0.80,

,~,....0.70

,, .... ;\," 0,60.~

...0I-

0.50" «/,/ :~y 0:::ll·,

i (/)~~: 0040

f -z

i 0'",I

J,';';'l if) 030t if).·,~I:-

~, ~~~. 020t.":'~~;{j~

19

h1 gher Poi sson I s ratlo at the low tempel'atll re is sorn(!what sur Ilr1 s i n9 in

view of the elastic symmetry condition:

The modulus I'atio, El/f2~ is smaller at the low temperature compared to

the room tempel'Citu re rat f o. Thus a hf gher' v12 at the low ternperatu re

should be accompanied by a significa~tly higher \121 at the low tempera­

ture. While this trend was evident from the experimf:t1tal results, thl:

values did not correspond to satIsfaction to the E·\I relationship. In

fact, the ~asured value of \1 21 was l'\Jch too high. Accurdte measurement

,of the small strains involved is very difficult due to errors intf'od~lced

by the trdnSlJerSe sensitivity of the strain gages. In the case Qf 90o~

material, transverse sensitivity became prohibitively large compat'ed tc

the small strains that were measured.

An91e-a!,f~minates. Results for the effect of temperat!Jre on tlw

modulus of the angle-ply laminates tested are shown in Figs. 12-14., and

Tables 1 and 6. As the temperatLlre increases. the modulus decrease:; for

all lamil'Jate~. The decrease in modulus with temperature increase is

epoxy matrix becomes stiffer resulting in increased lcrninilte stiff-

3 to 6). As discu5sed in previous sections. at low temperatul'es the

also 'il1ustrated in the stress-st."alr] curves for these laminates (F'igs.

The stteSs-5tf'dfn curves exhibit incre\~sed nonlinearity ''lithness.

incre:ising temperature. nl'is results in dt:cred$(~d ove:"all stiffness in

the laminate. It should be noted here that reduced 'esidual stresses

(at higher temperature) are not N:pected to influence the stiffness of

these laminates nearly as much as it influences the stiffness of unidi-

.'

.'

r:c:(9

iff'(j)LtJZIJ....Lt..

l­e/)l

J

75.00

45.00

30.00

t- 60.00

T

------'._---

20

L--.--__.l- L . .J

~280 - 100 t80 +260TE~J]PERATUF~E) F

4.00 .

6.00

8.00

2.00

aoo1o!.-o-·----"--'----..J-------- 0.00200 300400

TEMPERATURE, K

12.00 ------

10.00

(j)

~

(/)""(/)wZ1..1­lLI­(!)

21

c£<"9

~,

(J)(f)WZLLI..!-i-­(f)

35.00

. 25.00

ORIGINAL PAm·: ISOf POOR QUALilV

45,00

. 15.00

55.00

.A..--- L. -l

··100 1'80 t2GOTEMPERt\TURE) F

5.00

---,-'- I ._-- 0.00200 300 400

TEI\1PERATURE, K

L-280

8.00

7.00

6.00

(f)5.00~

(J)(f)

4.00WZLLLL 3.00I-(f)

2.00

1.00

0°°100

1_.__.L ..l ._,---'

-280 -100 t80 .;.260

TEMPEHATURE, .F

55.00

5000

4500

4O!X)r£

35CO l?(j)....

3000 U)wZ

2EiOO LLIJ..-2000 l-(/)

15.00

•. iODO

5400

40000

7.00

ORIGINAL PAGE mOF POOR QUALITY

8.00

22

6.00

2.00 l '-~t--

1.00 L-=OO/:208,GrlEp,[rSOJ -SOJa

0·°,00 200--'~------

TE1\.1PERt4TUI~E) f-(

-~ 5.00

(f)'"

tG 4.00ZLLl.L. 3.00J=(f)

'"

..,

23

rectional material in the fiber direction. As with the 45~laminate,

{ompariSOil between experimental and theoretical values (Table 1) indi-

cates exce11 ent agreement .J.t room and elevated temperatu res, but 1ess

than satisfactory agreement at the low tC'mperature •

3.3 .~trel!9th Proe~rties

OO-lamin~l~.L.-!.T' Results for the temperature dependence of (.I"' ••

laminate strength, including the type of failure mode noted~ are shown

in Figs. 15 and 16. It is observed that the strength increases rleariy

linearly with increasing temperature. These results are apparently due

to changing mati Ix properties and residual stresses. At the lOI'JEH'

temperatur'e, the matri~ is brittle and stiff, .resulting in higher' resfd~

ual stresses and less efficient load transfer in regions of stress

concentr&tion such ~s at fiber broaks. The reverse is true at elev~tcd

temperatures.

The type of failure mode observed after the tensil e tests of [oJ8

laminates is indicated in Fig. 12. Th·~ room temperature dnd high tem-

perature tests both exhibit a "shatter-type" failure mode. ~jhen the

to the fibers into many small p'ieces. Very little of the original

composite test specimen fails in this mode, the specimen splits parallel

specimen is left intact. This phenomenom appears to ne more severe with

On the other hand, lm'l tel1lpel'ature tests

at lo\;~ test temperatures. Jhese results may be an indication that the

fiber/mattix bond is stl'cnger at tJ1e low temperature. This could be the

exhibit a "transverse-break" failure mode. Instead of splitting, the

compos'lte specimen fails by a single jagged break across its I'/idth.

This 1s further evidence that the matrix material becomes more brittle

increasing temperature.

I

~\

\\i

'. \'\.

..-- J~\iI

!I

~ 1I­I:,

O~O - J I ._L 1 --" ! 00100 /50 200 250 ?:IJO 3:0 4O'J

TEMPERATURE) K

oQ..~......(/)(f)LLJ0::I­(f)

600.0

12000

2400.0

2100.0

1500.0

1800.0

T300/5208) GrIEp) [Ol a

24

, . L-.--L I --_-L__...l-280 -190 -/00 -10 ~80 t-170 .. 260

TEMPERATURE) F

ORIGINJ\L Pf.\G~ i~

OF. POOR QUALITY

350.0

300.0

400.0

500

100.0

(f)~ 250.0

.....(/)

~ 200.00:::I-(f) 150.0

Fi 9.. 15.. Ul tirnate Str~ngth_ XT• Versus Teflllleratul'e.

..

/

Fig. 16. Failure Modes of the [uJ8 Laminate as a Function ofTempera t.u re.

+250' F (394K)

ORIGINAL PAGE ~g

OF POOR QUA.LlTV25

Room Tempe ra tu re

26

result of Ii much tighter "shrink'·fit" due to the higher r~sidual

stresses in the brittle matrix· material.

gOo-laminate: Yr. The results in Fig. 17 tndlcote that the trans-."

verse strength is not influenced strongly hy temperature. As indicated

In the figure. there is conside-rable scatter in the data at all three

test temperatures. This is typical of tests Qn gOo-material.

45°-hminate. The temperature dependence of the strength of this

laminate is shovin in Fig. 18. Clearly. there is significant variation

in str'ength depending upon the temperature. This laminate fails 11'\ it

mixed mode of lnplane shear and tr'allsverse tension. Thus it Is not 3

good specimen for determinatioi1 of fundamental properties. btlt rather­

useful for correlation of theory and experiment for failure under bfi1)!("

ial loading. Such compzlrison wi.ll not be made here. The results ari;

chosen for measure;nent of sheaj' roodu·lus e not shear str'ength.

~ngle··ply .lnmi!,dt~. Temperature deptmdent strl:ngth results for

the angle~ply laminates are presented in Figs. 19-21 and Tables 2 and

6. The data shows that laminate strength does not follow a consistent

trend as it function of temperature. \lbvivusly. these 1i'lminati?S are

affected in different \/3,YS and to di fferent degl'ees by the changes in

th~ cO'"l1os'lte inducHl by temp\~ratur-e. A complex interact10n occur's

ture). the increase in fiber-direction strel1gth (with incr'ed5ing tf!lilper-

atur-e). "nd the eff(~ct of residual stresses that mayor .nay not be

relieved hy combinations of th{~ above properties. All these intf:,rac:~

ti~H1S m,J;~l~ precise stre1lyth p:'i:,dict.ions difficult for' larninate'i.

.. -

• 2.7

Fi 9- 17_ Ul timate Strength. ¥To Vet'sus len\lerature.

&:<..:>u'f(j)!.JJ0::~U)

45.00

ORIGINAL Pi~Gt: fSOf POOR \)UALIn

------.,--,,'--..,-,---,-'--l' 6000

L__ _.- , -,_..1.......-....,__,_.._--1.-200 -100 ·:-60 , ~2GO

TErvlPEI~ATUR[> F

6.00

aoo

10.00

, ~----- .L ---....

4DO r' -=::O~:::OJ8 ::::L --'-_. -1--_... ODO

100 200 300 400

TEr\~PERl1.TURE.K.'

..

28

T30Ql5208) GrIEp) [45le

:: I_L__.~,t_'----l.__--l. t __"

100 !50 200 2f~O 300 350 400

TEfv1PERATURE) K

0.0

30.0

240.0

/80.00

0.:

/500 ~'"(/)

(/)

120.0Ld0::l-t/)

9QO

000

2/0.0

ORIGINAL PAGE (9OF POOR QUALITY

----_._----_._--_.....,

/5.0

20.0

40.0

10.0 .

30.0

35.0

(f)~ 25.0

uf(f)WC1::r­(/)

\:

L--I.----L----I.-_---L--.L__J-280 -190 -100 - 10 t·OO ·/70 ~ 260

TEMPERAlURE, F"

Fig. 18. Ultill1ate Strength of the [45]8 la.",lnate 'ier.'sI.IS Tempe-rature.

?9

ORlGINJ\L PI"; r~E P1OF POOR Qu,:\~.n"{

80.00 ..---._----_._------.._-

70.00 500.00

60.00

0.00

400.00 d?2:

20000

.30000

100.00

400_._--.L--.-..__.....

300

---------+-­~

J

QOO,oo ----- 2~O

TEfV1PER/.\TURE} K

2000 .

~ 50.00

~r 40.00LLJ0.::f-- 30.00(f)

' .."

I --1 .. _ L ..-l

-280 -100 t80 +260

TE~~PEf~ATURE) F

Fig.. 19.. Ultimate StrCl'l£lth of the [d02/-302]s laminate VersusTet~eratIH'e..

30

ORIGINAL PAGE isOF POOR QUALITY

40.0 ---"J240.0

35.0210.0

30.0180.0

&(f)~ 25.0 2"

15UO '"'l~ (()(()

C.f) 20.0if)

W 120.0 I.JJ0::

---+-~0.::

J- I-.Cf> 15.0

9"~OU1

10.0 GODT300/5208) GI"/Ep ) [v-45tf-45z!s

5.0 30.0

00 L-L._.....4.--._...1___L.__--L.-_._ OD. iOa 150 200 250 300 350 400

TEiVlPERATURE) K

l.-.--.L .! • . .• L ..L-.._...,_J. J

- 280 -190 - 100 - 10 t80 ~ 170 <~ 260TF\/iOER ""'IUDe F_I u' _ '..A. i l\L)

Fig. 20.. U1t~mate Streo9th of the [{'4S2!-452Js lamina.te Vcr'susTemperature.

"

"

"

, ,i

, '

31

40.0

240.035.0

T300/5208, Gr/EpJt60....I·roJ~ 210.0

30.0180.0

(f)25.0 &-~

150.0 ~'" ....(f)

(f)f{j 20.0 (J)

/20.0 w0::: cr::.-,- 1-el) 15.0900

if)

--~IOJ) - 60.0

5.0

~30.0

0.0,00i L- 1 •• 1 0.0

150 200 250 300 350 400

TEMPERATURE K.>

L .L__ I -L__ I J I

-280 -12-0 -100 -10 I-so ~170 l-200TE~J1PEI~ATURE > F

fig .. 21.. Ultimate SJ:.rength of the [+60ZI-60Z]s laminate Ver~u5Telilperatur~.

32

TABLE 1

Stiffness (Ex) Versus Temperature Data

La1..:!!Q. 116K (-250°F), 301K (H. ~.J. 394K, (+250~E.L

[0]8: El 157.9GPa (22.90msi) 147.7 (21.42) 156.0 (22.62)

[45]8 28.2 (4.089) 16.9 (2.452) 15.2 (2.211 )

<THEORETICAL>* 20.3 (2.950) 16.9 (2.450) 15.2 (2.210)

[90]8 14.5 (2.100) 11.1 (1.61.4) 11.7 (1.695)

[+302/-302]s 70.4 (10.217) 52.2 (7.578) 50.3 (7.291)

<THEORETICAl>* 6:.2 (9.160) 10.9 (8.420) 55.8 (8.090)

[+452/-452]s 31.2 (4.523) 20.7 (2.997) 18.2 (2 r;'~8)\ .0 ...

<THEORETICAL>* 27.0 (3.910) 23.8 (3.450) 20.3 (2.9&O)

[+602/-(;02]5 27.6 (4-.000) 12.5 (1.814) 14.6 (2.11~)

<HIEOREl lCAl>'" 17 .0 (2.470) 14.1 (2.050) 12.8 (1.860)

*C1uss;·:ai liHoil1atiofl theory

'-

.... -

//,.

33

TABLE 2

Strength (oult) Versus Temperature Data

Lay-up 116K (-250°F) 301K (r~. 'LJ. ,394K (+2S0"F)---- -

[O]a:Xr l,210MPa (175.7 ksi) 1,450 (209.7) 1.570 (228.0)

[45]8 82.9 (12.02) 120.9 (17.54) 78.9 (11.45 )

[90]a: Yr 33.2 (4.815) 28.3 (4.107) 32.6 (4.729)

[+3°2/-3°2]5 294.1 (42.66) 276.5 (40.10) 227.9 (33.05)

[+452/-452]s 101.9 (14.78) 112.5 (15.32) 104.4 (15.14)

[+602/-602]s 45.2 (6.56) 74.3 (l0.77) !i9.0 (8.55)

,/ .,

/I ',I'

34

TABLE 3

Poisson's Ratio (v12 ) versus Temperature Data

,/'

:~,

116K (-250°F)- '

0.4922 0.2979

TABLE 4

0.2098

Shear Modulus (G12) Versus remperature Data

7.85GPa (1.138105i) 6.94(1.007) 5.78 (0.8379)

.1 .,.. .

35

TABLE 5

-0.2753 x 10-4

-0.3993 r. 10-5

0.8674 x 10 n4

0.1258 x 10-4

0.2608 x 10-3

0.3782 x 10-4

'0.5184 x 10-3

0.7519 x 1.0-4

Coet'f1cietlts for Elastic and St.rength Temperatur~ Dependence

2p .. Co + C1, T + Ct T

where P Is the property of interest and T is in kelvin ••

..

Pro.Q.£!1l. ~.D.. h

£1 (Gr>a) 0.18~4 x 103 -0.2713 x 100

E1 (msf) 0.2645 x 102 -0.3935 x lO-1

£2 (GPa) 0.1961 x 102 -0.5429 x 10-1

E2(msi) 0.2844 x 101 -0.7874 x 10-2

"12 0.6092 x 100 -0.1021 x 10-2

i -I

0.7495 x 101 0.6599 x 10-2I Gi2 (GPa)II

I,' GI2 (ms1) 0.1087 x 101 0.9571 x 10-3

,I

X (MPa) 0.1060 x 104 0.1293 x 101T

Xl ("::ii ) 0.1538 x 103 0.1875 x 10°

YT (MPa) 0.4537 x 102 -0.1.'351 x 100

YI (ksi) 0.6580 x 101 -0.1960 x 10-1

, I

36

TABLE 6

f.,ropertl. .£0. h £4'

• 0.4069 x 102 -0.1257 x 10° 10,·3Ext [45J8 (GPa) 0.1552 x

Ex. [45]8 (msi) 0.5901 x 101 -0.1823 x 10-1 0.2251 x 10-4

EXt [+302/-302Js (GPa) 0.9143 x 102 -0.2140 x 10° 0.2773 x 10-3

Ex. [+3°2/-3°2]5 (ms;) 0.1326 x 10~ -0.3103 x 10-1 0.4021 x 10-4

Ex. [+452/-452J5 (GPa) 0.4158 x 102 -0.1023 x 10° 0.1089 x 10-3

Ex, [+452/-452J5 (ms;) 0.6031 x 101 -0.1483 x 10-1 0.1579 x 10-4

.EX' [+6°2/-602]5 (GPa) 0.5008 x 102 -0.2373 x 100 0.3734 x 10-3

Ex. [+6°2/-6°2]5 (msi) 0.7263 y. 101 -e.344J )( 1O~1 0.5416 x 10-4

[45J8

_ (j'lPa)')

0.1191 }{ lOl -0.2364 x 10-2au1t ' -0.2353 x 10(.

llu1 t' [45]8' (ksi) -0.3413 x 101 0.1728 x 10° -0.3429 x 10,·3

<1u1t • [+302/-3°2]5 (~1Pa) 0.2320 x 103 0.5455 x 10° -0.1537 x 10-2

(1ult~r4-"O 1 "0 ] (ks i ) 0.3648 x 102 0.7912 x 0-1 -0.2229 x' in,·3L'" 2 -j 2 s

O'ult • [+45 2/- 452]5 (t1Pa) 0.7709 x 102 0.2747 x 100 -0.5211 x 10-3

Cult' [+452/-4S2Js (ksi) O.llIS x 102 0.3984 x 10-1 ··0.7558 x 10-4

O'ult' [+60 2/-6J2]s (MPa) -0.1335 x 102 0.6392 x 100 -O.l1b6 x 10-2

°Ult' [+602/-602J 5 (ksi ) -0.1936 x 101 0.9270 x 10-1 -0.1677 x 10-3

...

"

II! -,-'

-.:;," _.. :-':'"

concentration, such as at fiber breaks. leading to decreased strength in

This disagreement

Straighter fibers tend to

becomes \'iorse ~lith increasing fiber-·angle, Possibly~ the increase in

brittle. A stiffer' matrix gillE:S rise to increases in stiffness in all

Comparison between experiment,l and theoretical values for laminate

At 10\'/ temperatures, the epoxy matrix material becomes stiff and

residual stresses and less efficient load transfer in regions of stress

orientatiQnsof the ,-;omposite. Strengtl is also increased in all cases

except the 0°-material. A brittle and stiff matrix re:..u1ts in higher

37

The results presented show that the elastic and strength properties

of nOO/5208 graphite·'epoxy com;msite va 1')' either linearly or quadra··

tically with tem?erature. The important properties of longitudinal and

transverse modulus (E1 2lnd E2) show slight increases at both high and

low temperatures. The remaining elastic properties exhibit a decrease

At elevated temperatures, I'educed residual stresses result in lower

4.0 SUMMARY

matrix stresses and str'aignter' fibel"s •

modulus. for the 4')o-lam"inate and the angle-ply laminates. indicates

excellent agreement at room and elevated tei1lperatl!res~ but less than

sati5factory agreerr;.::1t at the 1ow temper.)ture.

fl. and longitudinal strength, XT' are increased wh'l1e all other propel'­

ties are affected very 'little.

the fiber direction.

improve the properties of the composite in the fiber direction, but have

little effect in othel' directions. Therefore. 'the lorig1tl1dinal modulus.

with increasing temperature. Strength in tbe fiber-direction is linear

with an increase in strength accompan"ied by an increase in tempera­

. ture. All other strength I~asurements exhibit a second-order curve fit.

..:., .

/

•

38

modulus and brittleness in the matrix rr.aterial at lower temperatui'es has

an affect on angle-ply laminates that is not taken into consideration

with the classical iamination theory. t1ol'e work will have to be done in

this area to resolve this question.

ACKNOWLEDGEMENT

This work was supported by the NASA~V'i rg"inia Tech Composites Pro­

gram under NASA grant CA-NCGl-15. The authoi"$ would also like to thank

Peter Stein and Doug Wesley for their many hour!: spent assisting in the

1aboratory.

.\

I. ...

t,',.

39

REFERENCES

1. Tenney, D. R•• Sykes, Go F•• and Bowles, O. £., "Space EnvironmentalEffects on Materials," AGARD Conference Proceedings No. 327,Environmental Effects on l-1aterials for Spac~ Applications, paperspresented at the 55th mef:ting of the AGMD Structures and NaterialsPanel in Toronto, Canada, on 19-24 September 1982.

2. Pindera, M. J. and Herakovich. C. T., "An Endochronic Theory forTransversely Isotropic Fiber'ou5 Composites," VPI-E-81-?7, Virginia

. Polytechnic Institute and State University. October 1981.

3. Pinder'a, M. J. and Ht~ral.:ovich, C. T., "An Elastic Potential for theNonlinear Response of Unidirectional Graphite Composites," Journal~elied Mechanic~ Vol. xx.

4. Hyer', H. W., Herakovich, C. T., Hilkovich, S. H., and Short, J. S.,"Temperature Dependence of Mechanical and lhe,'mal Expansion Proper­ties of 1300/5203 Graphitl:!-Epoxy,1I _Gom!?.2.~jtes. Volume 14. July 1983,pp. 276 ..280.

5. Curtis, G. J •• Milne, .1. M., and Reynolds. \4. N.. "Non-HookeanBehavior of Strong Carbon Fiber'.;," Natu~-, Volum~ 220. December1968, po 1024•

6. Beetz, C. P., Jr., "Stro.in-Induced Stiffenlng or Carbon Fibres,"llbre ';;,£ien£.u.nd TecnnolQ.9Y.;. Volume 16, 198~.

7. Mansfield, Eo H. and Purslow, D., "The Influence of Fiber Wav~ness

on the Moduli of Unidirection Fib(;~i" Reinforced Composites." CP No.1339, December 1974.

8. Bazant. Z. P•• "Effect of Curvature of the Reinforci~g Fibers on theHoduli of Elasticity and Strength of Composites," PO·f..Lr!Ier Mechi0..1.s.?.,Volume 4, Number 2, 1968. pp. 251-258.

9. VanDreumel. W. ~l. M•• and Kamp, J. l. r1., "Non-Hookean Behavior inthe Fibre Direction of Carbon-Fibre Composttes and :he Influence ofFibre ~Javiness on the Tensile Properties." ,J. Composite Materials,VOlume ll. October 1977. p. 461. . --------.

, .(1I111~~lm~~r~)~~~~1111 ·, 3 1176 01310 7785 'I_- ...............~_~._-..... -

IJ'

.'.'

iI