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This report contains 14 pages. The shortened or partial reproduction or duplication of this report requires the approval of the Institute of Concrete Structures and Structural Engineering of the TU Kaiserslautern.

CIVIL ENGINEERING INSTITUTE OF CONCRETE STRUCTURES AN

STRUCTURAL ENGENEERING

Prof. Dr. – Ing. Matthias Pahn

Paul-Ehrlich-Straße Gebäude 14, Zimmer 570

67663 Kaiserslautern Telephone (0631) 205 – 3083

Telefax (0631) 205 – 3555 e-mail: [email protected]

Project 17059MLK/14511: Tensile tests on GFRP ø 32 mm according to ISO 10406

Client: RABDION LTD. 24 HaMa´as St Jerusalem, Israel

Contact: Stefan Harenberg M.Sc. [email protected]

www.massivbau-kl.de

Date: 09.02.2018

___________________________ ___________________________

Prof. Dr.-Ing. Matthias Pahn Stefan Harenberg M.Sc.

Project 17059MLK/14511 from 20.11.2017 of 14 Tensile tests on GFRP ø 32 mm according to ISO 10406

Contents

1. Introduction ..................................................................................................................... 3

2. Test program .................................................................................................................. 4

3. Test setup ....................................................................................................................... 5

4. Test specimen ................................................................................................................ 7

5. Evaluation of results ....................................................................................................... 8

6. Fracture state ............................................................................................................... 11

7. Summary ...................................................................................................................... 13

8. Bibliography .................................................................................................................. 14


1. Introduction

The company RABDION LTD. commissioned the Institute of Concrete Structures and Structural

Engineering of the Technical University Kaiserslautern to carry out tensile tests on bars of Glass Fiber

Reinforced Polymer (GFRP). Tensile tests are performed on the nominal diameter d = 32 mm.

During the tests, the force and the change in length are measured and documented to calculate the

force, young’s modulus, tensile strength and elongation.


2. Test program

The test program consists of 3 tensile tests and is shown in Table 1.

Table 1: Test program

Test program

Diameter Material Test type Basis Result Number of tests

Sample ID

32 mm GFRP Tensile

test

According to: ISO 10406

young modulus,

Force, tensile strength,

elongation.

3

RABDION _GFRP_32_1

RABDION _GFRP_32_2

RABDION _GFRP_32_3

The GFRP bars are glued in steel tubes. The test specimens are stored and tested under laboratory

conditions at approx. 22 ° C and 60% relative humidity.


3. Test setup

The test setup is according to ISO 10406-1 [1].

Figure 1: Test setup in according to ISO 10406-1 [1]

For the tensile test, the specimens are inserted centrally with clamping wedges in the tensile testing

machine. The force is introduced between clamping wedges and testing machine via spherical calotte

③. As a result, the specimens are freely rotary to the testing machine (see Figure 3).

The testing rate is 15 mm / min [1]. The force is measured by a load cell 1000 kN (MS 1.3.33) and the

length change of the rod with an extensometer ⑤ mounted in the middle of the bar (see Figure 2).

The extensometer (MS 1.7.1) has a clamping length of 50 mm.

① Load introduction frame

② Load introduction element

③ Clamping wedges+ spherical calotte

④ Test specimen

⑤ Extensometer

①

②

③

④

⑤

F

F


Figure 2: Extensometer on the centre of the test specimen

Figure 3: ① load introduction frame, ② load cell, ③ spherical calotte, ④clamping wedges,

⑤ load introduction pipe

②

③

④

①

⑤


4. Test specimen

Figure 4 shows the geometry of the test specimen. The bars are made out of GFRP which have

surface shaped in form of helical ribs. The bars have a nominal diameter ØN of 32 mm and have a

measured core diameter Øc of ≈ 31 mm (see Figure 4). The core diameter is the mean value of three

measurements along the length of the bars.

Figure 4: Geometry of the test specimen

A visual inspection reveals that the bars are straight and have no initial deflection. Figure 5a) and b)

shows on of the bars glued into the load introduction pipe and mounted in the testing machine.

a) b)

Figure 5 a),b): bar mounted in the testing machine

Øc ≈ 31mm

ØN = 32mm

1100 mm 1100 mm 1000 mm

3200 mm

Ø = 57 mm Ø = 57 mm Øc ≈ 31 mm


5. Test results

In according to ISO 10406 the young-modulus is calculated from the difference between the load level

at 20% and 50% of the maximum tensile strength. Because the maximum tensile strength wasn’t

known, the first bar was loaded up to 410 kN on the basis of existing results from other Tensile tests

(see Figure 6 – curve: R.GFRP_32_1-y.m.).

Figure 6: Cylinderforce-stroke behaviour

As the extensometer is a contacting measuring instrument, it must be removed before the specimen

breaks. To remove the extensometer, the bar was relieved to 2 kN. Thereafter the bar was loaded up

to fracture (see Figure 6 – curve: R.GFRP_32_1-fract.). Therefore, the length change is not measured

until failure. It has been shown that the load up to 400 kN is convenient for the test of the young-

modulus. Therefore the other bars were tested in the same way. The non-linear gradient of the young-

modulus test curves (y.m.) results from the slippage of the clamping wedges and the alignment of the

spherical calotte.

The stress is calculated from the force F and the core area A as follows:

𝜎 =𝐹

𝐴 [𝑀𝑃𝑎]

The elongation is calculated from the length change and the initial length of the extensometer (l=50

mm) as follows:

𝜀 =∆𝑙

𝑙∙ 100 [%]

R.GFRP_32_1-fract.

R.GFRP_32_1-y.m.

R.GFRP_32_2-fract.

R.GFRP_32_2-y.m.

R.GFRP_32_3-fract.

R.GFRP_32_3-y.m.

0

100

200

300

400

500

600

700

0 5 10 15 20 25 30 35 40 45 50 55

Cyl

ind

erfo

rce

[kN

]

Cylinderstroke [mm]


The young’s modulus is calculated as follows [1]:

𝐸 =∆𝜎

∆𝜀 [𝑀𝑃𝑎]

Unmeasured elongation is extrapolated up to break. The elongation at fracture 𝜀𝑢 is calculated as

follows [1]:

𝜀𝑢 =𝐹𝑓

𝐸 ∙ 𝐴 ∙ 100 [%]

For the evaluation of the results the tensile stress, elongation and young modulus are calculated from

the measured data and the stress-strain behaviour is shown in Figure 7. The young modulus is

calculated from the difference between the load level at 20% and 50% of the maximum tensile strength

[1] (see Figure 7 – curve: Calc. young-modulus). The dotted curves (extrapolated 𝜀𝑢) show the stress-

strain behaviour up to the linear extrapolated elongation at fracture.

Figure 7: Stress-strain behaviour

R.GFRP_32_1 Calc. young-modulus



R.GFRP_32_1 extrapolated εu



0

100

200

300

400

500

600

700

800

900

0 2 4 6 8 10 12 14 16 18 20

Ten

sile

str

engt

h [

Mp

a]

Elongation [‰]


Table 2 shows the results overview of the tensile tests:

Table 2: Results overview

1 Measured with slide gauge (see chapter 4) 2 linear extrapolated value with calculated young-modulus

Results overview

Sample ID Core

diameter 1

Maximum

force

Tensile

strength

Young

modulus

Elongation

at failure 2

[-] [mm] [kN] [MPa] [MPa] [%]

RABDION _GFRP_32_1 30,94 627,6 834,7 54874,4 1,52

RABDION _GFRP_32_2 30,71 591,7 798,9 55509,5 1,44

RABDION _GFRP_32_3 31,08 642,0 846,3 46836,6 1,81

Mean value 30,91 620,5 826,6 52406,8 1,59


6. Fracture state

The fracture of the bars occurred in all of the test specimens in the free length (see Figure 8). The

bonding between the glass fiber and the resin was fractured up to the load introduction (see Figure

9a, b).

Figure 8: Test specimen after test


a)

b)

Figure 9a), b): load introduction after test


7. Summary

The company RABDION LTD. commissioned the Institute of Concrete Structures and Structural

Engineering of the Technical University Kaiserslautern to carry out tensile tests on bars of Glass Fiber

Reinforced Polymer (GFRP). The bars are stressed in a tensile testing machine under centric strain

up to failure. The young modulus, tensile stress and elongation of the GFRP bars are determined from

the recorded data.

The rupture occurred for all bars within the free length.

Table 3: Mean values of the results from the tensile test

1 Measured with slide gauge (see chapter 4) 2 linear extrapolated value with calculated young-modulus

Mean value

Core diameter 1 Number of

tests

Maximum

force

Tensile

strength

Young

Modulus

Elongation

at Fracture 2

[mm] [Piece] [kN] [MPa] [MPa] [%]

30,91 3 620,5 826,6 52406,8 1,59


8. Bibliography

[1] ISO 10406-1: Fibre-reinforced Polymer (FRP) reinforcment of concrete – Test methods, 2008 [2] ASTM D 7205/D 7205M-06: Standard Test Method for Tensile Properties of Fiber Reinforced

Polymer Matrix Composite Bars, 2010

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