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Durability of Aircraft Structural Composites Processed by VaRTM

Masahiro Moriyama, Kenichi Yoshioka, Akihiko KitanoToray Industries, Inc.

2

Contents

1. Background2. Fatigue Tests

i. OHC : Open Hole Compressionii. CAI : Compression After Impact

3. Environmental Exposure Testsi. Temperature Exposureii. Moisture Exposureiii. Thermal Cycle Exposureiv. Hygrothermal Cycle Exposure

4. Modeling of Fatigue Damage Propagation5. Conclusion

3

CFRP Aircraft Structures

CFRP Ratio in Aircraft Structures

CFR

P W

eigh

t Rat

io in

Str

uctu

re [w

t%]

First Flight Year

1995 1970 1975 1980 1985 1990 2000

100

80

60

40

20

0 2005 2010

F14 F15

S76

Learfan 2000

Avtek 400

Voyager

V22

LHK Stership

F16 F18

AV8B

B757

B767 A310

X29

ATR42 A300

EAP Rafal

JAS39

ATF

Rafal D

A320

ATR72

A340 B777

Rotorcraft Business jets

Smallaircraft

Largeaircraft

A340-600

A380

B787

1. Background

4

CFRP Fabrication Process

Common applications:

Trucks, Boats, Building structures, etc.

Large and complex parts Low costLow energy consumption

Prepreg / autoclave process (conventional)

De-molding

Resin prepreg

Autoclave

CFRP

Bagging Cure Prepregging Lay-up CF

Filming

Bagging film

CF

Resin Bagging film

Pump CFRP De-molding Bagging Cure Lay-up

VaRTM (Vacuum-assisted Resin Transfer Molding)

Advantage of VaRTM Process

Disadvantage of VaRTM Process CFRP properties

1. Background

5

A-VaRTM

VaRTMLarge and complex parts, Low cost

Trucks, Boats, Building Structures, etc.

Fabrication technologies<Toray>

<Mitsubishi Heavy Industries>

Material technologies<Toray>

Advanced-VaRTM“A-VaRTM”

Large and complex parts, Low cost, Low energy consumption High performance

Aircraft primary structural elements

A-VaRTM Definition

Problem of A-VaRTM

Insufficient durability data compared with traditional materials

1. Background

6

Summary

・Fatigue tests (CAI, OHC)

・Environmental exposure tests (assumed for aircraft use)

1. Acquiring durability data of A-VaRTM

2. Modeling of fatigue damage propagation

・Damage detection of OHC fatigue specimen

・Life prediction of OHC fatigue

Objective:Long-term degradation model of A-VaRTM

1. Background

7

OHC Fatigue Test Results2. Fatigue Data

305

Hol

e D

iam

eter

:6.3

5

38.1

Unit:mmCompression-CompressionR = 10 f = 5Hz

Stacking Sequence:[45/0/-45/90] 2S

0

10

20

30

40

50

1 10 102 103 104 105 106

Cycles to Failure

Min

imum

Stre

ss [k

si]

T800H/3900-2 (G145)

CZ8433DP/TR-A37

σmin

σmax

8

CAI Fatigue Test Results2. Fatigue Data

0

10

20

30

40

50

1 10 102 103 104 105 106

Cycles to Failure

Min

imum

Stre

ss [k

si]

T800S/3900-2B

CZ8433DP/TR-A37

270in-lbs

720in-lbs

Compression-CompressionR = 10 f = 5Hz σmin

σmax

Stacking Sequence:[45/0/-45/90] 3S

152.

4

101.6

Unit:mm

9

1. Temperature Exposure

4. Hygrothermal Cycle Exposure

t

T

100°C

t

T

60°C / 85%RH

2. Thermal Cycle Exposure

3. Moisture Exposure

3. Environmental Resistance Data

3min t

T

RT

-54℃

100℃

10min 3min

10min

(125℃ for T800S/3900-2B)

-55°C

82°C

t

T

35°C 95%RH

24min 24min 72min

(Condition of T800S/3900-2B)

t

T

49ºC/95%RH 12h

within 24hr -54ºC 5min

36min (1cycle )

-54ºC

T

60min

71ºC 5min

Conditions of Environmental Exposure

Conditions of environmental exposure were based on durability study of T800S/3900-2B.

10

Composite Testing1. CAI

2. OHC

3. IPS

[45/0/-45/90]3sImpact enegy = 30.5J (270in-lb)Deflection rate = 1.27mm/min

[45/0/-45/90]2sDeflection rate = 1.27mm/min

[45/-45]2sDeflection rate = 1.27mm/min

Mechanical properties were measured before and after environmental exposure.


11

CZ8433DP/TR-A37

Test Matrix of Environment Exposure Tests 3. Environmental Resistance Data

0cycle400cycles

2000cycles

4. Hygrothermal Cycle Exposure[49℃/95%RH→-54℃→71℃]

0hr1000hrs3000hrs

3. Moisture Exposure[60℃/85%RH]

0cycle3000cycles

2. Thermal Cycle Exposure[-54℃→100℃]

0hr3000hrs

1. Temperature Exposure[100℃]

IPSOHCCAI

12

Temperature Exposure [ 100℃]

0

10

20

30

40

50

60

0 1000 2000 3000 4000Exposure period [hrs]

CA

I [ks

i]

T800S/3900-2B

CAI After Temperature Exposure

0

10

20

30

40

50

60


CA

I [ks

i]

CZ8433DP/TR-A37

Average of blank specimen


13

0

10

20

30

40

50


OH

C [k

si]

OHC After Temperature Exposure

T800S/3900-2B

10

20

30

40

50


OH

C [k

si]

CZ8433DP/TR-A37



14

0

5

10

15

20

25


In-p

lane

she

ar s

treng

th [k

si]

IPS Strength After Temperature Exposure

T800S/3900-2B

Exposure period [hrs]

0

5

10

15

20

25

0 1000 2000 3000 4000

In-p

lane

she

ar s

treng

th [k

si]

CZ8433DP/TR-A37



15

CAI After Thermal Cycle Exposure

0

10

20

30

40

50

60

0 1000 2000 3000 4000Exposure period [cycles]

CA

I [ks

i]

0

10

20

30

40

50

60


CA

I [ks

i]

T800S/3900-2B CZ8433DP/TR-A37


Thermal Cycle Exposure [-54℃→125 or 100℃]

16

OHC After Thermal Cycle Exposure

10

20

30

40

50


OH

C [k

si]

10

20

30

40

50


OH

C [k

si]

00

T800S/3900-2B CZ8433DP/TR-A37



17

IPS Strength After Thermal Cycle Exposure

Exposure period [cycles]

0

5

10

15

20

25

0 1000 2000 3000 4000

In-p

lane

she

ar s

treng

th [k

si]


0

5

10

15

20

25

1000 2000 3000 4000

In-p

lane

she

ar s

treng

th [k

si]

0

T800S/3900-2B CZ8433DP/TR-A37



18

Moisture Exposure [60℃/85%RH]

CAI After Moisture Exposure

0

10

20

30

40

50

60


CA

I [ks

i]

0

10

20

30

40

50

60


CA

I [ks

i]

T800S/3900-2B CZ8433DP/TR-A37


19

OHC After Moisture Exposure

10

20

30

40

50

0

OH

C [k

si]

01000 2000 3000 4000


T800S/3900-2B CZ8433DP/TR-A37

10

20

30

40

50

0

OH

C [k

si]

01000 2000 3000 4000




20

IPS Strength After Moisture Exposure


0

5

10

15

20

25

1000 2000 3000 4000

In-p

lane

she

ar s

treng

th [k

si]

0

T800S/3900-2B


0

5

10

15

20

25

1000 2000 3000 4000

In-p

lane

she

ar s

treng

th [k

si]

0

CZ8433DP/TR-A37



21

CAI After Hygrothermal Cycle Exposure

0

10

20

30

40

50

60

CA

I [ks

i]

0 500 1000 1500Exposure period [cycles]

T800S/3900-2B

0

10

20

30

40

50

60

0 500 2500Exposure period [cycles]

CA

I [ks

i]

1000 1500 2000

CZ8433DP/TR-A37


Hygrothermal Cycle Exposure [-55℃→35℃/95%RH→82℃ or 49℃/95%RH→-54℃→71℃]

22

OHC After Hygrothermal Cycle Exposure

10

20

30

40

50

0

OH

C [k

si]

0 1000 2500


10

20

30

40

50

0

OH

C [k

si]

0500 1000 1500


T800S/3900-2B

500 1500 2000

CZ8433DP/TR-A37



23

IPS Strength After Hygrothermal Cycle Exposure

0

5

10

15

20

25

In-p

lane

she

ar s

treng

th [k

si]


T800S/3900-2B

0

5

10

15

20

25

In-p

lane

she

ar s

treng

th [k

si]


20001500

CZ8433DP/TR-A37



24

CT Image of OHC Fatigue Specimen

Fatigue behavior is dominated by delamination from the microbacking.

0.5mm

0％ 50％ 65％

80％ 95％

0°

90°

0° 0° 0°

0° 0°

Microbackling

Delamination

Delamination growth

Tool side

Viewpoint

σmin＝0.775σ0（Fatigue life is about 71,000 cycles.)

4. Modeling

25

y = 2E-55x21.27

1.0E-11

1.0E-10

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05100 1000

∆GI[J/m2]

da/d

N[m

/cyc

le]

Life Prediction of OHC FatigueAnalytical model

σ0

5mm

x

Distribution of σy

y

Delamination

σ0

6mm

6.35mm

a0=2mm

5mm

a1=6mm

σy=1.5σ0

σy=1.5σ0

Cross-section

Two delaminations

(1)Overview

(2)Analytical model

Analytical solution for fatigue life

∫ ∆=

1

0)(

a

anf Gm

daN

Nf:Cycles to failurea0:Initial delamination lengtha1:Final delamination lengthΔG:Energy release ratem,n:Fitting parameter

Fitting parameters were determined from da/dN plot during DCB and ENF fatigue tests.

4. Modeling

26

Analytical Result

Analytical result is in good agreement with experimental result.

S-N Curve (OHC)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1 10 100 1000 10000 100000 1000000

Cycles to Failure

Nor

mal

ized

Stre

ss

Experimental Data

Analysis

4. Modeling

27

Conclusion

Fatigue TestsOHC and CAI fatigue behavior of A-VaRTM material is similar to that of aerospace grade prepreg.

Environmental Exposure TestsMechanical properties of A-VaRTM material exhibited little degradation after environmental exposure tests.This is similar to that of aerospace grade prepreg.

Modeling of Fatigue Damage PropagationOHC fatigue behavior of A-VaRTM material is dominated by delamination from the microbackling of 0 degree layer.By parameterizing energy release rate and delamination length, analytical result of OHC fatigue life was in good agreement withexperimental result.