NASA Technical Memorandum 102540 z ._

Ultrasonic and Radiographic Evaluation of

Advanced Aerospace Materials:

Ceramic Composites

Edward R. Generazio

Lewis Research Center

Cleveland, Ohio

Prepared for

Physics Department Seminars

sponsored by John Carroll University

University Heights, Ohio, April 11, 1990

(NASA-1M-IO?540) ULT_ARONI£ ANO

RADIUGRAI_HIC FVALUATION O_ ADVANCFD

AFROSPACE MATERIALS: CERAMIC CO_POSTTES

(NASA) 12 D CSCL I_D

NgO-Z1401

Unclas

63139 0277017

ULTRASONIC AND RADIOGRAPHIC EVALUATION OF ADVANCED AEROSPACE MATERIALS:

CERAMIC COMPOSITES

Edward R. Generazlo

Natlonal Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135

O

!

L_

ABSTRACT

Two conventional nondestructive evaluation technlques were used to evaluate advanced ceramic composite materlals. It has been shown that neither

ultrasonic C-scan nor radiographic imaging can individually provide sufflclent

data for an accurate nondestructive evaluation. Both ultrasonic C-scan and

conventional radlographIc Imaglng are required for preliminary evaluation of

these complex systems. The material variations that have been Identified by

these two techniques are porosity, delamlnatlons, bond quality between laminae,

fiber alignment, fiber registration, fiber parallelism, and processing density

flaws. The degree of bonding between fiber and matrix cannot be determined by

either of these methods. An alternative ultrasonic technique, angular power

spectrum scanning (APSS) is recommended for quantification of this InterfacIal

bond.

INTRODUCTION

Advanced hlgh-temperature, Iow-denslty composite materials are being

developed for use in the next generation of aerospace systems. The High Speed

Civil Transport (HSCT, flg. l), an aircraft for transporting 250 passengers, at

Mach 3.2 for 5000 n ml and the National Aerospace Plane (NASP, fig. 2) a transportation system that will take off, fly at Mach 25 directly Into orblt and

land llke a conventional aircraft, will requlre advanced composite materials

for both propulslon and structural components.

2S0 PASSENGERS

4 "nJRBINEENGINES

Figure 1. - High Speed Civil Transport (HSCT). "-
Figure 2. - National Aero-Space Plane (NASP).

ORIGINAL P/_GE 1_

OF POOR QUALITY

These composite materla]s conslst of particles, whiskers, or fibers

embedded in ceramic or metal matrices. The fibers may be parallel and lle in

one plane (fig. 3(a)), layered to form crossplys (fig. 3(b)), woven into a

three-dlmenslonal pattern (flg. 3(c)), or wound to form cylinders. The composite matrix material may be polymeric, metallic, intermetal]Ic, or ceramic. The

wlde range of composite materials under investigation for advanced aerospace

systems is shown In table I. One advantage to using composites listed In

table I is the Increased ratio of ultlmate strength-to-density (fig. 4) over

conventlona] engine materials, e.g., superalloys llke Inconel I00 (IN-IO0).

The rapid progress in producing metal matrix composites has allowed actual

test components to be manufactured. Here the NARIoy-Z main combustion chamber

(figs. 5 and 6) lining can be replaced by a metallic composite (fig. 7) that

has a superior rupture strength.

TABLE I

I. Polymer Matrix Composites (PMC)

2. Metal Matrix Composites (MMC)

3. Intermetalllc (FeA], NIA], MoSi 2) Matrix Composites (IMC)

4. Titanium Metal Matrix Composites (TiMMC)

5. Ceramic Matrix Composites (CMC)

The propulsion engine for the HSCT Is shown In figure 8. IMC's and

TIMMC's will be used from the inlet up to the turbines. The uncooled turbines

and ejector nozzle will be constructed of CMC's. The NASP propulsion system Is

a hydrogen-fueled supersonic combustion ramjet (SCRAMJET). Both the engine and

airframe will require advanced composite materials. Heavy use of ceramic composites is expected because their light weight, hlgh strength and thermal

shielding properties.

Research on monollthlc ceramics (ref. I) lead to the current developmental

research on advanced high-temperature ceramic composites (ref. 2). A variety

2
_ND

_",_L_" ..,. ,, "-MATRIX

(a) Monotape composite with fibers aligned along one direction,

(b) [0°/90 °] cross.ply, laminated composite.

r TURBINE

./_-- CERAMIC

_i_i_../" / OR

I METALLIC

/// FIBERS

(c) 3-D woven fabric composite.

Figure 3. - Advanced composites.

6x10s

J

J r- ADV.TITkNIIUM

/ , METALMATRIX

_.._._._,_nl

4 41-" i __ _- ,Dr. crrx_c

}

, a!

I

o I

O _ 1040 1,_0 2044 2_0

TE]MPERATIARE,*K

Figure 4.. Strenot_io-denslty for advanced composites.
GIMBAL.._ ,,-DOME/INJECTOR

BEARING-"_ / =_,-,.--OXIDIZER

LOW-PRESSURE .__ FUEL _:_ 'Z_ PREBURNER

HOT-GAS .t.,<_ _/

MANIFOLD-_" :"_ _ ,L.._

/ _._"J, _ HIGH-PRESSURE

.....J _ "_ OXIDIZER TURBOPUMP

_-MAIN COMBUSTIONCHAMBER

HIGH-PRESSURE .Ar_ k

FUEL TURBOPUMP_ _oLOxI_

CONTROLLER

NOZZLE

Figure 5. - Space Shuttle Main Engine (SSME).

Figure 6. - SSME powerhead component arrangement,

ORIGINAL PAGE IS

OF POOR QUALITY

4
i/

0HFC

CU

PROPERTIES CONSTRUCTION

COPPER/TUNGSTEN

COMPOSITE

POTENTIALLYI.BX STRONGER

THAN NARLOY-Z

[] THERMALCONDUCTIVITY

[] RUPTURESTRENGTHAT

TEMPERATURE

COPPER

MATRIX

\

\

_,.

TUNGSTEN

FIBER"_

#f

l

/

NARLOY

Z

CU/W

COMPOSITE

ENLARGED

SECTION _-"

Figure 7. - Test MMC composite thrust (combustion) chamber,

(INTERMETALUCMATRIXCOMPOSITE)

llll I I[11 IIIt 2 l I1

!! !l--- !1

LOW ASPECTRATIO UNCOOLEDTURBINES ADVANCED

SWEPTFAN EJECTORNOZZLE

MAGNETICBEARINGS 2-b'_'AGELOW EMMISSIONS

DUCTBURNER

LOWEMISSIONS

PRIMARYBURNER

Figure 8. - HSCT engine materials.

of processing techniques are belng |nvestlgated in an effort to produce hightemperature compos|tes with optimized thermal and mechanlca] properties.

Plasma spraying, reaction bonding, s]urry press|ng and sinterlng are typ|ca]

technlques used to produce high temperature ceramic composites. These processes often result In a composite that has a wide var|abillty in mlcrostructure

that usually affects thermal and mechanical properties.

Ultrasonic C-scans and x-ray radiography are two techniques used for nondestructlve evaluation (NDE) of mlcrostructural variations. These NDE methods

reveal macroscopic Internal features or flaws such as delamlnatlons, porosity

and cracks. These are important when considering the use of the tested materlal where strength and integrity must be assured. It Is challenge to the NDE

community to assist In the development of these advanced materials.
BACKGROUND

Ultrasonic imaging can be done by several techniques. The most common

technique Is that used by commercially available ultrasonic Immerslon C-scan

systems. An uItrasonlc wave of known amplitude Ao Is transmitted through a

sample as is shown in flgure 9. The final amplitude Af Is used to form an

image that Is a representation of the relative attenuation or energy lost by

the ultrasonlc wave as It traverses through the sample. The amount of energy

lost (hlgh loss corresponds to decreased image intensity) is an Indication of

the amount of porosity, degree of bondlng between fiber and matrix, and unlformity of the sample (ref. 3). Advanced ultrasonic techniques (e.g., angular

power spectrum scanning (APSS)) for composites are being developed (ref. 3)

that will make use of pattern recognition algorithms in order to characterize

variations In porosity, flber-matrlx bonding, and sample uniformity.

T/UW_ER

r SAMPLE

Ao AF J

Figure 9. - Immersion u4lnuionlc C-scan arrangenwmt.

IIECIEV'ER

Ultrasonic evaluatlon of composites may be approached from two directions.

The complete composlte can be Interrogated as a whole system. The resultant

ultrasonic signals are compllcated and dlfflcult to interpret. Since the

actual scattering mechanisms that shape these signals has remained unknown

their Interpretation Is subject to uncertainty. An alternatlve to thls approach

Is to expllcltly determine the Interaction of ultrasound wlth each Individual

component or phase of the composite. Thls information Is then used for formulatlng theories that explain the ultrasonic slgnals obtained from the full composite system. Recent results (ref. 3) Indlcate that thls latter approach has

been sucessful and can be used to determlne mlcrostructural uniformity, and

mechanical and thermal Integrity. The dominant ultrasonlc scattering mechanIsms for SIC and Si3N 4 are llsted In table II (ref. 3). The information in

table II Is used to help Interpret ultrasonic C-scan Images. As the ultrasonic

wave travels through the composite, energy Is scattered out of the main beam

at each pore and fiber boundary. The amount of scatterlng Is an Indication of

the number, presence, and character of each of these boundarles.

TABLE II*

I. Symmetric diffractive scattering at Indlvldual pores (Airy (ref. 4))

2. Symmetric diffractive scattering at fibers (Young (ref. 5))

3. Asymmetric refractive scattering at density gradients (Snell (ref. 6))

*Grain boundary scattering Is negligible.
NONDESTRUCTIVE EVALUATION

Three composite systems were investigated using conventional ultrasonlc

C-scan (lO MHz, through transmission) and radiographic techniques. The three

composite systems were SIC/SI3N4 wlth SCS-6(140-_m dlam SIC fiber), SIC

(NIcalon)/Calcium Alum|noslllcate (CAS), and SIC (Nlcalon)/SIC.

The radiographic and ultrasonic C-scan of SIC/SI3N4 (SCS-6fiber),

EO°/90°_, laminated composite NASPcooTfng pane7 is shown in figure ]0. The

x-ray image reveals mlsallgned or bowed fibers. The ultrasonic Image indicates

that there are regions (dark) between the laminae that did not bond (delamlnat_ons). The x-ray data indicates that the specimen Is uniform In density, however, the ultrasonic data Indicates that there are large variations In the

amount of ultrasonic scattering throughout the sample area. It Is believed

that these variations are due to bond variations between the laminae.

ORIGINAL PAGE IS

OF pOOR QUALITY

'_. MISALIGNED

FIBERS

X-RAY IMAGE

r DELAMINATION

LAMINATED

SiC/SI3N 4 (SCS-6 FIBER), (0-_/90_],

MONOLITHIC _ "',,,J,/

ULTRASONIC IMAGE

Figure 10, - X-ray and ultrasonic C-scan images of SiC/Si3N 4 (SCS-6 fiberl, [0°/90_], laminated composite NASP

cooling panel.

Identically produced SiC/SI3N 4 (SCS-6 fiber), [0°/90°], Iamfnated composites can yield very different nondestructive evaluation results. Figure II

shows the radiographlc and ultrasonic data for two similarly produced samples.

The x-ray data indlcate that these two speclmens have similar densities. In

contrast, the low intensity of the ultrasonic image for speclmen A Indlcates

that there Is relatively poor bonding between lamlnae. The highest intensity

In the ultrasonic Image for specimen B Is a region having a good bond between

laminae.

When comparing the radiographic and ultrasonic images for the SIC

(Nlcalon)/Calclum Alumlnoslllcate (CAS), [o°/go°], laminated composites

(fig. 12), it is observed that low ultrasonlc Intenslty (dark) corresponds to

low density (light regions) In the x-ray image. Therefore, these dark ultrasonic regions are areas having low densltles and not poor interlamlnar bonds.
ULTRASONIC X-RAY

(A) (A)

l__------J

WELL BONDED REGION --' (B) 1 cm

(B)

Figure 11. - X-ray and ultrasonic C-scan images of similarly produced SiCiSi3N 4 (SCS-6 Fiber). {0=/90:],

laminated composites.

ULTRASONIC X.RAY

ORIGINAL PAGE IS

OF POOR QUALITY

LOW DENSffY LOW DENSffY

Figure 12. - X-ray and ultrasonic C-s_n images of SiC(SCS-6)/Calcium Aluminosilicate (CAS), [05/90 °] composites.

The woven structure of SIC (Nicalon)/SiC, laminated composltes yield very

dlstorted ultrasonic Images (fig. 13). For examp]e, compare ftgures 12 and 13.

Processing features, hlgh-denslty circular regions, can be found In both the

ultrasonic and x-ray data. The ultrasonlc Image |ntenslty Is low where the

density Is high (dark In the radlograph). The cross hatch pattern In the

radlograph reveals the degree of reglstration between lamina. Reglstration

effects can result In an erroneous determlnatlon of porosity varlatlons. Thls

occurs when nearly Identlcal p11es, wlth unlform fiber spacing, are lald up so

that the fibers are slightly off axls. Thls slight mlsalignment of f|bers produces a Molre (ref. 7) pattern (flg. 14) In the x-ray Image that may be mlslnterpreted as porosity variations. The large =number of fibers In ceramlc

composites results In an overlap, of Moire patterns. These overlapping pat.

terns are not as clearly visable as that shown In flgure 14. As of thls wrlting Moire patterns have not been expllcltly observed for ceramic composltes.

However, researchers should be aware of thelr effect on determ|natlon of

denslty.

The NDE of these systems indicates that for lamlnated composite structures

both radiography and ultrasonic C-scan evaluatlon are required. The x-ray

evaluation can be used to determine porosity varlatlons, fiber allgnment and

reglstration between layups. Ultrasonic evaluation can be used for determlnlng

delamlnations, bond variatlons between laminae and poroslty varlatlons.

8
X RAY IMAGE j_- HIGH DENSITY RE_

lcm

ULTRASONIC IMAGE

__ /-4.FlGH DENSITY REGIOM

Figure 13, - X-ray and ultrasonic C-scan images of woven, SiC(Nicalon)/

SiC laminated composite,

MOIRI_

/'_'-" VERTICAL / DARK

.,.-"_ / ,/ BANDS

"- W/Cu (200 pm diam, W RBER)

X-RAY IMAGE

Figure 14. - X-ray image of W/Cu composite showing Moir_ pattern.

ORIGINAL PAGE IS

OF POOR QUALITY'

In the above evaluatlons, the degree of bonding between the fiber and the

matrix cannot be separated from effects due to porosity and variations In the

number of fibers per unit volume. Further nondestructive analysis using the

APSS technique wlll be required to obtain this Information.

SUMMARY

Two conventional nondestructive evaluatlon techniques were used to evaluate advanced ceramic composite materials. It has been shown that neither

ultrasonic C-scan nor radiographic imaging can individually provide sufflclent

data for an accurate nondestructive evaluation. Both ultrasonic C-scan and

conventlonal radiographic Imaging are required for preliminary evaluatlon of

these complex systems. The material variations that have been identified by

these two techniques are porosity, delamlnatlons, bond quality between lamlna,

fiber alignment, fiber registration, fiber parallellsm, and processing density

flaws. The degree of bonding between fiber and matrix cannot be determined by

either of these methods. An alternatlve ultrasonic technique, angular power

spectrum scanning Is recommended for quantification of thls Interfacial bond.

REFERENCES

I. Structural Ceramics. NASA CP-2427, 1986.

2. HITEMP Review 1989: Advanced Hlgh Temperature Engine Materials Technology

Program. NASA CP-I0039, 1989.

3. Generazlo, E.R.: Theory and Experimental Technique for Nondestructive

Evaluation of Ceramic Composites. NASA TM-I02561, 19go.
4. Chou, C.H.; Khur1-Yakub, B.T.; and K1no, G.S.: Transmission Imaging:

Forward Scattering and Scatter Reconstructing. Acoustical Imaglnq,

Vol. 9, Visualization and Characterization, K.Y. Wang, ed., Plenum Press,

1980, pp. 357-377.

5. Ha111day, D.; and Resnlck, R.: Fundamentals of Physics. N11ey & Sons,

1970, Chapter 37.

6. Cooper, H.F., Jr.: Reflectlon and Transmission of Obllque Plane Naves at

a Plane Interface between V1scoelastlc Media. J. Acoust. Soc. Am.,

vo1. 42, no. 5, 1967, pp. I064-I069.

7. B1berman, L.M.: Perceptlon of Displayed Infor_atlon. Plenum Press, NY,

1973, Chapter 7.

10
- Report Documentation Page Nalional Aeronauhcs and

Space Admmislrabon

1. Report No, 2. Government Accession No,

NASA TM- 102540

4, Title and Subtitle

Ultrasonic and Radiographic Evaluation of Advanced Aerospace Materials:

Ceramic Composites

7. Author(s)

Edward R. Generazio

Performing Organization Name and Address

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

g,

Sponsoring Agency Name and Address

National Aeronautics and Space Administration

Washington, D.C. 20546-0001

!12.

3. Recipient's Catalog No.

5. Report Date

6. Performing Organization Code

8. Performing Organization Report No.

E-5403

10. Work Unit No.

510-01-1A

11. Contract or Grant No.

13. Type of Report and Period Covered

Technical Memorandum

14. Sponsoring Agency Code

15. Supplementary Notes

Prepared for the Physics Department Seminars sponsored by John Carroll University. University Heights. Ohio,

April 11. 1990.

16 Abstract

Two convcntipnaJ nondestructive evaluation techniques were used to evaluate advanced ceramic composite

• _'" % .......... ' V' " materials. It _n shown that norther ultrasomc C-scan nor ra&ographlc mlagmg can mdwtdually pro idc

sufficient data for an accurate nondestructive evaluation. Both ultrasonic C-scan and conventional radiographic

imaging are required for preliminary evaluation of thcse complex systems. The material variations that l_a_ccn

identified by these two techniques are porosity, delaminations, bond quality between laminae, fiber alignment.

fiber rcgistration, fiber parallelism, and processing density rlaws. The degree of bonding between fiber and

matrix cannot bc dctermined by either of these methods. An alternative ultrasonic technique, angular power

spectrum scanning (APSS) is recommended for quantification of this interfacial bond.

17. Key Words (Suggested by Author(s))

Composites; Nondestructive evaluation; Nondestructive

testing; NDT; NDE; Radiography; Ultrasonics

18. Distribution Statement

Unclassified- Unlimited

Subject Category 38

19, Security Classif. (of this report) 20. Security Classif. (of this page) 21. No, of pages

Unclassified Unclassified 12

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