NASA Contractor Report 172164

FABRICATION OF SLENDER STRUTS

NASA-CR-172164 19830023462

FOR DEPLOYABLE ANTENNAS

R. MI. BLUCK AND R. R. JOHNSON

LOCKHEED MISSILES & SPACE COMPANY} INC. SUNNYVALE} CALIFORNIA 94086

TASK ASSIGNMENT NO. 24 CONTRACT NAS 1-14887

APRI L 1983

NI\S/\ National Aeronautics and Space Administration

langley Research Center Hampton, Virginia 23665

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https://ntrs.nasa.gov/search.jsp?R=19830023462 2018-07-10T21:09:13+00:00Z

NASA Contractor Report 172164

FABRICATION OF SLENDER STRUTS FOR DEPLOYABLE ANTENNAS

R. Nt BLUCK AND R. R. JOHNSON

, LOCKHEED MI SS I LES & SPACE COMPANY} I NC I

SUNNYVALE} CALIFORNIA 94086

TASK ASSIGNMENT NO. 24 CONTRACT NAS 1-14887

APRI L 1983

NI\5/\ National Aeronautics and Space Administration

Langley Research Center Hampton, Virginia 23665

NB3-3J73~

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CONTENTS

ILLUSTRATIONS v

TABLES vii

INTRODUCTION 1

DESCRIPTION OF STRUTS 1

PROCESS RATIONALE 2

MANUFACTURING PROCESS 8

VERIFICATION REQUIREMENTS 1.1

iii

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1

ILLUSTRATIONS

Graphite Epoxy Struts, Aluminum Foil Skin­

Gl'aphite Fiber: T-300

2 Graphite Epoxy Struts, Aluminum Foil Skin­

Graphite Fiber: 55 MSI Pitch

3 Graphite Epoxy Struts, Aluminum Foil Sldn­

Graphite Fiber: 75 MSI Pitch

4 Graphite Epoxy struts, Aluminum Foil Skin­

Graphite Fiber: 100 MSI Pj.tch

5 Overall Winding Setup

6 Closeup From Top

7 Looking Upward

8 Fabl'icated Tubes

v

4

5

6

7

10

10

10

10

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To Keep Document Continuity

TABLES

Ta.ble ---

1 Estimated Properties 3

vii

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To Keep Document Continuity

INTRODUCTION

Large diameter aperture antennas have been identified by government and

industry studies as a requirement for radiometer and communication missions for

the 1990 time frame.

The inherent stiffness associated with tetrahedral truss structures makes

them particularly well suited for this application. The work described in this

report deals with the manufacturing development of slender struts required for

the efficient stowage of such deployable trusses in the Orbiter cargo bay. A

number of features are included in both design and the manufacturing process.

The strut design includes an overwrap of aluminum foil which significantly

improves the thermal conductivity, and has the potential to act as a vapor bar­

rier if necessary, and provides a thermal control surface.

A number of elements have been introduced into the manufacturing process

which reduces the labor intensive aspects of fabricating these elements.

Included among these elements is the use of a vertical winding machine, teflon

mandrl31, dry fiber placement, aluminum foil winding off of canted spools, and a

pre-wound creeled fiber array.

DESCRIPTION OF STRUTS

Long slender tubular struts approximately 5-m long and 12.7-mm in diam have

been identified by the NASA Langley Research Center as the elements required

for efficient stowage and deployment of large truss supported antennas.

Although strut requirements have not been fully defined at this time, they must

be stiff and thermally stable. One concept for achieving these properties is

the us-e of high modulus graphite epoxy, oriented in the longitudinal direction,

overwrapped with thin aluminum foil. Use of the foil provides the potential

for significant improvements over conventional graphite epoxy struts. The more

important of these features are an improvement in thermal conductivity and the

incorporation of a vapor barrier. Thermal gradients, which are a result of

nonuniform heating will be reduced as the conductivity is increased. The use

of an aluminum surface has been shown to almost completely control the absorp­

tion (or desorption) of moisture, if it is a problem.

1

Estimated properties have been determined for four types of longitudinal

fiber/epoxy, overwrapped with aluminum foil. These properties are based on the

data shown in Table 1, for a 60-percent fiber volume, and are presented in

Figs. 1 through 4. The four types of graphite fiber are T-300, VSB-32(55

MSI), VSC-32(75 MSI), and VS-0054(lOO MSI). The effect of a thin aluminum

layer is readily evident. For example, the addition of a layer of 1 mil of

aluminum on the surface of an 0.020-in. wall of P-75 (Fig. 3) GR/E results in

a transverse thermal conductivity of approximately 3 Btu/hr-ft-OF, compared

with 0.1 for bare GR/E. This is accomplished with almost no reduction in

modulus of elasticity (43 versus 44 MSI). In this case, the coefficient of

thermal expansion (CTE) is negative (-0.5 /oF). A zero CTE can be obtained

using 100 MSI pitch fiber and 3.5 mils of aluminum, curve 3, Fig. 4. For this

example, E is 47 MSI and K = 32 Btu/hr-ft-oF. The density of such a structure

is 0.075 Ib/in. 3

For cases where a slightly negative CTE is desired to compensate for

positive CTE joints and fittings, it is possible to obtain higher values of E,

and lighter weight structures.

Point (A), Fig. 4 represents a modulus of elasticity to density (E/p) value

of approximately 109in • Although this point is for a bare (no aluminum)

graphite epoxy tube, it should be easy to achieve the 109 -in. value. A

65-percent fiber volume or a higher modulus fiber would make it possible to

obtain this value with the aluminum foil wrap.

PROCESS RATIONALE

The struts were wound on the LMSC vertical winding machine using dry

fiber. Two methods of introducing the resin were considered. One procedure

incorporated a doctor blade for spreading the resin during the winding

procedure as the carriage traverses from the bot tom of the machine to the

top. This procedure was used for manufacturing the parts which were wound

with aluminum foil. A second approach was to use resin injection for the

graphite

developed

parts without

during this

the aluminum foil wrap.

study. A brief discussion

This

of

procedure was

the rationale

not

for

selecting the mandrel, the vertical winding machine, and the fiber handling

system is presented below. 2

Table 1

ESTIMATED PROPERTIES

GR/E = 60-Pe.rcent Fiber Volume

T-300 P-55

EL - MSI 20 34

ET - MSI 1.5 0.9

0.29 0.3

GLT - MSI 0.66 0.6

CTEL ._ 10-6/ Cl F 0.05 -0.28

CTET ._ 10-6/ Cl F 16.5 19.0

- Ib/in. 3 0.057 0.58

kll - Btu/hr-·ft-OF 3.3 35

k22 - Btu/hr-·ft-oF 0.1 0.1

3

P-75 PI00 Al

44 60 10.5

0.9 0.9 10.5

0.3 0.3 0.33

0.60 0.6 3.97

-0.6 -0.79 13.0

19.0 19.0 13.0

0.063 0.067 0.10

58 137 76

0.1 0.1 76

LI.. 0

I I-LI.. 50 I a::: J: --:::> I-en

40 >-l-

> I-U 30 .t:: :::> 0 Z 0 U ...J 20 « :::2: a::: w J: l-a. 10 0 0 J:

>- 01 ~

LI.. 0 --\u

::t

Z 0 til Z « a. )( w ...J « :::2: a::: w J: I-u. 0 I-Z w -U LI.. LI.. W 0 U ...J « z -0 ::J I-(J Z 0 ...J

I x

II

GRAPHITE EPOXY STRUTS

ALUMINUM FOIL SKIN

GRAPHITE FIBER: T-300

LEGEND

Q) Qj

Q;

tGR/E(in.)

0.020

0.040

0.020

0.040

AL SURFACE ONE SIDE

X ----------

X

~ - - - --- ---- - ---

5.0

4.0

3.0

2.0

1.0

o

til .:2:

>­I-

U

li; 16 c:( ...J

w 14 LI.. o til 12 :J ...J :J o 10 o ~

...J c:( Z

o :J I-(J Z o ...J

x UJ

8

6

4

0 ...... o 2345678

tAL - ALUMINUM SURFACE FOIL THICKNESS (MILS)

9 10

-AL SURFACE BOTH SIDES

X

X -- -------

Fig. I Graphite Epoxy Struts, Aluminum Foil Skin-Graphite Fiber: T-300

\J1

60 ..... LL 0 I

l-LL I

a: 50 :I: -::J I-aJ

> 40 I-

> l-U ::J 30 0 Z 0 U ..J « 20 :E a: w :I: I-Il. 0 10 0 :I: I >-~

0

GRAPH ITE EPOXY STRUTS

ALUMINUM FOIL SKIN

LEGEND tGR/E (in.) AL SURFACE AL SURFACE

ONE SIDE 80TH SIDES

r1\ n n"')n v GRAPHiTE FiBER: 55 MSi PITCH I (jD I ~:~:~ X

--LL 0 -w 2.2 ::1. ..... z 2.0 0 I/)

z 1.8 « ll. X w 1.6 ..J « ~ 1.4 a: w :I: 1.2 l-LL 0 1.0 I-Z w 0.8 U LL LL w 0.6 0 U 0.4 ..J « z 0.2 0 ::J I- 0 (j Z o -0 2 ..J •

I x-O.4

lj

36

> 30 I-

U 27 l-I/)

« 211 ..J w LL 21 o I/)

::J 18 ..J ::J

g 15 :E

~ 12 z o 9 ::J I-

(j 6 z 9 I

® 0.020 X

I ® I 0.040 X

/ocx· ® /

/ /

/ /

/ K ® ) -- YR\ ~ - >Ex 0

... '/' <Xx CD , ® I

/ 1// / 1/ //-

Ex CD ' ® K CD, ®

Y

Ex®

// /;?/ 1/ //

/ //. !

/. I /.

I /~ ~ 'I /,y h ,::'l~ 1/7//:;.-"

,,/// v~ 'J~/ " I /,.,.;.4

..... <Xx ® /~K @

,~ Y

x w OL5 ________________________________ __

o 1 2 3 4 5 6 7 ,8 9 10 tAL - ALUMINUI\\ SURFACE FOIL THICKNESS (MILS)

Fig. 2 Graphite Epoxy Struts, Aluminum Foil Skin-Graphite Fiber: 55 MSI Pitch

0-

..... u. 0 I ...

U. I

0::: ::t: --::> f-CC

>-... > ... U ::> 0 z 0 U ..I <: :iE 0::: w ::t: ... w \I)

0::: LIJ > \I)

z <: 0::: ...

>­~

60

50

40

30

20

10

o

LEGEND tGR/E(in.) AL SURFACE ONE SIDE

GRAPHITE EPOXY STRUTS ALUMINUM FOIL SKIN

CD @

0.020 X

0.040 X

GRAPHITE FIBER: 75 MSI PITCH ® 0.020

2.0

1.8

1.6

... LL z 0 1.4 w --- '" U ::t

u. -1.2 u. z W 0 o - 1.0 U \I)

..I ~ <: a.. 0.8 Z x i5 W ::> ..I 0.6 ... <: l) :iE Z ffi 0.4 o ::t: ..J ... I u. 0.2 ijXO

o

-0.2

-0.4

-0.6

>- 40 ... U - 36 ... \I)

:5 32 w u. o 28 \I) ::> ..I 24 ::> o o 20 :iE ..I <: 16 z o ::> 12 ... l) z 8 o ..I I x

~--- 0.040 --- --- --_ .. _-------

,'" t3' / x \31

/ /

/ /

/ K Q) ( -=::::::::::=. y .' ,.,E

x @

//~/

I /

/ / / ./

E CD, ® x

Ky CD , ® '" CD, ® x E ® x

! // ./ ,<

/ / ", / /' ./ // ",'" ____ K

y@

/ / ",,-/ -----

I ",/ / ", / / /'" /' -_ ... ", @

/ Y/ -- X

", --0-

;,/ ----./ // ...... -I / ~ ,.,-

'I. ./ --w O~'r~1C __ ~~ ______ ~ ______ ~ __________ ___

o 1 2 3 4 5 6 7 8 9 10 tAL - ALUMINUM SURFACE FOIL THICKNESS (MILS)

AL SURFACE BOTH SIDES

X

X .- -------

Fig. 3 Graphite Epoxy Struts', Aluminum Foil Skin-Graphite Fiber :75 MSI Pitch

-.::J

...... u. o

I

t 60 I

a: ::I: -::> I-a; 50 I

>­I-

> 40 I-U ::> o z 8 30 ...J <C ~ a: w ::I: 20 I-w V)

a: w > V)

z <C a: I-

10

>- 0 ~

LEGEND I tG (in.) jAL SURFACEIAL SURFACE R IE ONE SIDE BOTH SIDES

GRAPHiTE EPOXY STRUTS

ALUMINUM FOIL SKIN

CD 2

0.020 x 0.040 X

GR,.t\PH!TE FIBER:

1.6

1.4 1- ...... Z u. 1 2 w 0 • -U w U. ::1. 1.0 u. w z o 0 U - 0.8

V) ...J Z « <C 6 z a. o. o ~ ~ ...J 0.4

<C a ~ Z a: 0.2 o w ...J ::I:

I I- 0 x U.

II 0

-0.2

-0.4

V)

~

>­I-

U l­V)

<C ...J W

U. o V)

::> ...J ::> o o ~ ...J « z o ::> I-

a z o ...J

I

55

50

45

40

35

30

25

20

15

10

® iOO MSi PITCH ®

0.020

0.040

Ex 0 ccx ® K y ®

Ex CD, ®

/

////~Ky~'@ / /~ --E (j\

;/

x \:V

/ // cc

I / '" x~' @

// ." / / /"''--- -K @

/.(/ ~ y

h/Y //? / // hh

• -" '" __ '" '2'

-0.61 w>- 5 V

/-r

__ x'-"

h . ---,h . ---~ -----

-0.8 o"'~ o 1 2 3 4 5 6 7 8 9 10

tAL - ALUMINUM SURFACE FOIL THICKNESS - MILS

X

X

Fig. 4 Graphite Epoxy Struts, Aluminum Foil Skin-Graphite Fiber: 100 MSI Pitch

A solid teflon rod was used for the mandrel to provide conlpaction, because

of its large coefficient of thermal expansion (CTE) during the cure process.

The teflon rod also provides an easy technique for the removal of the mandrel

from the finished part. The diameter of the teflon rod is reduced by applying

a tension load to the rod, and the part is easily removed.

The LMSC vertical winding machine was used because it provides the most

expeditious means to introduce longitudinal filament, and avoids mandrel sag

during winding. The use of a nonrotating mandrel precludes the potential of

mandrel whip.

A significant reduction in the labor intensive operation of loading the

fiber was achieved by using a Leesona winder to spool the fibers. The fibers

were then mounted on a creel. This procedure made it possible to wind a large

number of parts with only one loading of fiber.

MANUFACTURING PROCESS

The key elements of the manufacturing process include:

o Respool the fiber using the Leesona winder. Up to 1600 ft of single tow

can be wound on one spool.

o Install the 10-ft long 1/2-in diam teflon mandrel.

o Install the spooled fiber on the creel and thread the fiber through the

ceramic eyelets in the fiber alignment plate.

o Install O.OOl-in. thick aluminum foil on the canted stock spools. These

axes are canted to accommodate the aluminum foil overwind.

o Load resin into resin container (Fiber Resin (FR) 8701). During winding,

the resin is fed to a doctor blade for mandrel coating.

8

o The resin, longitudinal fiber, and aluminum foil overwrap are applied in

one pass to the mandrel as the carriage traverses upward.

The wound part is then inserted into a steam-heated, 3-in. diam tubular

oven for curing. After the part is cured, the tube is slipped off the mandrel

by applying mandrel tension, thus reducing the mandrel diameter. The tube is

cured on the mandrel at 250°F for 1 h and then at 335°F for 1 h.

A photograph of the overall setup of the winding operation is shown in

Fig. 5. A capriage is shown on which are mounted the creel of fiber spools, a

plate containing ceramic eyelets through which the fiber is fed, and a

gear-driven rj.ng to which the aluminum foil spools are attached. Also visible

in the picture is the vertically mounted l/2-in. diam mandrel. The length

below the aluminum spools has been wrapped with foil which captures the fiber

as it is wound on the mandrel. Figure 6 is a photograph showing in detail the

fiber being fed through the alignment plate. The spools of aluminum foil, and

the ring to which they are attached, are shown in Fig. 7. Completed tubes are

shown in Fig. 8.

Tubes with other fiber configurations were made using this procedure.

Specifically, a :tlO-deg graphite fiber tube with an aluminum overwrap was

manufactured. In this case, two passes were required. First, the +lO-deg

wrap was put on, and then the -IO-deg wrap and the aluminum foil. A simple

modification is required to the graphite fiber creel mounting. In laying down

unidireetional fiber with the aluminum overwrap, the spools of aluminum foil

are mounted on the rotating ring and the fiber creel is mounted on the

nonrotating frame. For the :tlO-deg configuration, the fiber creel is attached

to the rotating ring which makes it possible to wrap the fiber around the

mandrel"

The aluminum foil used is 1100 full hard (30 ksi UTS), 1/2-in. wide, and

was SelE!cted because it was readily available.

The amount of fiber in each part is precisely known, since a fixed number

of tows (spools) are fed through the ceramic eyelets.

9

L

Fig 6 Closeup From Top

Fig 5 Overall Winding Setup

Fig. 7 Looking Upward fig 8 Fabricated Tubes

10

VERIFICATION REQUIREMENTS

ThE~ objective of this task was to develop a manufacturing process and

demonstrate its feasibility. In this process of making the tubes, a number of

manufanturing elements has been demonstrated.

o AbHity to wind aluminum fiber with good adhesion

o USE! of creeled fiber in the winding process

o Development of a single-pass operation

o Ease of removing mandrel

o Ability to make slender straight tubing

Also, a tube was made with an aluminum foil inside and out by winding the

first foil wrap on the mandrel.

Although the manufacturing feasibility has been demonstrated, more

canplete control of the properties can be achieved by using hard tooling on

the outside, and injecting resin instead of the current technique of spreading

the resin by blade.

More impor'tant, however, is the need for verification of the physical

properties and manufacturing parameters.

In addition to a verification of the properties presented in Figs. I

through 4, a fiber volume and void evaluation are required. The performance

of the foil in the thermal cycling environment of space needs to be

evaluated. The efficiency of the foil as a vapor barrier could be of

considerable importance in some applications. Quantitative data are needed to

evaluate the validity of the manufacturing process.

11

1. Report No. 12. Government Accession No. 3. Recipient's Catalog No.

NASA CR-172164 4. Title and Subtitle 5. Report Date

April 1983 FABRICATION OF SLENDER STRUTS FOR 6. Performing Organization Code DEPLOYABLE ANTENNAS

7. Author(s) R. M. Bluck and R. R. Johnson

8. Performing Or:tnization Report No. LMSC- 889763

9. Performing Organization Name and Address 10. Work Unit No.

Lockheed Missiles & Space Company, Inc. 11. Contract or Grant No. 1111 Lockheed Way NAS 1-14887, Task 24 Sunnyvale, california 94086 13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address Contractor Report

National Aeronautics and Space. Administration Washington, D. C. 20546 14. Sponsoring Agency Code

15. Supplementary Notes

Langley Technical Monitor: Harold G. Bush Final Report

16. Abstract

A procedure for manufacturing long slender graphite tubing is desired. Such tubing has considerable application in truss supported spacecraft applications. The motivation for the selection of the tubing size developed in this program is for use as struts in a NASA, Langley Research Center truss supported antenna concept. The manufacturing procedure uses the LMSC vertical winding machine. A procedure for fabricating graphite epoxy tubing with an aluminum foil inner and outer wrap was also developed. The aluminum foil provides a vapor barrier, significantly improves the thermal conductivity, and provides an excellent thermal control surface.

17. Key Words (Selected by Author(s)) 18. Distribution Statement

Antenna Strut s -Graphite Epoxy Tubing Unclassified - Unlimited Aluminum Foil Surface Manufacturing Subject Category 24

-19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price *

Unclassified Un class ified 17 A02 . .

"For sale by the National Technical Information SerVice, Springfield, Virginia 22161 .

End of Document