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Tensile Testing of GEV307 at room Temperature

Investigation of blade material behaviour under external (extreme) conditions.

Work Package 9

OB_TG3_R027, rev. 002

10345

Final version Confidential

OPTIMAT BLADES

TG 3

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Issue/revision date pages Summary of changes Rev 000 200-01-29 18

Rev 001 2006-02-10 19

Added theoretical values

Rev 002 2006-03-17 22 Added analyses of failure modes

Rev 003 2006-03-28 22 New figures 11 and 12

Tensile testing of GEV307 at room temperature

Povl Brøndsted

Risø National Laboratory Roskilde Denmark

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Optimat report, TG3_R027, rev. 003 4

Author: Povl Brøndsted Title: Tensile testing of GEV307 in 1- and 2 direction

@ room temperature Department: Risø

Optimat report, TG3_R027, rev. 002

Contract no.:

Groups own reg. no.: (Føniks PSP-element)

Sponsorship:

Cover:

Pages: Tables: References:

Abstract (max. 2000 char.):

Risø National Laboratory Information Service

Department P.O.Box 49 DK-4000 Roskilde Denmark Telephone +45 46774004 bibl@risoe.dkFax +45 46774013

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Preface This report describes the tensile testing at room temperature of the OPTIMAT alternative material. The testing is a part of the deliverables in WP9 in TG3: “Investigation of blade material behaviour under external (extreme) conditions. Extreme conditions for alternative materials”

Based on the findings in phase 1, primarily from WP 8, a test plan has been prepared to establish a deeper understanding of the effects of the most detrimental environmental effects. These have been found to be elevated temperatures. A supplementary number of additional tests on the reference material and an investigation of the behaviour of an alternative material (glass fibres in an alternative resin is suggested) under the selected conditions are carried out.

The static tensile test are carried out according to the ISO 527 recommendation with the exception that the loading history are selected in loading-unloading sequences in order to be able to follow the damage growth during the tests.

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1 Test Programme.

The full test programme is shown in Figure 1 where the tests described in this report is highlighted

Test matrix for WP9Environmental conditions No of specimens to be tested

LaboratoryTotal static Fatigue

Test method T T T I C C T-T T-C C-C

LaminateMD 0

MD 90

MD 30

MD 90

MD 0

MD 90

MD 0

MD 0

MD 0

RT 5 5 5 5 10 5 35 10 10 10Riso 5 5 5 5 10 5 35 10VTT 0 10

WMC 0 10T 60 C 5 5 5 5 10 5 35 10 10 10

Riso 5 10 5 20 10VTT 5 5 5 15 10

WMC 0 10

Figure 1. Test plan for WP 9. Current tests are highlighted.

All static tests are planed to be carried out according to the international standard ISO 527/4 with the exception that the loading history includes loading-unloading sequences in order to follow damage evolution.

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2 Material and Test Specimens. The material tested is a Glass-Epoxy Multi Directional 5 x Biaxial 806 & 4 x Combi 1250 laminate vacuum injected with epoxy system E6/H6. The laminate is manufactured by LM Glasfiber A/S, material specification number GEV 307. The test specimens for the tensile tests are OPTIMAT type I0100 (1 direction) and I0190 (2 direction). They are procured by the manufacturer and cut out according to ISO 527-4, type 3 with end tabs. Test specimen geometry is shown in Figure 2.

In Table 1 and Figure 3 the theoretical values for the MD laminate are shown. Calculations are performed using the software programme CompositePro with a E-Glass-Expoxy laminate material.

Figure 2. Tensile test specimen.

Table 1. Laminate for theoretical calculation, Vol % Fibres = 54%

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Laminate Moduli

MPa

05000

1000015000200002500030000

Ex Ey GxyExb Eyb Gxyb

Figure 3. Theoretical Laminate Moduli

Table 2. Theoretical Values

LAMINATE PROPERTIES Extentional Properties: Ex (Pa)= 2.885E+10 Ey (Pa)= 1.549E+10 Gxy (Pa)= 8.151E+09 NUxy = 4.261E-01 NUyx = 2.288E-01 Flexural Properties:

Exb (Pa)= 2.580E+10 Eyb (Pa)= 1.560E+10 Gxyb (Pa)= 8.992E+09

NUxyb = -4.562E-01 NUyxb = -2.759E-01 Thermal Expansion Coefficients (CTE Units = m/m/C, CTEk Units = 1/m/C) CTEx = 7.914E-06 CTEy = 2.024E-05 CTExy = 3.708E-11 CTExk = -9.637E-08 CTEyk = -2.121E-07 CTExyk = -9.170E-06 Moisture Expansion Coefficients (CME Units = m/m/%, CMEk Units = 1/m/%) CMEx = 1.878E-04 CMEy = 1.060E-03 CMExy = 3.358E-09

CMExk = -7.697E-06 CMEyk = -1.812E-05 CMExyk = -6.523E-04

Physical Properties: Density (gm/m3)= 1.987E+06

Thickness (m)= 6.400E-02

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Test Procedure 2.1 Tensile testing in 1 direction.

The tests were carried out using an Instron 8533 hydraulic test machine with mechanical grips. The load is measured using a certified ±250 kN dynamic Instron load cell, UK 084. Longitudinal strain is measured using a strain gauge extensometer, Instron type 2620-600, #1747, ±1mm, 25 mm gauge length. Transverse strain is measured using a strain gauge extensometer, Instron type 2620-600, #1747, ±1mm, 22.5 mm gauge length. The testing is controlled in position control and run at 2 mm/min. The loading-unloading test sequences are controlled by Instron Wavemaker programme in a block sequence history shown in Figure 4.

Loading Sequences Tensile tests in 1 direction

-8

-6

-4

-2

0

2

4

6

8

0 200 400 600 800 1000 1200 1400

Time (sec)

Dis

plac

emen

t (m

m)

0

50

100

150

200

250

300

Load

(kN

)

Figure 4. Loading-unloading sequences for tensile test in 1-direction.

The test is controlled in the way that the position ramp is reversed when a

preset load value is reached. The reason for not choosing a preset strain value as target value is that the extensometers can jump when cracking occurs.

The test data are sampled in files with a sampling rate of 5 Hz. At a load level below failure load (≈ 60 kN) in the last sequence the

extensometers were removed from the specimen in order to protect them from damage at the final fracture.

A typical stress strain curve is shown in Figure 5.

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Tensile test GEV307-I0100-11

-100.0

0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

-2 -1 0 1 2 3 4

Strain (%)

Stre

ss (M

Pa)

Series1

Figure 5. Stress strain curve for a 1-direction tensile test.

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2.2 Tensile testing in 2 direction. The tests were carried out using an Instron 8842 hydraulic test machine

with Hydraulic grips. The load is measured using a certified ±100 kN dynamic Instron load cell, UK 054. Longitudinal strain is measured using a strain gauge extensometer, Instron type 2620-600, #1747, ±1mm, 25 mm gauge length. Transverse strain is measured using a strain gauge extensometer, Instron type 2620-600, #1747, ±1mm, 22.5 mm gauge length. The testing is controlled in position control and run at 2 mm/min. The loading-unloading test sequences are controlled by Instron Wavemaker programme in a block sequence history shown in Figure 6.

Loading Sequences Tensile tests in 2 direction

-8

-6

-4

-2

0

2

4

6

8

10

0 200 400 600 800 1000 1200

Time (sec)

Dis

plac

emen

t (m

m)

0

10

20

30

40

50

60

70

80

90

Load

(kN

)Load Profile

Displacement Profile

Figure 6. Loading-unloading sequences for tensile test in 2-direction.

The test is controlled in the way that the position ramp is reversed when a

preset load value is reached. The reason for not choosing a preset strain value as target value is that the extensometers can jump when cracking occurs.

The test data are sampled in files with a sampling rate of 5 Hz. The extensometers remain mounted on the test specimens until failure A typical stress strain curve is shown in Figure 7.

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Tensile test GEV307-I0190-03

-20.0

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

160.0

0 0.5 1 1.5 2 2.5 3

Strain (%)

Stre

ss (M

Pa)

Series1

Figure 7. Stress strain curve for a 2-direction tensile test.

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3 Data Handling. The following properties are extracted from the test data:

Stiffness, Young’s Modulus:

According to the ISO 527 the tensile modulus are defined as the slope of the stress strain curve in uniaxial tension between 0.05% and 0.25% strain. In order to measure a well defined modulus, it must be assured that the strain limits between which the slope is determined are correct. Hence, it is required, that the intercept point for the elastic line must be origin (0,0) in the stress-strain diagram. See Figure 8.

Poisson’s ratio

Poisson’s ration is defined as the ratio between transverse strain and longitudinal strain. It is calculated as the slope of the (T. strain – L. strain) line in the same range as the range wherein the Stiffness is calculated. See Figure 8.

Secant modulus:

This is defined as the slope of the unloading-loading loop parameters and calculated as a linear regression of all data in a loop. See Figure 9

Loop stiffness and Loop Poisson ratio

Loop stiffness and strain ration in the unloading-loading loop. Slope of stress-strain and L-strain-T-strain curve between 0.05% - 0.25% strain from minimum strain in the loop.

Damping

Defined as the area of the normalized loading-unloading hysteresis loop, Figure 10. Normalization values are mean and amplitude values. I.e.

Normalised value = (Value-(max+min))/(max-min)

Maximum-minimum strain in the unloading-loading loop

Maximum and minimum strains in the unloading-loading loop are found from the data.

All properties are automatically extracted from the data files in an Excel spreadsheet.

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Initial Stiffness and Poisson Ratio.

y = 269.42x - 9E-14

-20

0

20

40

60

80

100

-0.1 0 0.1 0.2 0.3 0.4 0.5

Longitudinal Strain (%)

Stre

ss (M

Pa)

-0.2

0

0.2

0.4

0.6

0.8

1

Tran

sver

se S

trai

n (%

)

Loading unloading sequences

Array between 0.05% and 25% for definition of Modulus

Elastic line through (0,0) Line for calculating Poisson's

ratio

Figure 8. Diagram illustrating the calculation of stiffness and Poisson's ratio.

Unloading-Loading loop

-100

0

100

200

300

400

500

600

700

0 0.5 1 1.5 2 2.5 3

Strain (%)

Stre

ss (M

Pa)

Loop Stiffness

Secant modulus

Figure 9. Unloading-loading loop

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Normalised Unloading-Loading loop

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

-1.50 -1.00 -0.50 0.00 0.50 1.00 1.50

Strain (%)

Stre

ss (M

Pa)

Damping = Area of normalised hysteresis loop

Figure 10. Diagram showing a normalized unloading-loading loop.

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4 Test results. The results from the tensile tests in the 1 direction are shown in Table 3, and the damage parameters from the loop analyses are shown in Figure 11.

Results from tensile tests in the 2 direction is shown in Table 4 and Figure 12. Tensile strength and Strain to failure in Tests GEV307-I0190-01 and GEV307-I0190-02 are non-valid because of failure in the grips. Se section 5.

Table 3. Results tensile test in 1-direction

Results Table GEV307-I0100

Specimen # Width (mm)

Thickness (mm)

Young's Modulus (MPa)

Poissons Ratio

Tensile Strength (MPa)

Strain to failure (%)

GEV307-I0100-07 6.52 25.38 27.39 0.39 655 3.04GEV307-I0100-08 6.53 25.45 27.44 0.43 616 2.85GEV307-I0100-09 6.51 25.62 26.67 0.39 629 3.10GEV307-I0100-10 6.50 25.59 29.16 0.42 596 2.78GEV307-I0100-11 6.49 25.55 26.94 0.40 580 2.97Average 27.52 0.41 615 2.95Stdev 0.97 0.02 29 0.13Stdev (%) 3.5 5.0 4.7 4.5

Table 4. Results tensile test in 2-directio. Marked cells indicate non-valid results

Results Table GEV307-I0190

Specimen #Width (mm)

Thickness (mm)

Young's Modulus (MPa)

Poissons Ratio

Tensile Strength (MPa)

Strain to failure (%)

GEV307-I0190-01 6.69 25.51 13.93 0.22 118 1.72GEV307-I0190-02 6.87 25.40 13.85 0.20 138 2.42GEV307-I0190-03 6.82 25.53 13.99 0.16 139 2.47GEV307-I0190-04 6.76 25.54 14.12 0.18 140 2.44GEV307-I0190-05 6.75 25.52 14.24 0.18 140 2.46Average 14.02 0.19 140 2.46Stdev 0.16 0.02 1 0.02Stdev (%) 1.1 13.1 0.6 0.8

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Tensile tests - 1 direction GEV307 - Damage in Loading-unloading

20

21

22

23

24

25

26

27

28

29

30

0.0 0.5 1.0 1.5 2.0 2.5 3.0Strain (%)

Stif

fnes

s (In

itial

and

Sec

ant)

(GP

a)

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

Inte

rcep

t stra

in (%

), D

ampi

ng,

Pois

son'

s ra

tion

StiffnessSecant ModulusInterceptPoissons ratioDamping

Figure 11. Damage properties from tensile tests in 1-direction.

Tensile tests - 2 direction GEV307 - Damage in Loading-unloading

0

2

4

6

8

10

12

14

16

18

20

0.0 0.5 1.0 1.5 2.0 2.5 3.0Strain (%)

Stif

fnes

s (In

itial

and

Sec

ant)

(GP

a)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Inte

rcep

t stra

in (%

), D

ampi

ng,

Pois

son'

s ra

tion

StiffnessSecant ModulusInterceptPoissons ratioDamping

Figure 12. Damage properties from tensile tests in 2-direction.

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5 Failure modes. Photographs of the failure modes of the specimens tested are shown in Figure 13 and Figure 14 (1-direction tests, and Figure 15 and Figure 16 (2 direction tests).

The failures in 1 direction can be characterized as overall splitting in the gauge area. The failures are apparently not influenced by the gripping and tabs areas.

The failures in the 2-direction are localized. For specimens 1 and 2 the failure is directly localized in the grip, whereas specimens 3, 4, and 5 fails localized close to the tabs and grips. These failures could be affected by bending. Based on the failure observations, the results from specimen 1 and 2 must be regarded as non-valid.

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Figure 13. Failure modes of GEV307-I0100 test specimens from the edge

Figure 14. Failure modes of GEV307-I0100 test specimens from the front

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Figure 15. Failure modes of specimens GEV-I0190 seen from the edge

Figure 16. Failure modes of specimens GEV-I0190 seen from the front

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Mission

To promote an innovative and environmentally sustainable technological development within the areas of energy, industrial technology and bioproduction through research, innovation and advisory services.

Vision

Risø’s research shall extend the boundaries for the understanding of nature’s processes and interactions right down to the molecular nanoscale.

The results obtained shall set new trends for the development of sustainable technologies within the fields of energy, industrial technology and biotechnology.

The efforts made shall benefit Danish society and lead to the development of new multi-billion industries.

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