acurex corporation/aerotherm. division aerotherm … · carbon phenolic (e.g., fiberite mx 4926)....

Acurex Corporation/Aerotherm. Division

March 1976

Aerotherm Project 7084

UNIFIED COMPUTER CODESPROPERTIES DATA FOR LOW COST

NOZZLE MATERIALSE. Chu

H. TongR. Bedard

AEROTHERM REPORT TR-76-9

Prepared for

National Aeronautics and Space AdministrationMarshall Space Flight CenterHuntsville, Alabama 35812

Contract NAS8-30264

'" ACUREX,~, Aerotherm

https://ntrs.nasa.gov/search.jsp?R=19760018254 2018-08-31T03:00:14+00:00Z

Section

2

3

4

5

6

TABLE OF CONTENTS

INTRODUCTION AND SUMMARY

MATERIAL SURVEY STUDY .

SUB-SCALE SCREENING TESTS

INTERMEDIATE TEST PROGRAM

MATERIALS FULL CHARACTERIZATION PROGRAM

5.1 Decomposition Kinetics5.2 Elemental Composition.5.3 Heat of Formation ..•5.4 Density .5.5 Specific Heat Capacity5.6 Thermal Conductivity .

5.6.1 Virgin Material Thermal Conductivity5.6.2 Dynamic Thermal Conductivity

5.7 Characterization Summary

CONCLUSIONS

REFERENCES .

APPENDIX A- RESIDUAL VOLATILE MEASUREMENTS

ii

Page

1-1

2-1

3-1

4-1

5-1

5-15-35-35-105-115-11

5-135-13

5-24

6-1

R-l

A-l

Figure

2-1

3-1

3-2

3-3

3-4

3-5

4-1

4-2

5-1

5-2

5-3

5-4

5-5

5-6

5-7

5-8

5-9

5-10

5-11

5-12

5-13

5-14

5-15

5-16

5-17

5-18

5-19

5-20

5-21

5-22

5-23

LIST OF ILLUSTRATIONS

Prepregged ablative material raw costs

Test configuration . • . . .

Screening test sample dimensions

Typical post-fired surface condition of hybrid carbon/phenolic materials

Typical post-fired surface condition of pitch mat/phenolic materials .•

Typical post-fired surface condition of carbon fabric/phenolic materials

Cured versus post-cured intermediate test results

Cured versus post-cured intermediate test results

Comparison of TGA data and CMA prediction





Measured virgin material thermal conductivity





Control volumes for in-depth energy and mass balances

Aerotherm constrictor are, rocket simulator configuration

Typical instrumented duct flow test section

0° char thermal conductivity .

90° char thermal conductivity

Comparison of in-depth thermocouple measurements and CMA prediction








; ; ;

Page

2-4

3-3

3-5

3-9

3-10

3-11

4-3

4-4

5-5

5-6

5-7

5-8

5-9

5-14

5-.15

5-16

5-17

5-18

5-19

5-22

5-23

5-25

5-26

5-27

5-28

5-29

5-30

5-31

5-32

5-33

5-34

Figure

5-24

5-25

5-26

LIST OF ILLUSTRATIONS (Concluded)



Char layer profiles for char conductivity test samples .

iv

Page

5-35

5-36

5-37

Table

2-1

2-2

3-1

3-2

3-3

3-4

3-5

3-6

3-7

3-8

4-1

4-2

5-1

5-2

5-3

5-4

5-5

5-6

5-7

5-8

5-9

5-10

5-11

A-l

LIST OF TABLES

Candidate Low Cost Materials for Shuttle SRM Throat Material Screening Test .

Candidate Low Cost Materials for Shuttle SRM Exit Cone Material Screening Test

Comparison of Rocket Motor and APG Environments

Comparison of APG Test Gas and Typical Nozzle Exhaust Gas EquilibriumComposition .....

Screening Test Matrix ..

Shuttle SRM Throat Material Screening Test Results

Shuttle SRM Exit Cone Materials Screening Test Results

Shuttle SRM Throat Materials Performance and Cost Comparisons

Shuttle SRM Exit Cone Materials Performance and Cost Comparisons

Selection of Shuttle SRM Low Cost Nozzle Evaluation Materials

Intermediate Test Matrix ....

Shuttle SRM Evaluation Materials Intermediate Test Results

Decomposition Kinetics of Low Cost Materials

Elemental Composition of Pyrolysis Gas •.

Nominal Values for Resin and Reinforcement Heats of Formation'

Heat of Formation of Virgin Low Cost Materials

Densities of Low Cost Carbon/Carbon Materials

Virgin Material Specific Heat Capacity ....

Thermal and Physical Properties of Pitch Mat Carbon Phemolic

Thermal and Physical Properties of Hybrid Pitch Mat/Rayon Fabric Phenolic

Thermal and Physical Properties of Pitch Mat Molding Compound

Thermal and Physical Properties of Pitch Fabric Phenolic

Thermal and Physical Properties of Canvas Phenolic

Screening Material Residual Volatile Measurements

v

Page

2-2

2-3

3-2

3-2

3-6

3-7

3-8

3-12

3-13

3-14

4-1

4-2

5-5

5-10

5-10

5-10

5-11

5-12

5-38

5-39

5-40

5-41

5-42

A-2

SECTION 1

INTRODUCTION AND SUMMARY

Rocket nozzles for the Space Shuttle SRM are being designed using materials which have been

. proven successful by many years of testing. However, the Shuttle philosophy of providing an econ

omical means of placing material and personnel into earth orbit requires a continued effort to reduce

mission costs. One area in which significant cost reductions can be realized is in the area of the

nozzle ablative liners. The primary high heat load material for current nozzles is a rayon precursor

carbon phenolic (e.g., Fiberite MX 4926). The material for lower heating conditions in the exit

cone and nozzle backside is a silica phenolic (e.g., Fiberite MX 2600). Over the past several years,

a number of low cost materials have been proposed as substitutes for the above materials; however,

the level to which these materials have been characterized was insufficient to allow a thermal anal

ysis of a full scale nozzle design. A need therefore existed to obtain the thermophysical and thermo

chemical properties of promising low cost materials.

low cost carbon phenolic materials development has centered on the replacement of rayon pre

cursor carbon with pitch precursor carbon. Using continuous filament pitch carbon fabrics, the pro

jected costs for carbon phenolic in the early 1980's may be about 23$/pound. Using pitch carbon mats,

the cost may decrease to as low as 12$/pound. Further reductions may be possible as pitch carbon makes

a deeper penetration into consumer goods. These projected costs may be compared to about 30$/pound for

current carbon phenolic prepreg.

Low cost materials development to replace current silica phenolics has centered on the use of

double thickness cloths and elastomeric resins to increase the component fabrication speed. Material

costs are not projected to be altered significantly in the next decade. Alternative reinforcements,

such as canvas, have also been considered.

The objective of this investigation was to develop the analytic capability to predict the thermal

ablation response of promising low cost materials. To achieve this objective, it was necessary to

1. Select potentially viable low cost materials. This was accomplished by a questionnaire and

telephone survey of material prepreggers and nozzle fabricators.

2. Experimentally determine the relative thermal performance of these materials. This was

accomplished by screening potential low cost materials in the Aerotherm arc plasma gener

ator.

3. Determine if materials of the same generic class but from different suppliers performed

differently. This was determined from the screening test data.

4. Select representative materials from each generic class and determine their thermophysical

and thermochemical properties. This was accomplished by appropriate characterization ex

periments.

5. Define these characteristics in a form which is compatible with current thermal performance

prediction techniques.

In the arc plasma generator ablation tests performed in Steps 2 and 4, Fiberite MX 4926 (carbon

phenolic) and MX 2600 (silica phenolic) were used as reference baseline materials. For the low cost

materials primary emphasis was on pitch carbon reinforced phenolics; however silica and canvas rein

forced phenolics were also tested.

The generic classes of materials selected for low cost evaluation were

1. Pitch carbon mat reinforced phenolic

2. Pitch carbon fabric reinforced phenolic

3. Pitch carbon molding compound

4. Hybrid pitch carbon mat/rayon carbon cloth reinforced phenolic

5. Silica reinforced phenolics

6. Canvas cloth reinforced phenolic.

Phenolic or elastomer modified phenolic was the resin for each generic class. Materials were

obtained from a number of prepreg suppliers. These materials were quantitatively compared in terms of

thermal performance by a simulation of propellant environments in an arc plasma generator. It was

found that material response was not very dependent upon the supplier of the material; however, a de

pendence on cure cycle was observed.

In order to provide data for analytic purposes, the thermophysical properties of these low cost

materials were evaluated. These data were assembled in a form which is compatible with current pre

diction procedures. As a result of this program an analytic capability has been established to pre

dict the thermal performance of new low cost rocket nozzle liner materials.

1-2

Aerotherm is pleased to acknowledge the cooperation and contributions of the Fiberite, Ferro,

Hexcel and U.S. Polymeric Corporations. These organizations responded to a lengthy questionnaire

and provided all of the required test materials.

1-3

SECTION 2

MATERIAL SURVEY STUDY

Since there is only limited knowledge of the performance of low cost materials in rocket

nozzles, a material survey study was necessary to capitalize on the background of material suppliers.

Such a survey study will not only enable one to have a better understanding of the thermal behavior

of low cost materials, it will also provide a better perspective in designing a test matrix for the

low cost materials performance study.

The survey study started with data collection. Material manufacturers and nozzle fabricators

were contacted to participate in this program and to propose promising low cost materials. The com

panies which responded were as follows:

• Fiberite Corporation

• Hexcel Corporation

• U. S. Polymeric Corporation

• Ferro Corporation

Questionnaires covering the areas such as material properties, fabrication techniques, cure procedure,

and material characteristics were sent to the above companies for their response. This information

was subsequently compiled and integrated qualitatively into a screening test matrix.

The second part of the survey study was to perform a qualitative analysis on the proposed low

cost materials based upon the information received. By utilizing mechanical and thermal properties

from qualified materials (MX 4926 - Shuttle SRM baseline throat material, MX 2600 - Shuttle SRM base

line exit cone material) as a guideline to analyze the proposed materials, less favorable materials

were eliminated before the screening test ..

The results of this study are shown in Tables 2-1 and 2-2. As can be seen, the properties of

the selected low cost materials are of the same order of magnitude as the qualified materials.

Information on the cost of some of the selected screening materials was also collected from

the above companies. An estimated trend of cost for each generic class of materials for calendar

years between 1975 to 1987 are presented in Figure 2-1.

2-1

N I N

TABL

E2-

1.CA

NDID

ATE

LOW

COST

MAT

ERIA

LSFO

RSH

UTTL

ESR

MTH

ROAT

MAT

ERIA

LSC

REEN

ING

TEST

Res

inT

ensi

leT

ensi

le/

With

Ply

Gen

eric

Tit1

eSo

urce

Mat

eria

lD

ensi

tyC

onte

ntS

tren

gth

F1ex

ure

Con

duct

ivit

yV

olat

ile!

Des

igna

tion

(GR/

CC)

Mod

ulus

Btu

-in

Con

tent

(%)

(KSI

)(M

SI)

Hr-

Ft-2

°F(%

)

Rayo

nCa

rbon

Fib

erit

eMX

4926

1.40

3418

.02.

73.

50.

56C

loth

Phen

olic

Pit

chM

atF

iber

ite

MX49

291.

4050

10.0

2.0

3.6

1.30

Car

bon

Phen

olic

USP

FM47

82BG

1.48

4512

.02.

44.

52.

05Fe

rro

ACX-

C86P

M1.

4043

5.0

1.38

Hyb

rid

Pit

chF

iber

ite

MX49

281.

4052

10.0

2.0

6.7

1.70

Mat

/Ray

onUS

PFM

5790

1.50

4413

.52.

52.

81C

loth

Phen

olic

Hex

cel

4CS

P08/

4C10

0845

1.47

Kyno

1C

arbo

nUS

PXF

M57

951.

4936

15.0

2.5

4.5

5.41

Clo

thPh

enol

icFe

rro

ACX-

CPH

411.

46

Kur

eha

Pit

ch4.

04C

arbo

nC

loth

Fer

roAC

X-C8

6i<42

Phen

olic

Pit

chM

atF

iber

ite

MXC

313P

1.50

377.

02.

02.

51.

08M

oldi

ngUS

PFM

5782

MC1.

6038

6.0

2.4

5.5

1.76

Com

poun

dH

exce

l4C

SPO

BMC

1.50

459.

52.

21.

69

Kur

eha

Pitc

hF

abri

cM

oldi

ngFe

rro

ACX-

C86K

MC

1.40

465.

82.

33Co

mpo

und

Pitc

hCa

rbon

Fib

erit

eMX

G10

33F

1.64

3223

.55.

02.

53.

80C

loth

Phen

olic

USP

FM57

955.

41H

exce

14C

1246

USP

itch

Fab

ric

Fib

erit

eMX

G10

33FM

CM

oldi

ngCo

mpo

und

ICur

edco

mpo

site

I,

N I W

TABL

E2-

2.CA

NDID

ATE

LOW

COST

MAT

ERIA

LSFO

RSH

UTTL

ESR

MEX

ITCO

NEM

ATER

IALS

SCRE

ENIN

GTE

ST

Aga

inst

Ply

Gen

eric

Tit

leSo

urce

Mat

eria

lD

ensi

tyR

esin

Con

duct

ivit

yD

esig

natio

n(G

R/C

C)

Con

tent

Btu

-in

Hr

-Ft

20F

Stan

dard

Sil

ica

Fib

erit

eMX

2600

1.74

334.

1C

loth

Phen

o1ic

Snap

wra

pSi

lic

aF

iber

ite

MXS

E-55

1.30

302.

2C

loth

Phen

olic

Dou

ble

Thi

ckS

ilic

aC

loth

Ferr

oC

A-2

221/

961.

7531

2.7

Phen

olic

Can

vas

Clo

thFi

beri

teM

XKF-

418

1.30

382.

2Ph

enol

icH

exce

l4K

9502

1.20

42-

..0 o ~ CANV

ASCL

OTH

PHEN

OLIC

STAN

DARD

AND

DOUB

LETH

ICK

SILI

CACL

OTH

PHEN

OLIC

RAYO

NFA

BRIC

!I

CARB

ONPHE~OLIC

30

±~W2jz

22

2t2

2<;/1

20~<

::7

P(,-C

H?F~R

IC?

/

10m}

$>$f}

$>S?f«

~

~ co ...J .....

. -~ ~ V'l

0 U W ;;- ..... ~ e:t:

N

...J

I

lXl

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e:t:

c w <.::l

<.::l w a: Q.

W a: Q.

7577

7981

CALE

NDAR

YEAR

8385

87

Figu

re2-

1.Pr

epre

gged

abla

tive

mat

eria

lra

wco

sts.

SECTION 3

SUB-SCALE SCREENING TESTS

The thermal performance of a number of low cost materials was evaluated by a screening test

program using an arc plasma generator (APG) as a convective heat source. The low cost materials in

this program (see Tables 3-1 and 3-2) included pitch carbon phenolic candidate throat materials, and

silica and canvas phenolic candidate exit cone materials. A major part of the screening program was

devoted to the pitch carbon phenolics since these materials show promise for very significant reduc

tions in material costs.

The screening test conditions were designed to simulate the actual motor firing conditions as

closely as possible. Since the major emphasis was the thermal performance of a meterial in a rocket

nozzle, simulation of the following parameters was considered important:

• Heat flux to the material (q)

• Reactive chemical species (H, 0) composition

These two parameters were chosen because the former represents the simulation of in-depth temperature

profile and the latter represents the simulation of surface chemical erosion. An exact simulation

would, of course, not be possible so some c~mpromises were necessary for testing in an arc plasma gen

erator. Tables 3-1 and 3-2 show the comparisons between the screening test conditions and anticipated

motor firing conditions.

Low cost materials were tested in the APG in a planar nozzle configuration (see Figure 3-1).

As can be seen two samples can be tested simultaneously. Due to supplier difficulties, not all of

the materials selected for screening tests were received in time. The screening tests were there

fore performed in two series. Series I screening tests were performed with the composite plies in

the 0 degree orientation for exit and molding compound materials and 90 degree orientation for

throat materials. Continuous filament pitch carbon phenolic material (Series II) was tested in the

90° orientation with a dummy model on the opposite wall. These dummy models were fabricated from

the same materials but plies were oriented at 20° rather than 90°. A tentative selection of

materials for full characterization was made based on the first screening test series.

3-1

TABLE 3-1. COMPARISON OF ROCKET MOTOR AND APG ENVIRONMENTS

Rocket Motor Convective Environment

A >. Pe ue he peueCH qA* (ft) (atm) (ft/see) (Btu/1bm) (1bm/ft2 -see) (Btu/ft 2 -sec)

1.0 3.1 26 3430 595 0.78 1170

3.0 7.8 3.2 7050 -190 ·.21 277

4.0 9.6 2.2 7440 -320 .15 265

ARC Plasma Generator Environment

A Pe he peueCH qcwA* (atm) (Btu/1bm) (lbm/ft2-see) (Btu/ft2-see)

1.0 2.93 8713 0.074 982

3.0 1.82 2456 .042, 281 .

4.0 1.76 2558 .037 250

TABLE 3-2. COMPARISON OF APG TEST GAS AND TYPICALNOZZLE EXHAUST GAS EQUILIRBIUM COMPOSITION

Test Gas Equilibrium Composition

Typical Nozzle Exhaust Gas H, C, 0 Equilibrium Composition

3-2

W I W

,08

4-0

OG

slo

eP

Lb

lTE

MO

DIF

ICA

TIO

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4-0

0,

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Figu

re3-

1.T

est

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igur

atio

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70

84

-00

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In the Series I tests, the throat entrance insert ("C" section) was fabricated from pyro1ytic

graphite. Very little ablation was observed on this section so that subsequent Series II testing was

done using P03 graphite throat entrance inserts. However, as a precaution, the inlet end of the throat

test section was increased to minimize any possible effects due to material discontinuities. The test

configurations for both Series I and II are shown in Figure 3-2 and the test matrix is shown in Table

3-3. As can be seen, materials from the same generic class were arranged to be tested simultaneously

on the premise that their performance should be similar.

The screening test results are shown in Tables 3-4 and 3-5 respectively for pitch and silica

reinforced material. As can be seen, the ablation performance of the selected low cost materials for

tha Shuttle SRM throat were all comparable to the baseline material, rayon carbon cloth phenolic.

In fact, some materials appeared to be even superior to rayon precursor carbon cloth phenolic. Some

similarity in ablation performance is expected because the thermal and physical properties of the test

ed materials were of the same order of magnitude (see Table 2-1), however superior performance was an

unexpected benefits. Typical post-test surface conditions for some APG screening test samples are

shown in Figure 3-3 to 3-5.

The screening test results for Shuttle SRM exit cone materials indicate that (see Table 3-5)

double thick silica cloth phenolic had the best ablation performance among the silica cloth phenolic

materials. The reason for this superior performance is not clear because no correlation was found

based on the material properties. Canvas cloth phenolic has poorer performance compared to silica

cloth phenolic. The reason here is obvious; canvas cloth phenolic has higher hydrogen and oxygen

contents which result in a higher degree of thermal decomposition.

Also shown in Tables 3-4 and 3-5 are the residual volatiles content for the cured composites

tested in Series I. These measurements were made by Hexcel Corporation.

From the screening test results, five generic materials were selected for full thermophysical

property characterization. Of these five, four were selected from the throat material category and

one from the exit cone material category. Since the main objective of this program was to study low cost

materials, the selection was based on ablation performance as well as cost performance. Cost perfor

mance here is defined as total ablation times material cost per pound. During the first round of

selection, one representative material from each generic title was selected based on ablation perfor

mance. On the second round of selection, a comparison of cost performance among the representative

materials was made (see Tables 3-6 and 3-7), and the five materials were selected accordingly.

3-4

Screening Test Series 1

A,,,,,L::-L 1.0

--I 1.25

Screening Tests Series 2

2.25II-A

1.619I-B

cl",',~ 2.17

--J

Figure 3-2. Screening test sample dimensions.

3-5

TABLE 3-3. SCREENING TEST MATRIX

Series Test Model Description OrientationNo. (Deg. )

I 2524 FM5782MC MXC313P 0

2525 4CSP08MC ACS-C86PMC

2530 4CSP08MC ACS-C86PMC

2534 MX2600 CA-2221

2535 MX2600 MXSE-55

2536 MX2600 4K9502

2537 MX2600 MXKF-418

2541 MX4926 ACX-C86PM 90

2542 ACX-C86K ACX-C861C

2543 XFM5795 ACX-CPH

2544 MX-4929 FM5782BG

2545 4CSP08/4C1008 MX4926

2546 MX4928 FM5790

II 1 DUMMY 4C1246 900

DUMMY FM5795 90 0

DUMMY MXG1033FMC 900

3-6

TABLE 3-4. SHUTTLE SRM THROAT MATERIAL SCREENING TEST RESULTS

Material Volatile 2 Mass 3

SurfaceGeneric Title Source Content LossDesignation (%) (Grams) Appearance

Rayon Cloth Fiberite MX4926 0.56 5.2 SmoothCloth Phenolic

Pitch Mat Fiberite MX4929 1.30 4.9 SmoothCarbon Phenolic U.S. Polymeric FM5782BG 2.05 4.4 Smooth

Ferro ACX-C86PM 1.38 5.0 Smooth

Hybrid Pitch Fiberite MX4928 1.70 4.8 RoughMat/Rayon U.S. Polymeric FM5790 2.81 4.0 Rough

Cloth Phenolic Hexcel 4CSP08/4C1OO8 1.47 5.3 Rough

Kynol Carbon Fiberite XFM5795 5.41 3.6 SmoothCloth Phenolic Ferro ACX-CPH 1.46 3.3 Smooth

Kureha Pitch Ferro ACX-C86K 4.04 5.8 RoughCarbon Cloth

Phenolic

Pitch Mat 1 Fiberite MXC-3l3P 1.08 5.7 Spa 11 edMolding Compound U.S. Polymeric FM5782MC 1. 76 6.8 Spalled

Hexcel 4CSP08MC 1. 69 6.6 Spalled

Kureha Pitch l Ferro ACX-C86KMC 2.33 4.1 RoughFabric Molding

Compound

Pitch Carbon Fiberite MXC1033F 3.80 (~ )Cloth Phenolic U.S. Polymeric FM5795 5.41 4.6

Hexcel 4C1246 5.2

UC Pitch Fabric Fiberite MSG1033FMC 6.4 RoughMolding Compound

lFabric plies were oriented 90° to the heated surface except for these materials.For these materials, the heated surface was perpendicular to the molding direction.

2Cured composite

3Normalized to 30 seconds and Series I configuration

~APG malfunction

3-7

W I 00

TABL

E3-

5.SH

UTTL

ESR

MEX

ITCO

NEM

ATER

IALS

SCRE

ENIN

GTE

STRE

SULT

Sl

Vol

atil

eM

ass

Sur

face

Mat

eria

lC

onte

ntLo

ssG

ener

icT

ftle

Sour

ceD

esig

natio

n(%

)(G

MS)

App

eara

nce

Stan

dard

Sn

ica

Fib

erit

eM

X260

04.

192.

6Si

02an

dSi

CC

loth

Phen

olic

Fonn

atio

n

Snap

wra

pS

ilic

aF

iber

ite

MXS

E-55

1.83

3.6

Si02

and

SiC

Clo

thPh

enol

icFo

nnat

ion

Dou

ble

Thi

ckS

ilic

aC

loth

Ferr

oC

A-2

221/

962.

221.

8Si

02an

dSi

CPh

enol

icFo

nnat

ion

Can

vas

Clo

thF

iber

ite

MXK

F-41

84.

125.

1S

igni

fica

ntPh

enol

icH

exce

l4K

9502

4.26

6.2

Cha

rrin

g

lAll

test

sco

nduc

ted

inth

e0°

ply

orie

ntat

ion

with

resp

ect

toce

nter

line

2Non

naliz

edto

30se

cond

s

'& \Xl

......~

4C10

08MX

4928

W I ~

MX49

26FM

5790

Fig

ure

3-3.

Typ

ical

po

st-f

ired

surf

ace

cond

itio

no

fhy

brid

carb

on/p

heno

lic

mat

eria

ls.

W I ......

a

~ <:::>~ ~

t~x

4926

ACX-

C86P

M

1

MX49

29

FM57

82BG

Fig

ure

3-4.

Typ

ical

po

st-f

ired

surf

ace

cond

itio

nof

pitc

hm

at/p

heno

lic

mat

eria

ls.

W I --'

--'

~ 0'

~

j

ACX-

C86K

XFM

5795

ACX-

686K

ACX-

CPH

Figu

re3-

5.T

ypic

alp

ost

-fir

edsu

rfac

eco

ndit

ion

of

carb

onfa

bri

c/p

hen

oli

cm

ater

ials

.

W I N

TABL

E3-

6.SH

UTTL

ESR

MTH

ROAT

MAT

ERIA

LSPE

RFOR

MAN

CEAN

DCO

STCO

MPA

RISO

NS

Nom

inal

iNo

mina

lM

ass

Raw

Mat

eria

lM

ass

Loss

xRa

wM

ater

ial

Gen

eric

Tit

leD

ensi

tyC

ost

(197

5$I

lb)

Cos

tPe

rfor

man

ce(G

MS

x$

/lb

)(G

M/C

C)Lo

ss;

(GM

)19

7519

8019

7519

80

Rayo

nC

arbo

n1.

405.

230

.030

.015

615

6C

loth

Phe

noli

c

Pit

chM

at1.

454.

815

.012

.072

58Ca

rbon

Phen

o1ic

Hyb

ridP

itch

Mat

/Ray

on1.

454.

722

.521

.010

699

Clo

thP

heno

lic

Kyn

olC

arbo

n1.

493.

525

.030

.088

105

Clo

thP

heno

lic

Kur

eha

Pit

chCa

rbon

Clo

th5.

8P

heno

lic

Pit

chM

atM

oldi

ng1.

536.

315

.512

.598

79Co

mpo

und

Kur

eha

Pit

chF

abri

cM

oldi

ng1.

404.

1Co

mpo

und

UCP

itch

Fab

ric

Mol

ding

Com

poun

d6.

428

.023

.017

914

7!

(.o

JI -"

(.oJ

TABL

E3-

7.SH

UTTL

ESR

MEX

ITCO

NEM

ATER

IALS

PERF

ORM

ANCE

AND

COST

COM

PARI

SONS

Nom

ina1

Nom

inal

Raw

Mat

eria

lM

ass

Loss

xRa

wM

ater

ial

Gen

eric

Tit

leD

ensi

t)M

ass

Cos

t(1

975

$/lb

)C

ost

Perf

orm

ance

(GM

Sx

$lb)

(GM

S/CC

Loss

(GM

S)19

7519

8019

7519

80

Sil

ica

Phen

olic

1.74

2.6

610

1626

Snap

wra

p1.

303.

66

1022

36S

ilic

aPh

enol

ic

Dou

ble

Thi

ck1.

751.

86

1011

18S

ilic

aPh

enol

ic

Can

vas

1.25

5.6

55

2828

Phe

noli

c

The final selection of low cost materials for further study is shown in Table 3-8. With the

exception of MXG1033F and 4K9502, these selected materials have shown good ablation performance and

low cost potential. MXG1033F was selected arbitrarily since no screening test data was obtained for

this material class. Silica phenolic is an obvious exit cone material; however low cost silica mate

rials are very similar to those that have been previously characterized. Canvas phenolic was there-

fore selected as an exit cone material for full characterization. Canvas cloth phenolic has a

reasonable low cost potential although quality control and material traceability leaves something to

be desired.

TABLE 3-8. SELECTION OF SHUTTLE SRM LOW COST NOZZLE EVALUATION MATERIALS

Generi c Ti t1 e Source MaterialDesignation

Pitch Fabric Carbon Fiberite MXG 1033FPhenolic

Pitch Mat Phenolic Hexce1 4CS P08

Hybrid Pitch MatiRayon Fabric Carbon U.S. Polymeric FM 5790

Phenolic

Pitch Mat Phenolic Fiberite MXC 313PMolding Compound

Canvas Cloth Hexce1 4K 9502Phenolic

3-14

SECTION 4

INTERMEDIATE TEST PROGRAM

In the low cost materials screening test, five generic materials (see Table 3-8) were selected

for further evaluation. Both 20° and 90° composite ply orientation tests were performed on each of

the five intermediate test materials. In addition, some materials were subjected to an extended cure*

to determine whether or not this would affect the ablation performance.

The intermediate test matrix is shown in Table 4-1. The test configuration was the same as

Series II of the screening test program.

TABLE 4-1. INTERMEDIATE TEST MATRIX

CARBON PHENOLIC, A/A* = 1.090° orientation

20° orientationMXG1033 A.R.FM5790 A.R.MXC313P A. R.4CSP08 A.R.

CANVAS PHENOLIC90° orientation

MXG1033FFM5790MXC3l3P4CSP08

A.R.*A.R.A.R.A.R.

MXG1033F P.C. tFM5790 P.C.MXC313P P.C.4CSP08 P.C.

MXG1033F P.C.FM5790 P.C.MXC3l3P P.C.4CSP08 P.C.

4K9502 A.R. 4K9502 P.C.20° orientation

4K9502 A.R. 4K9502 P.C.

*As received material

tPost-cured material

*To be referred to as post-cured material.

4-1

The intermediate test results are shown in Table 4-2.

TABLE 4-2. SHUTTLE SRM EVALUATION MATERIALSINTERMEDIATE TEST RESULTS 1

20°2 90°2Generi c Titl e Source Material Mass Mass A/A*3Designation Loss Loss

(GMS) (GMS)

Pitch Mat Hexcel 4CSP08 2.9 4.8 1.0Carbon Phenolic

Hybrid PitchMat/Rayon USP FM5790 2.5 4.5 1.0Fabric Phenolic

Pitch Fabric Fi beri te MXG1033F Test Faci 1i ty 1.0Phenolic Fa il ure

Pitch Mat Fiberite MXC3l3P 2.6 6.0 1.0Molding Compound------

Canvas Phenolic Hexcel 4K9502 4.6 5.2 4.0

lAll tests conducted in both the 20° and 90° ply orientation2Normalized to 30 seconds and initial screening configuration,

material as received3Simulated Shuttle SRM nozzle expansion ratio

No delamination was observed in the 20° orientation for both cured (as received) and post-cured

materials. It was also found that the post-cured materials (except for pitch mat molding compound)

perform slightly better than the as-received materials (see Figures 4-1 and 4-2). The better perfor

mance is probably due to lower volatile and water contents in the post-cured materials since these

two elements would induce exothermic reactions and chemical erosion at the surface. The results of

the 90° orientation as-received materials did not provide any new information, but do provide as

surance that materials to be fully characterized have a reproducible thermal performance:

The following conclusions can be extracted from this study.

• Intermediate test data are consistent with screening test data.

• The tests provided assurance that materials to be fully characterized are reproducible.

• Post-cured materials have better ablation performance than as-received materials.

• The results indicate that full characterization tests should be performed on post-cured

materials.

4-2

-l'> I W

...J~ ..... c:r

:w i l

V') w I-

200

PLY

ORIE

NTAT

ION

TEST

ING

POST

-CUR

EI

HYBR

IDPH

ENOL

IC

CURE

HYBR

IDPH

ENOL

IC

POST

-CUR

EPI

TCH

ICA

RBON

MAT

.M

.C.

CURE

PITC

HCA

RBON

MAT

.M

.C.

+-POST

-CUR

E4

SILI

CAPH

ENOL

IC,

~__1

4---C

URE

SILI

CAI

PHEN

OLIC

POST

-CUR

EI

CANV

ASPH

ENOL

IC

CURE

CANV

ASPH

ENOL

IC

II

II

II

r-. o 0:> I «

o0.

10.

20

.30.

40.

50.

6

MASS

LOSS

RATE

(GM

S/SE

C)

Figu

re4-

1.C

ured

vers

uspo

st-c

ured

inte

rmed

iate

test

resu

lts.

900

PLY

ORIE

NTAT

ION

TEST

ING

+:> I +:>

-J co: .... ex:

UJ

~ :E: tn UJ

I-

POST

-CUR

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HYBR

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IC

CURE

HYBR

IDI

PHEN

OLIC

POST

-CUR

EPI

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MAT

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H

ICA

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MAT

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URE

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CURE

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PHEN

OLIC

POST

-CUR

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CANV

ASPH

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CURE

CANV

ASPH

ENOL

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II

II

.t\ o CO I <l:

a0.

10.

20

.3

MASS

LOSS

RATE

(GM

S/SE

C)0.

40.

5

Figu

re4-

2.C

ured

vers

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ured

inte

rmed

iate

test

resu

lts.

SECTION 5

MATERIALS FULL CHARACTERIZATION PROGRAM

Since the properties for charring ablative materials are dependent upon fabric orientation

and thermodynamic state (T and p), material properties were evaluated for virgin and charred com

posites in at least two fabric orientations. The properties determined were

• Decomposition kinetics

• Elemental composition

• Heat of formation

• Density

• Specific heat capacity

• Thermal conductivity

The materials for which these properties were determined are

• U.S. Polymeric

• Fiberite

• Hexce1

• Fiberite

• Hexce1

5.1 DECOMPOSITION KINETICS

FM5790

MXG1033F

4K9502

MXC313P

4CSP08

Resinous materials degrade in a highly complex manner. These complex degradation mechanisms

are generally not understood sufficiently to formulate exact analytical expressions. Therefore,

empirical homogeneous kinetics are normally used to describe the degradation.

5-1

The thermal degradation reactions, if assumed to be irreversible, may be described by a psuedo-

order classical rate expression.

(_Eai\ (Pi _ Pri\ 1/Ji

RTJ POi POi j (5-1 )

The kinetic parameters (activation energy Eai , frequency factor Bi , and reaction order 1/Ji) can be

determined by reducing thermogravimetric analysis (TGA) data.

The multiple-linear-regression analysis is one of the procedures which can be used to reduce

TGA data. This analysis has the capability to evaluate the three kinetic parameters simultaneously

and also to curve fit the input data in a theoretically optimal manner.

The evaluation procedure is straightforward. Equation (5-1) is first linearized to yield

the following form

JI, ( d Pi/POi) - Jl,n B. +~ (1) + ,10. Jl,n(Pi - Pri\n - de - , R \T '1', \ POi J (5-2)

The bracketed terms in Equation (5-2) can be obtained from TGA data. As the number of data points

is larger than three, the equations will overdetermine the values of kinetic constants. Hence, an

optimum curve fitting procedure is required. If we write Equation (5-2) in matrix notation, it has

the form

B= AX (5-3)

where B and A are matrices whose elements are determined from the TGA data and X is the matrix of

best fit parameters. The curve fitting procedure is then applied by multiplying Equation (5-3) by

the transpose of A

(5-4)

where ATA is square and determinate. Hence, the Xmatrix can be evaluated by Gaussian elimination

from the transformed normal equations.

The experimental data used for data reduction are obtained from thermogravimetric analysis

(TGA). TGA is an experimental procedure to measure the pyrolysis mass loss history at a prescribed

heating rate. The heating agent is usually an inert gas such as argon or nitrogen in order to pre

vent any surface chemical reaction. Heating rates may range from O.l°C to lOO°C per minute. For the

5-2

low cost materials, a heating rate of 10°C per minute was used to obtain TGA data since the higher

the heating rate, the lower the accuracy of the data. 10°C per minute is a value that has yielded

reliable data in the past. In addition, the pyrolysis kinetics of charring materials behave

almost linearly with respect to heating rate. The experimental data was obtained by a subcontract

to The Boeing Company.

The kinetic constants which were determined for the low cost materials are presented in

Table 5-1. Equation (5-1) was integrated to reproduce TGA results. Excellent agreement was

achieved which indicates the quality of the correlated kinetic constants (see Figures 5-1 to 5-5).

5.2 ELEMENTAL COMPOSITION

The elemental composition of the pyrolysis gas and char must be known in order to generate

surface thermochemistry tables and determine the pyrolysis gas enthalpy. The char composition for

canvas and carbon phenolic materials is often easy to determine as it is merely carbon residue. To

determine the pyrolysis gas composition, however, requires a knowledge of both the virgin material

composition and the residual mass fraction. The virgin material composition is usually provided by

the manufacturers, and the residual mass fraction is known from TGA. With this information,

the elemental composition of pyrolysis gas can then be evaluated by the following equations:

=~KpYi 1 - r (5-5)

(5-6)

where K is the mass fraction; r is the residual mass fraction; and subscripts py, c, v denote py-

rolysis gas, carbon, and virgin material, respectively.

The evaluated pyrolysis gas elemental compositions of the low cost materials are presented

in Table 5-2.

5.3 HEAT OF FORMATION

The virgin material heat of formation is determined from

(5:"7)

5-3

TABLE 5-1. DECOMPOSITION KINETICS OF LOW COST MATERIALS

Material Reaction POi Pri BiWi Eai/R rNo. i (lbm/ft 3) (lbm/ft 3) (sec-I) (OR)

FM5790 1 2.375 0 4.8 0.358 7787.6 1.0

2 19.135 75.560 3.5712 x 106 2.259 27825.0

3 - - - - -

MXG1033F 1 1.0226 0 6.4977 x 104 0.838 12095.0 1.0

2 101.2374 90.3949 2.09904 x 10 6 2.667 23372.0

3 - - - - -4K9502 1 6.622 0 5.9285 x 102 1.091 10096.0 0.5

2 88.906 0 2.39295 x 1011 1. 317 35602.0

3 81.048 51.206 2.37558 x 10 7 3.101 28225.0

MXC313P 1 2.4756 0 160.464 2.5591 8302.88 0.5

2 8.5764 0 4.884 x 10 9 1.2265 35541.80

3 165.7818 143.2356 1.70007 x 1022 6.9232 64876.00

4CSP08 1 1.8965 0 0.77715 0.91273 5522.17 1.0

2 79.6735 67.4994 7.791 0.96349 13005.18

3 - - - - -

5-4

~ ~ ...., ...., ~ , c:(

100Iii

)(M

,IIIIIa

&L:I

IFI

1579

0po

st-c

ured

•~

II

II

I. T

=10

°Cjm

;n_

__

data

)(pr

edic

tion

-- ~I0I

I»

I,

II

II

~_

II

II

r.-:R

01 I 01

80

'!

I!

I!

II

,!

!,

o20

040

060

080

010

0012

0014

0016

0018

0020

0022

0CTe

mp

-oR

Figu

re5-

1.C

ompa

rison

ofTG

Ada

taan

dCM

Apr

edic

tion

.

(Jl

I '"

100 90

---;;;

---80

~ :EI~

70

r.

r~

MXC

313P

Pos

t-cu

red

T

.~

. T-1

O°C

/min

""

Dat

a-

XP

redi

ctio

n

\

'-.

Lt> ..,. .., .., .....

. Ic:(

6040

060

080

010

0012

00

Tem

pera

ture

-oR

1400

1600

1800

2000

Figu

re5-

2.C

ompa

rison

ofTG

Ada

taan

dCM

Apr

edic

tion

.

<.n I ......

100 90

.-..

80~ 2£

:1:.:0

70

.I

4CSP

08P

ost-

cure

d.

~T

1OOQ

/min

Dat

a

~I-

)(P

redi

ctio

n

~\

10~ M M ~

I<C

6040

060

000

010

0012

00

Tem

pera

ture

-oR

1400

1600

1800

2000

Figu

re5-

3.C

ompa

rison

ofTG

Ada

taan

dCM

Apr

edic

tion

.

I"'

"."

I

MXG

1033

FP

ost-

cure

d. T

WO

C/m

in

Dat

a

XP

redi

ctio

n

!

~~.

..

c.n I ex>

100

--..

90~ :E

1::!:

o

BOo

200

400

600

BOO

1000

1200

1400

1600

1800

.......

'<!"

M M ~I

<t

2000

Tem

pera

ture

-oR

Figu

re5-

4.C

ompa

rison

ofTG

Ada

taan

dCM

Apr

edic

tion

.

01 I '"

100 90 30 70 60

-50

~ :E

I:E

40 30

--I

II

4K95

02P

ost-

cure

d.

.r"T

10°C

/min

t--

Dat

a

XP

redi

ctio

n.

~ .\ JIl )

.,

)

1

,

~ t")

t") I c:e

20o

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Tem

pera

ture

-oR

Figu

re5-

5.C

ompa

rison

ofTG

Ada

taan

dCM

Apr

edic

tion

.

TABLE 5-2. ELEMENTAL COMPOSITION OFPYROLYSIS GAS

Type of Mass Fraction

Material H C 0

FM5790 0.14727 0.46301 0.38972MXG1033F 0.19383 0.29337 0.512804CSP08 0.16766 0.38884 0.44350MXC313P 0.13526 0.50679 0.357954K9502 0.08880 0.40760 0.50360

The reinforcement material for the five selected low cost materials is either carbon or canvas.

The nominal values for resin and reinforcement heats of formation are shown in Table 5-3. For the

TABLE 5-3. NOMINAL VALUES FOR RESIN ANDREINFORCEMENT HEATS OFFORMATION

lIH -1083 Btull bmfC2H20

lIH -2569 Btull bmfcanvas

lIH o Btu/lbmfcarbon

char, the heat of formation again is just merely the carbon heat of formation, i.e., zero.

Table 5-4 presents the evaluated heats of formation of the virgin low cost materials.

TABLE 5-4. HEAT OF FORMATION OF VIRGINLOW COST MATERIALS

Type of Material lIHf (Btull bm)

4CSP08 - 487.35FM5790 - 476.52

MXG1033F - 379.05MXC313P - 433.204K9502 -1944.88

5.4 DENSITY

The virgin material density was determined by precise weight and dimension measurement of

samples which have regular geometric shapes. The char density is evaluated by multiplying the vir

gin material density by the residual mass fraction which was obtained from the TGA data.

5-10

The measured or evaluated densities are shown in Table 5-5.

TABLE 5-5. DENSITIES OF LOW COST MATERIALS

Materials Virgin Density Char Density(lbm/ft 3

) (lbm/ft 3 )

4CSP08 81.570 67.500FM5790 93.510 75.560MXG1033F 102.260 90.395MXC313P 88.417 71.61784~5~ 88.288 25.603

5.5 SPECIFIC HEAT CAPACITY

The specific heat of the virgin material was determined by graphical differentiation of spe

cific enthalpy versus temperature curves. The enthalpy was measured using an ice mantle calorim

eter. The calorimeter consists of a copper well. a distilled water vessel surrounding the copper

well, an ice bath surrounding the vessel, and an insulation filled container surrounding the ice

bath. An ice mantle is formed on the outer surface of the copper well.

The material sample is heated to the desired uniform temperature in a muffle furnace and

then dropped directly from the furnace into the calorimeter. The energy lost by the sample as it

cools results in a volume change in the distilled water due to the partial melting of the ice man

tle. This volume change is quantitatively related to the original energy of the sample. A small

leak inherent in the apparatus is calibrated after each test and accounted for in the data reduction.

The samples used in the calorimeter tests are approximately 0.02 cubic inch in volume.

Table 5-6 shows the evaluated virgin material specific heat as a function of temperature.

The char specific heat, however, need not be determined since the specific heat capacity of carbon

is known.

5.6 THERMAL CONDUCTIVITY

The material thermal conductivity was determined by two separate techniques. The applicabil-

ity of each technique is dependent on the temperature and state of the material. The conventional

technique is applicable for the virgin material over the temperature range from room temperature to

approximately 700°F. The dynamic technique is applicable for the virgin, partially charred, or

fully charred material over the temperature range from 700°F to approximately 4000°F.

5-11

<

TABLE 5-6. VIRGIN MATERIAL SPECIFIC HEAT CAPACITY

Materials Temperature Cp(OR) (Btu/1bm- OR)

4K9502 500 0.360

BOO 0.440

1000 0.500

1200 0.540

2000 0.540

6000 0.540

4CSP08 500 0.200

800 0.320

1000 0.400

1200 0.460

1400 0.500

2000 0.500

6000 0.500

MXG1033F 500 0.120

800 0.320

1000 0.380

1200 0.430

1400 0.440

2000 0.4406000 0.440

MXC313P 500 0.160

800 0.340

1000 0.380

1200 0.4201400 0.440

2000 0.440

6000 0.440

FM5790 500 0.160

800 0.360

1000 0.420

1200 0.420

1400 0.420

2000 0.420

6000 0.420

5-12

5.6.1 Virgin Material Thermal Conductivity

Virgin material thermal conductivity was determined using a small thermal conductivity cell.

In this apparatus, the testing sample (1/6" thick wafer) is sandwiched between an aluminum block

(0.75 x 1.25 x 1.50 inches), and an aluminum slab (0.25 x 1.25 x 1.50 inches). The temperature

difference (6T) is then measured across the testing sample as the block is heated at a linear rate

equal to 4°C/min.

For calibration, an aluminum wafer is placed in the cell. The resulting 6T is assumed to be

the temperature baseline. A wafer of fused silica is run as a reference sample, and an instrument

constant is calculated for each 100° interval. The comparative values are then calculated from the

expression:

(5-8)

where k is the thermal conductivity, C is the instrument constant, L is the wafer thickness, and

~T is the temperature difference across the wafer.

Figures 5-6 to 5-10 present the measured thermal conductivity at both 0° and 90° orientation

for the virgin materials.

5.6.2 Dynamic Thermal Conductivity

The dynamic thermal conductivity technique is a combined experimental and analytical technique

which has the inherent advantage that the char characteristics of the materials are accurately du

plicated. This technique has been described in detail in References 2 through 5, and thus, will

only be summarized in the paragraphs below.

The analysis portion of this procedure involves solving the governing equation for transient

one-dimensional heat conduction in a charring ablating material. Incorporated within this equation

is the model for defining the thermal conductivity of the partially-charred and fully-charred mate

rials. This model is represented by the equation

k = (1 - x) k + xkP v (5-9)

where X is the mass fraction of virgin material and kp and kv are the thermal conductivities for

virgin and charred materials, respectively.

5-13

o0\

<:t

(Y')

(Y') I ct:

I

MXG

1033

F(v

irgi

n)•

090

°· ·

IfA

0°

E20

0 I-.

--

----.:.

I-

-.

.:.-

-.... .

I.

,--

....·

I.:.

I,

II

.A

A·

..:..

..:.

·-

I 070

080

090

010

0011

0012

001

100

140

o

2.0

3.0

5.0

1.04.0

u Q)

III I

0:: °I +'

'+-

........ ::> +'

C!l

~

I 0 X I >,

+'

.~ >

.~

<.n

+'

I

U

~

::>

.j::

>

"'0 C 0 U 0 E S-

Q)

..c:.

I-

Tem

pv

oR

Figu

re5-

6.M

easu

red

virg

inm

ater

ial

ther

mal

cond

ucti

vity

.

o U")

M M ~I

<C o

UI

TM

XC31

3P(v

irg

in)

ogo

g

&00

0Q

200

0

.-f:)

-.V

n~

v

Ir;

......

-Q

~A

/\

A~

..:...

_.yo

&~

0 n 600

700

800

900

1000

1100

1200

1300

14

5.

u ClJ

4.el

l I~ 0

I ...., '+- ....... =" ...., co

~3.

I 0 X I >,

Ul

....,I

.-~

>2.

Ul

.- ...., u =" "0 c::

:0 u 0 E ~ CL

J1

..c f-

Tem

p-

oR

Fig

ure

5-7.

Mea

sure

dvi

rgin

mat

eria

lth

erm

alco

nduc

tivi

ty.

5.0

li:4.

0<

II I0

:: ° I ..... .... ......

:::> ..... GO

3.0

... I 0 .- X I >,

..... .~2.

00'

1

.....I

U~

:::>O

'l

"0 <:

0 u ~ ~ ~1.

0I-

I

Fr15

790

(vir

gin)

<:>90

°

A0°

EJ20

°

t:\

,\:I

c:>

~

-J:\

.-

'-

.:.

I~I

-I

II

AI

---I.p

~~

I-~

Ll'l

M M

I<t

:

o 600

700

800

900

1000

Tem

p-

OR11

0012

0013

0014

00

Figu

re5-

8.M

easu

red

virg

inm

ater

ial

ther

mal

cond

ucti

vity

.

N U'>

M M ~I

<C

1400

1300

1200

1100

1000

Tem

p-

oR90

080

070

0

I

4CSP

08(v

irgi

n)

<.:>90

°

A0°

I:l20

°

- " --

~" -

~

-

C.:.

.

I.:..

II

-"I

II

At.

AA

.:..

---

---

----

~--

-o 60

0

5.0

u ~4.

0I ex: °I ...., .... "~ ...., co ~

3.0

I 0 X I >,

01

....,I~

>....

:;;2.

0u ~ "'0 <:

0 u 0 E ~ ClJ t:=

1.0

Figu

re5-

9.M

easu

red

virg

inm

ater

ial

ther

mal

cond

ucti

vity

.

M I.t'l

M M ~I

c:(

1400

1300

1200

900

1000

1100

Tem

pera

ture

-oR

800,

700

I

4K95

02(v

irgi

n)

G>90

°

&.

0°

I!J20

°

I l

-.-

.:.~

.I

,I

-I

.I

)

--[)

-~--

...

o 600

1.03.0

2.0

5.0

4.0

U <II

VI I '" °I ... .... ......

::l ... CO " I 0 OX I >, ... .~ >

.~

0"1

...I

U

~

::l

ex>

"I: 0 U 0 E s.. <II

.s::~

Figu

re5-

10.

Mea

sure

dvi

rgin

mat

eria

lth

erm

alco

nduc

tivi

ty.

The analytical procedure for defining the thermal conductivity of in-depth charring materials in

volves solving the governing one~dimentional conservation of energy and mass equations for an im-

pressed surface boundary condition. The flux terms considered in these equations are illustrated

in Fi gure 5-11.

" ~our < ,'" '" '" '" '" ~..,~

I......,.--J--_--._...,.-..,..-.,....~_c:r

Figure 5-11. Control volumes for in-depth energy and mass balances.

If it is assumed that the pyrolysis gases do not react chemically with the char and the py-

rolysis gases pass immediately out through the char, then the conservation of energy equation

becomes

(5-10)

where

A- area

h - total material enthalpy (chemical plus sensible)

hg - total pyrolysis gas enthalpy

rng - pyrolysis gas flowrate

t - time

T - temperature

y - distance from surface

p - density

and the conservation of mass equation becomes

~\ d)\dY 7t = A '!/fJY

(5-11 )

5-19

The first term in Equation (5-10) accounts for the change in energy stored within the element, the

second term accounts for the net thermal heat conduction across the element, and the third term ac

counts for the net transfer of thermal energy due to the flow of pyrolysis gases. Equation (5-11)

describes the degradation of the material. The decomposition rate (op/ot)y is defined as an Arrhenius

type expression of the form

where

B - pre-exponental factor

Ea - activation energy

R- gas constant

Pp - original density

Pc - residual density

W- density factor exponent

3 )~.

L -E ./RT (Pi - PCi 1- B.e a1 p.. 1 p1 Ppi1=1

(5-12)

For most materials, it is sufficient to consider three different decomposing constituents, two

describing the resin and one describing the reinforcement. Equations (5-10) through (5-12) are

solved by the CMA program which is described in detail in Reference 1.

If the following material thermal and chemical properties are known

• Virgin and char specific heat

• Virgin thermal conductivity

• Virgin and char density

• Resin mass fraction

• Virgin and char heat of formation

• Decomposition kinetics of the resin system

then Equations (5-10) through (5-12) can be solved for the thermal conductivity by using measured

in-depth and surface transient temperatures. The method for obtaining the in-depth and surface

temperatures is described in the following paragraphs.

5-20

The thermal conductivity test samples were tested in the Aerotherm 1 MW APG. The APG is

shown schematically in Figure 5-12. The test gases and test conditions were chosen to yield a

material thermal response typical of that in the actual application of interest. In addition,

chemically inert test gases were used so that the surface recession due to chemical corrosivity is

zero. Therefore, this surface boundary condition which is required in the data reduction process

was accurately known. The selected test gas, which is shown below, is chemically inert to most

materials at high temperatures and also approximates the specific heat capacity of rocket motor com

bustion products (Reference 2).

Mass Fraction0.2236

0.7764

The test configuration used was a two-dimensional (2-D) supersonic nozzle in which the con-

ductivity test section formed one wall as shown in Figure 5-13. The measurement station was the

nozzle throat which is of finite length and yields a significant region of well-defined, constant

test conditions. The 2-D configuration allowed the test section to be obtained from parts fabricated

by representative techniques (e.g., tape wrapped at any layup angle), allowed an accurate thermo

couple instrumentation technique, and provided an approximately one-dimensional heat flux path.

The surface temperature boundary condition was measured continuously during each test with an

infrared optical pyrometer. The in-depth temperatures were measured continuously during each test

at four locations and, together with the measured surface recession and surface temperature, provided

the test results on which the calculation of thermal conductivity was based. Tungsten-5 percent

rhenium thermocouples were used for temperature measurements at the two locations nearest the surface.

Chromel/alumel thermocouples were used at the other locations. The thermocouple installation tech

nique is illustrated in Figure 5-13. The stepped hole which accepts the thermocouple provides inti

mate contact with the material. The thermocouple wires were brought down the side walls through

alumina sleeving to prevent shorting across the electrically conductive char and/or virgin material.

The thermocouple wire size, compatible with the capabilities of thermocouple hole drilling, was

0.005 inch. The nominal thermocouple depths were 0.075, 0.150, 0.250, and 0.400. The actual thermo

couple depths were accurately determined from x-ray negatives. The details and techniques for

drilling the stepped hole and for thermally instrumenting the model are presented in Reference 3.

Since delamination is likely in 0° orientation testing, this experiment was conducted in

the 20° and 90° orientations.

5-21

01 I N N

TU

NG

ST

EN

CA

THO

DE

CA

THO

DE

MO

DU

LE

20

NO

ZZ

LE

TE

ST

SE

CT

ION

AX

ISY

MM

ET

RIC

TO

20

T

RA

NS

ITIO

NS

EC

TIO

N

Figu

re5-

12.

Aer

othe

rmco

nst

rict

or

are,

rock

etsi

mul

ator

conf

igur

atio

n.

ClJ<::~oa..~

=> ....,0'"u~

o~

E'"~....,

ClJl/l.£:: <::I-'~

5-23

c0, .~....,UQ)

:;, III

....,

"-\ IIIClJ....,3:0:;:....,U=>

""(lJ....,<::(lJE=>~....,III<::.~

~

It!u.~

a.~

M~

ILO

(lJ~

=>Ol.~

LJ...

The following equation was then applied to back out the 0° orientation conductivity after conducti-

vities in the 20° and 90° orientations were evaluated.

The evaluated char conductivities for 0° and 90° orientation are shown in Figures 5-14 and

5-15. The accuracy of the calculated char conductivity can be judged by comparing the calculated

and measured in-depth temperature histories (see Figures 5-16 through 5-25). Except for a few anom

alies the comparisons are excellent for the first 30 seconds of the tests. Subsequently, the pre-

dictions deviate from the measured values. This deviation was due to heat losses to the water

cooled APG components so that no attempt was made to match this data.

Post test char depth profiles are shown schematically in Figure 5-26. Differences in char

penetration between 20° and 90° orientation are obvious as are the effects of sidewall cooling. The

canvas phenolic material exhibited very erratic data and shows a correspondingly poor char profile,

especially for the 20° orientation. Of the data presented in Figures 5-14 and 5-15, the canvas

phenolic has the lowest confidence level.

The anomalies are due to thermocouple breakage or a separation of the thermocouples from the

char. The latter would result in very erratic temperatures which, for instance, were observed for

canvas phenolic (4K9502).

5.7 CHARACTERIZATION SUMMARY

The full characterization data is summarized in Tables 5-7 through 5-11. These tables pro

vided the information required for a thermal analysis of low cost materials.

5-24

40 r------r----~---...,..----r----.....,..----l./') l./')MM~

Ico:

30 t-----+----t-----J----+----+---,A

600050002000 3000 4000Temperature - oR

1000

10 t-----j-----+--

a:::°IUC1JVII~........... 20::J~c:l

...0

x~

Figure 5-14. 0° char thermal conductivity.

5-25

40 ...------.....~.+----_+----t__---+---~

Layup angle90°

4K950230

c:::

°IUQJIIII........

.......:>....coC' I1XG1033F"C> 20x

-'"

10 t------l~---_+--

6000500040003000200010000 ...--.........-------.....-------.....----o

Temperature 'V oR

Figure 5-15. 90° char thermal conductivity.

5-26

60.0o-r----r-----r---~.....--_Test 2785Model 7084-091'MXG1033FPost-cure 900

50.00

Surface

40.00N0.-0::0

TC2Q) 30.00lo-~ TCl.,'"lo-Q)0-s:Q)r-

20.00 CMA Prediction

~TCl

~ 2

8 3

10.00 0 4

80.000.001~---...---~--....I.---....

0.00 20.00 40.00 60.00Time - Seconds

Figure 5-16. Comparison of in-depth thermocouple measurementsand CMA prediction.

5-27

60.00r----.,.----..,..-----r----.....Test 2789I·lodel 7084-09514XG1033FPost-cure 200

50.001-----4------1-

coLt)....,....,....

I~

CllA PredictionTCl Ci.2~3840

TC2

TC3

Surface

10.00 __ Jr-, '.""1.

I 30.00...._--

a::o

OJs...:)....n:ls...OJ0SOJ

I- 20.00

'"o..

0.00 ~--~~~--.oIi!~~--~---...I0.00 20.00 40.00 60.00 30.00Time - Seconds


5-28

60.00r----"'T""'----r--=--~~----_Test 2736.ilode1 7084":092~'XC3l3P

Post-cure 900

50.00t----+----+----t----~

40.00N

0

:;

c:::0

TC2QJ~

='.... TC3ttl~QJQ.

EQJ TC4I-

CI1A PredictionTCl ~

2<:)3 B~0

O.O~-_~~_-~~-~~II'__-~0.00 20.00 40.00 60.00 80.00

Time - Seconds


5-29

60.00r----,..-----r-----r---.....

50.001---

Test 2788tlode1 7084-094tlXC313PPost-cure 200

i"-_"",_",,:,,...;s::u.:.rf~a:.:c.:.e., ------I

o\0..,..,....

Ic:e

40.00

~'"0;- A

6\ TC2c::0 &QJ 30.00 TC3~

~...,'"~QJ0-SQJI-

20.00

Ct1A Prediction

TCl Ili2~_

3840

o.OO~--~~--~~--~~__~0.00 20.00 40.00 60.00 80.00

Time - Seconds


5-30

60.00------,,---------.....----

Test 2793Model 7084-096low conditionPost-cure 900

50. 00 1- -+ +-=4~K9::..:5:.:::0.::.2_ __t_---__I

40.001------1-----+----+-----1

Surface

TC3

TC4

CtlA PredictionTC1 A2~

3 G.4 <:>

10. 00I--~~~~

0.00~_-~~~-_..~~--~~--~0.00 20.00 40.00 60.00 ao.oo

Time - Seconds

I 30.001-=- --1 -+ +- -1CIlI:::J+'IVICIlc..EQI

I- 20.001----

c::o


5-31

60.00 r----,..----r---......,.---....,

Test 2796Model 7084-0994K9502

50.00 I-- ~------------~ Post-cure 20°

N\0MM,....

I__.... e:t:

40. 00 t--..:...--+----+-----+----:-~No;-

30 00Surface

. t----~----'-=:__--+---_I

TC3

TC4·,-~~.;r~m Prediction

. & TC1~2

El 3o 4

0.00 ~--~~--~~--.......;;.--...I0.00 20.00 40.00 60.' 80.00

Time - Seconds

1o. 00 r::--",P

cv"~...,'""QJQ.EQJ

I- 20.00


5-32

60. oOr-----r---....,.---......---......Test 2784f10de1 7084-0904CSP08 .

50.O. -if- -+-P_~~t-cure 90°

1O. 0....,,,·.110...

Surface

CMA·Prediction.TC1A

2~

384Q

O.O~~_~~~_~~~_~A.. _0,00 20.00 40.00 60.;;:J 80.00

Ti me - Seconds

Figure 5-22. Comparison of in-depth thermocouple ~easurements

and CMA prediction.

5-33

60. 010y0__-""T"---""T"---""---~

Test 2795Model 7094-0984CSP08Post-cure 200

50.00

9F

40.00...o:;a:o

I 30.00CIl~~...,'"~CIl0ECIlI- 20.00

10.00

TCl

CMA Prediction&. TCl~ 28 3

o 4

80.0020.00 40.00 60.00Time - Seconds

0.00.... .... .... ... ....

0.00


5-34

60.0D-r---..,..---..,..---..,..----.

50.00

Test 2794Model 7084-097FM5790InstrumentPost-cure 90°

40.00

C1I30.00

s... TC3::s..../ISs...C1Ic.EC1II-

20.00

CMA Prediction

ATCl

~ 210.00 G 3

0 4

0.000.00 20.00 40.00 60.00 80.00

Time - Seconds


0::o

..o.-

5-35

10.00

60.00

Test 2787 In<0

Model 7084-093 MM

FM5790 ...I

Post-cure 200 <50.00

9F

40.00..0.- AAA&c:c: AI!:J.A0

30.00 TCl<IISo::l...'"So<IID-e<II.... 20.00

CMA Prediction8 TCl'0 28 3o 4

O.oO.~~-~~~-~~~_~~~_-!"'!'I10.00 20.00 40.00 60.00 80.00

Time - Seconds


5-36

0.0" virgin

4CSP08Pos t-cure 90°7084-090

ofr-..""M....J ..w-........~-'---L

MXG-1033FPost-cure 90°7084-091

0.0" virgin

MXC-313PP~st-cure 90°7004-092

f1.0" 0.0" virgin

FM5790Post-cure 20° I7084-093 --L'g 0.53"

1.0" --r-*-

virgin

MXC-313PPost-cure 20°

lW]7084.094-±.1.0" .--.-

-*-

virgin·

MXG-l033FPost-cure 20°7084-095 --*-T~ a.54"1.0" -,-

~

virgin

4K9502Post-cure 90°7084-096

t~J virgin

FM5790Post-cure 90°7084-097

~·a~ virgin

4CSP08Post-cure 20° l7084-098 ---l.-

'~. 0.5.0

11

1.0" t-*-

virgin

4K9502Post-cure 20°7084-099

0.0" virgin

-40"fFigure 5-26. Char layer profiles for char conductivity test samples.

5-37

<.T1

I W (Xl

TABL

E5-

7.TH

ERMA

LAN

DPH

YSIC

ALPR

OPER

TIES

OFPI

TCH

MAT

CARB

ONPH

ENOL

IC

Vir

gin

Mat

eria

lC

har

Nom

inal

Res

inR

ein-

The

rmal

Co

nd

uct

ivit

yT

herm

alC

on

du

ctiv

ity

Nom

inal

Res

inH

eat

of

forc

emen

tF

ail

Mat

eria

lD

ensi

tyM

ass

For

mat

ion

Ele

men

tal

Ele

men

tal

Tem

pera

ture

Sp

ecif

icx1

0'(B

tu/f

t-se

c-°R

)S

pec

ific

x10'

(Btu

/ft-

sec-

°R)

Form

ula

Tem

pera

ture

Em

issi

vit

yE

mis

siv

ity

Fra

ctio

nFo

nnu1

aH

eat

0090

0H

eat

00

900

(lb

/ft'

)(B

tull

bm)

(Ph

eno

lic)

(OR

)(O

R)

(Btu

/1bm

-OR)

layu

pla

yup

(Btu

llbm

-OR

)la

yup

layu

p

Pit

chM

at81

.570

0.17

2-4

87

.35

C 6H 6OC

~53

00

.20

01

.05

2.2

00

.85

0.21

02

.00

40.0

00

.85

Carb

onPh

enol

ic80

00

.32

01

.12

2.6

0-

2.0

04

0.0

0

1000

0.4

00

1.16

2.8

00

.43

02

.00

40

.00

4CSP

0812

000

.46

01.

222.

91-

2.0

040

.00

1400

0.5

00

1.2

5,2

.95

0.4

70

2.0

04

0.0

0

2000

0.48

42

.15

39

.40

3000

0.49

33

.10

36

.10

4000

0.49

84

.25

30

.50

5000

0.50

05

.75

23.2

0

a)T

hede

com

posi

tion

kin

etic

con

stan

tsfo

rp

hen

oli

cre

sin

are

tab

ula

ted

belo

w.

Rea

ctio

nPO

iP

riSi

'l>i

Eai

/Rr

i(l

bm

/ft'

)(l

bm

/ft'

)(s

ec-'

)(O

R)

11.

8965

00.

7771

50.

9127

355

22.1

7

279

.673

567

.499

47.

791

O.9

6349

1300

5.18

1.0

3-

--

--

b)T

hefo

llo

win

geq

uat

ion

issu

gg

este

dfo

rla

yup

ang

les

oth

erth

an0

0an

d90

0

{.(k

900

)}

k a=

k oo

1+

l<Qo""

"-1

sin

a

whe

ree

isth

ela

yup

ang

lere

fere

nce

dto

ata

ng

ent

toth

esu

rfac

e.

c}T

heco

nd

uct

ivit

yis

9ive

nby

k=

110kp

(T)

+(l

-x

)kc(

T)

whe

rex

isth

ev

irg

inm

ater

ial

mas

sfr

acti

on

,an

dk

and

k car

eth

ev

irg

inm

ater

ial

and

char

con

du

ctiv

ity

,re

spec

tiv

ely

.p

t.T1

I W \0

TABL

E5-

8.TH

ERM

ALAN

DPH

YSIC

ALPR

OPER

TIES

OFHY

BRID

PITC

HM

AT/R

AYON

FABR

ICPH

ENOL

IC

Vir

gin

Mat

eria

lC

har

Nom

inal

Res

inR

ein-

The

rma1

Con

duct

ivit

yT

herm

alC

on

du

ctiv

ity

,N

omin

alR

esin

Hea

to

ffo

rcem

ent

Fai

li

Mat

eria

lD

ensi

tyM

ass

For

mat

ion

Ele

men

tal

Ele

men

tal

Tem

pera

ture

Sp

ecif

icx

10

'(B

tu/f

t-se

C-°

R)

Sp

ecif

icx

lO'

(Btu

/ft-

seC

-°R

)I

Form

ula

Tem

pera

ture

Em

issi

vit

yE

mis

siv

ity

Fra

ctio

nFo

rmul

aH

eat

0°90

·H

eat

0°90

°(l

b/f

t')

(Btu

/lbm

)(P

hen

oli

c)(O

R)

(OR

)(B

tu/l

bm-O

R)

layu

pla

yup

(Btu

llbm

-OR

)la

yup

layu

p

Hyb

rid

Pit

ch93

.510

0.19

2-4

76.5

2C 6H 6O

C-

530

0.16

01.

032.

200

.85

0.2

10

0.3

014

.00

0.85

Mat

/Ray

on80

00.

360

1.2

32.

62-

Fab

ric

Phen

olic

1000

0.42

01

.30

2.75

0.4

30

FM57

9012

002.

77-

1600

0.4

70

2000

0.48

4

3000

0.49

3

4000

0.49

80

.40

13.7

5

5000

0.5

00

0.7

01

1.6

0-

a)Th

ede

com

posi

tion

kin

etic

con

stan

tsfo

rph

enol

icre

sin

are

tab

ula

ted

belo

w.

Rea

ctio

nPO

iP

riB i

1/Ji

Ea/

Rr

i(l

bm

/ft'

)(l

bm

/ft'

)(s

ec-'

)(O

R)

12.

375

04

.80.

358

7787

.6

291

.135

75.5

603.

5712

x1

0·

2.25

927

825.

01

.0

3-

--

--

'---

b)Th

efo

llow

ing

equ

atio

nis

sugg

este

dfo

rla

yup

ang

les

oth

erth

an0°

and

90°

k e=

koo{

l+(~

-l)s

ine}

whe

ree

isth

ela

yup

ang

lere

fere

nce

dto

ata

ng

ent

toth

esu

rfac

e.

c)Th

eco

nd

uct

ivit

yis

give

nby

k=

'xkp

(T)

+(1

-x)

kc(T

)

whe

rex

isth

ev

irg

inm

ater

ial

mas

sfr

acti

on

,an

dk p

and

k car

eth

ev

irg

inm

ater

ial

and

char

con

du

ctiv

ity

,re

spec

tiv

ely

.

U1 I ..,. o

TABL

E5-

9.TH

ERM

ALAN

DPH

YSIC

ALPR

OPER

TIES

OFPI

TCH

MAT

MOL

DING

COMP

OUND

Vir

gin

Mat

eria

lC

har

Nom

inal

Res

inR

ein-

The

rmal

Co

nd

uct

ivit

yT

herm

alC

on

du

ctiv

ity

Mat

eria

lN

omin

alR

esin

Hea

to

fE

lem

enta

lfo

rcem

ent

Fai

lx1

0"(B

tu/f

t-se

c-O

R)

x1

0'

(Btu

/ft-

sec-

OR

)D

ensi

tyM

ass

For

mat

ion

Form

ula

Ele

men

tal

Tem

pera

ture

Tem

pera

ture

Sp

ecif

icE

mis

siv

ity

Sp

ecif

icE

mis

siv

ity

Fra

ctio

nFo

rmul

aH

eat

0°90

°H

eat

0°90

°(l

b/f

t')

(Btu

/1bm

)(P

hen

oli

c)(O

R)

(OR

)(B

tu/1

bm-O

R)

layu

pla

yup

(Btu

llbm

-OR

)la

yup

layu

p

Pit

chM

at88

.417

0.19

0-4

33

.20

C 6H 6OC

-53

00

.16

01

.30

2.1

00

.85

0.2

10

3.6

511

.25

0.8

5[M

oldi

ng80

00

.36

01

.50

2.6

0-

Com

poun

d10

000

.42

01

.50

2.72

0.4

30

.M

XC3

13P

1200

-14

000.

470

2000

0.48

4

3000

0.49

34

.00

12.0

0

4000

0.49

85

.00

13

.90

5000

0.5

00

6.7

01

6.7

5

a)T

hede

com

posi

tion

kin

etic

con

stan

tsfo

rp

hen

oli

cre

sin

are

tab

ula

ted

belo

w.

Rea

ctio

nPO

iP

riB i

1/Ii

Eai

/Rr

i(l

bm

/ft'

)(l

bm

/ft'

)(s

ec')

(OR

)

12.

4756

016

4.46

42.

5591

8302

.88

28.

5764

04.

884

x1

0'

1.22

6535

541.

800

.5

316

5.78

1814

3.23

561.

7000

7x

10

"6.

9232

6487

6.00

b)T

hefo

llo

win

geq

uat

ion

issu

gg

este

dfo

rla

yup

ang

les

oth

erth

an0°

and

90°

k e=

koo{

l+(~

~~O

-l)

sin

e}

whe

ree

isth

ela

yup

angl

ere

fere

nce

dto

ata

ng

ent

toth

esu

rfac

e.

c)T

heco

nd

uct

ivit

yis

give

nby

k=

xkp

(T)

+(1

-x)

kc(T

)

whe

rex

isth

ev

irg

inm

ater

ial

mas

sfr

acti

on

,an

dk p

and

k car

eth

ev

irg

inm

ater

ial

and

char

con

du

ctiv

ity

,re

spec

tiv

ely

.

U1 I :::

TABL

E5-

10.

THER

MAL

AND

PHYS

ICAL

PROP

ERTI

ESOF

PITC

HFA

BRIC

PHEN

OLIC

Vir

gin

Mat

eria

lC

har

Nom

inal

Res

inR

ein-

The

rma1

Con

duct

i vit

yT

herm

a1C

ondu

ctiv

ity

Nom

inal

Res

inH

eat

of

forc

emen

tF

ail

Mat

eria

lD

ensi

tyM

ass

For

mat

ion

E1em

enta

1E

lem

enta

lT

empe

ratu

reS

pec

ific

x1

0'

(Btu

/ft-

sec-

OR

)S

pec

ific

x1

0'

(Btu

/ft-

sec-o

R)

Fra

ctio

nFo

rmu1

aFo

rmu1

aT

empe

ratu

reH

eat

Em

issi

vit

yH

eat

Em

issi

vit

y0°

90°

0°90

°(l

b/f

t')

(Btu

/1bm

)(P

hen

oli

c)(O

R)

(OR)

(Btu

llbm

-OR

)la

yup

layu

p(B

tull

bm-O

R)

layu

pla

yup

I-

Pit

chF

abri

c10

2.26

00

.11

9-3

79

.05

C 6H 6OC

-53

00.

120

1.3

02

.90

0.8

50

.21

01

.60

18

.75

0.8

5P

heno

lic

800

0.3

20

1.4

52.

94-

MX

G10

33F

1000

0.3

80

1.5

03

.24

0.4

30

1200

0.43

01

.50

3.43

-14

000

.44

03.

450

.47

0

2000

0.48

4

3000

0.4

93

17.2

5

4000

0.49

81

2.3

0

5000

0.50

01

.20

7.2

0----

a)T

hede

com

posi

tion

kin

etic

con

stan

tsfo

rp

hen

oli

cre

sin

are

tab

ula

ted

belo

w.

Rea

ctio

nPO

iP

riB i

'l>i

Ea/

Rr

i(l

bm

/ft'

)(l

bm

/ft'

)(s

ec')

(OR

)

11.

0226

a6.

4977

x1

0'

0.83

812

095.

02

101.

2374

90.3

949

2.09

904

xla

'2.

667

2337

2.a

1.0

3-

--

--

bl

The

foll

ow

ing

equ

atio

nis

sug

ges

ted

for

layu

pan

gle

so

ther

than

O~an

d9

0.

{(

k900

).

}k e

=ko

o1

+~

-1

S1

0e

whe

ree

isth

e1,

ayup

ang

lere

fere

nce

dto

atM

gen

tto

the

surf

ace.

clT

heco

nd

uct

ivit

yis

give

nby

k=

xkp

(T)

+(1

-x)

kc(T

)

whe

rex

isth

ev

irg

inm

ater

ial

mas

sfr

acti

on

.an

dk p

and

k car

eth

ev

irg

inm

ater

ial

and

char

con

du

ctiv

ity

.re

spec

tiv

ely

.

U1 I .j

:>N

TABL

E5-

11.

THER

MAL

AND

PHYS

ICAL

PROP

ERTI

ESOF

CANV

ASPH

ENOL

IC

Vir

gin

Mat

eria

lC

har

Nom

ina

1R

esin

Rei

n-T

herm

a1

Con

duct

ivit

yT

herm

a1

Con

duct

ivit

yN

om;n

a1

Res

;nH

eat

of

forc

emen

tFa

i1M

ater

ial

Den

sity

Mas

sF

orm

atio

nE

lem

enta

lEl

emen

ta1

Tem

pera

ture

Sp

ecif

icx

lD'

(Btu

/ft-

sec·

oR

)S

pec

ific

xl0

'(B

tu/f

t-se

CO

R)

For

mul

aT

empe

ratu

\"e

Emis

siv

ity

Em

issi

vit

yF

ract

ion

Form

ula

Hea

t0°

,90°

Hea

t0°

90°

(lb

/ft'

)(B

tul1

bm)

(Phe

noli

c)

(OR

)(O

R)

(Btu

/1bm

-OR

)la

yu

pla

yu

p(B

tu/l

bm-O

R)

layu

pla

yu

p

Can

vas

Phe

nol

ic8

8.2

88

0.7

10

-19

44

.88

C 6H 6OC 6H

lOO 5

-53

00

.36

00

.86

1.1

70

.85

0.2

10

2.5

02

.50

0.8

5.

800

0.4

40

0.9

0-

4K95

0210

000.

500

0.9

20

.43

0

1200

0.54

00

.93

-14

000

.47

0

2000

0.4

84

5.0

05

.00

3000

0.4

93

12

.50

12

.50

4000

0.4

98

19

.75

19

.75

5000

0.5

00

28

.50

28

.50

a)T

hed

eco

mp

osi

tio

nk

ineti

cco

nst

ants

for

ph

eno

lic

resi

nar

eta

bu

late

dbe

low

.

Rea

ctio

nPO

iP

riB

iW

iE

a;lR

ri

(lb

m/f

t')

(lb

m/f

t')

(sec'

)(O

R)

16

.62

20

5.92

85x

10

'1.

091

1009

6.0

28B

.906

02.

3929

5x

10

"1.

317

3560

2.0

0.5

38

1.0

48

51.2

062.

3755

8x

10

'3.

101

2822

5.0

b)T

hefo

llo

win

geq

uat

ion

issu

gg

este

dfo

rla

yu

pan

gle

so

ther

than

0°an

dgo

o

k e=

koo{

l+(~

~~O

-l)s

ine}

whe

ree

isth

ela

yup

ang

lere

fere

nce

dto

ata

ng

ent

toth

esu

rfac

e.

c)T

heco

nd

uct

ivit

yis

giv

enby

k=

xkp

(T)

+(l

-x

)kc(

T)

whe

rex

isth

ev

irg

inm

ater

ial

mas

sfr

acti

on

.an

dk p

and

k car

eth

ev

irg

inm

ater

ial

and

char

con

du

ctiv

ity

,re

specti

vely

.

SECTION 6

CONCLUSIONS

In summary, the following conclusions can be extracted from this study:

• With the exception of molding compounds and Kureha fabric, all carbon phenolics perform

equal to or better than MX4926 in the APG.

• With the exception of hybrid materials the performance of a particular generic class was

not especially dependent upon the material supplier.

• Higher mass losses in the 90° orientation are due to thicker char formations (higher con

ductivities).

• Kynol materials had satisfactory thermal performances in the APG, but they are not really

low cost materials. However, these materials may be considered as good alternate materials.

• Pitch carbon mat materials have a combination of good performance and low cost.

• There was a large variance in residual volatile measurements but no obvious correlation

between this and ablation performance was found. However, post-cured materials generally

performed better than as received materials.

• Data required for thermal performance predictions were determined for thermal conducti

vity (both 0° and 90° orientations), specific heat, density, pyrolysis kinetics, heat of

formation, and pyrolysis gas elemental composition. These data will subsequently be used

as inputs to the Aerotherm computer codes (ACE and CMA).

6-1

REFERENCES

1. Moyer, C. B. and Rindal, R. A.: "An Analyses of the Coupled Chemically Reacting Boundary Layerand Charring Ablator, Part II Finite Difference Solution for the In-Depth Response of CharringMaterials Considering Surface Chemical and Energy Balances," NASA CR-1061 (Aerotherm FinalReport 66-7, Part II), June 1968.

2. Schaefer, J. W. and Dahm, T. J.: "Studies of Nozzle Ablative Material Performance for LargeSolid Boosters," NASA CR-72080 (Aerotherm Report No. 66-2), December 15, 1966.

3. Baker, D. L., Wool, M. R., and Schaefer, J. W.: "A Dynamic Technique for Determining theThermal Conductivity of Charring Materials," Paper presented at the Eighth Conference on ThermalConductivity, October 7-11, 1968, Thermophysical Properties Research Center, West Lafayette,Indiana.

4. McCuen, P. A., Schaefer, J. W., Lundberg, R. E., and Kendall, R. M.: "A Study of SolidPropellant Rocket Motor Exposed Materials Behavior," Report No. AFRPL-TR-65-33 (Vidya ReportNo. 149), February 26, 1965.

5. Schaefer, J. W., et al.: "Studies of Ablative Material Performance for Solid Rocket NozzleApplication," NASA CR-72429 (Aerotherm Report No. 68-30), March 1, 1968.

R-l

APPENDIX A

RESIDUAL VOLATILE MEASUREMENTS

Coded samples of each screening test material were sent to Hexcel Corporation for a determin

ation of the residual volatile concentrations. These tests were performed in an attempt to resolve

the anomalous arc plasma jet performance of MX4926 in the Series tests. In these screening tests,

MX4926 exhibited severe delamination when convectively heated with the fabric plys parallel to the flow

direction. This delamination was of special concern since all other materials exhibited little or

no delamination problems. The residual measurement was one of two steps being taken to determine

the reasons for this delamination.

The residual tests were conducted by crushing appropriate size samples which were then des

iccated for 48 hours and weighed. These dried samples were heated at 325°F for 4 hours, removed

from the oven and desiccated for an additional 3 hours and weighed again. The percentage weight

loss was defined as the percent residual volatiles content. In some cases, two measurements were

made on the same material (but not necessarily the same physical block) to determine consistency.

Since the cure size may influence the magnitude of the residuals the approximate dimensions of the

as-received materials are shown along with the volatiles content in Table A-l. For cases where two

samples were measured the block sizes of each sample, if different, are also shown.

From Table A-l it can be seen that the measurement repeatability was very good when samples

were taken from the same size blocks. However, there is some dependence on block size as seen in

sample numbers 2, 5, 12, and 14. The Fiberite materials showed consistently higher volatile contents

for 2" diameter samples than for flat blocks (e.g., 4 x 4 x 1-1/2). The reverse is true for the

Hexcel material although only 1 material was tested redundantly.

The residuals content of the MX4926 was the lowest of all materials tested. This measured

value of 0.56 percent may be compared with a value of 1.1 percent as measured by Fiberite. This

difference is probably due to measurement techniques since there is no industry-wide accepted standard

for residual volatiles measured techniques. The significance of the reported measurements is that

all materials were measured under identical conditions and can therefore be ranked in a relative

A-l

TABLE A-1. SCREENING MATERIAL RESIDUAL VOLATILE MEASUREMENTS

Number Material Supplier Designation As Received %ResidualDimensions* Volatiles

1 Pitch Mat/Phenolic USP Fr~5782BG 5-1/2 x 5-1/2 x 3/8 2.05

2 Pitch Mat/Phenolic Fiberite MX4929 4 x 4 x 1-1/2 1.15/1.40

3 Pitch Mat/Phenolic Ferro ACX-C86PM 2-1/2 x 2-11/16 x 1-7/8 1. 38/1. 39

4 Hybrid Hexcel 4CSP08/4C1008 2-1/8 x 1-3/16 x 1-5/16 1.49/1.455 Hybrid Fiberite MX4928 20 x 1-3/4 1. 97/1.446 Hybrid USP FM5790 6 x 6 x 1-1/4 2.81

7 Kyno1/Phenolic Ferro ACX-CPH -4x4x3 1. 45/1. 47

8 Kyno1/Pheno1 i c USP XFM5795 6 x 6 x 1-1/4 5.41

9 Kureha/Phenolic Ferro ACXCB6K 2-1/2 x 2-11/16 x 1-7/16 4.08/4.0010 Molding Compound USP FM5782MC 20 x 1-3/4 1. 7611 Molding Compound Fiberite MXC313P 20 x 1-3/4 1.0812 Molding Compound Hexcel 4CSP08MC 30 x 1-1/2 1. 44/1. 69

2-3/8 x 1-3/8 x 1-3/8

13 Molding Compound Ferro ACX-CB6PMC 4 x 4 x 2 2.3314 Sil i ca/Pheno1i c Fiberite MX-260D 20 x 1-7/8 4.19/1.23

4 x 4 x 1-1/215 Sil ica/Pheno1 ic Ferro CA/2221/96 1-9/16 x 2-3/8 x 1-3/4 2.22

16 Sil ica/Pheno1 ic Fiberite MXSE-55 4x4x1-1/4 1.8317 Canvas/Phenolic Hexce1 4K9502 4 x 4 x 1 4.2618 Canvas/Phenolic Fiberite MXKF-418 4 x 4 x 1-1/4 4.1219 Canvas/Phenolic Fiberite MX4926 20 x 1-3/4 0.56*First 2 dimensions define plane of fabric or mat layup. Cylindrical samples have layup

perpendicular to axis.

A-2

sense. Since the residual's content of MX4926 was lower than the other materials, the delamination

problem cannot be attributed to a high volatile content. Since there is no rationale for relating

delaminations to low volatiles content, it is concluded that volatiles evolution during APG testing

did not cause the observed delaminations.

A-3

acurex corporation/aerotherm. division aerotherm … · carbon phenolic (e.g., fiberite mx 4926)....

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