PSI - Issue 17

Andrey V. Babushkin et al. / Procedia Structural Integrity 17 (2019) 658–665 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

661

4

4. Research results

Uniaxial tensile tests were carried out on an Instron 5989 electromechanical system in accordance with the recommendations of ASTM D 3039 (ASTM International, 2017). The rolling grip speed was chosen to be 2 mm / min. The load was measured with a torque sensor with a maximum load of 600 kN. The measurement accuracy was 0.5% of the measured value in the 0.2-1% range of the sensor rated maximum load and 0.4% of the measured value in the 1-100% range of the sensor rated maximum load. To measure the longitudinal deformation of the samples, a non-contact video extensometer was used. For measurement of transverse deformations, an Epsilon 3575-250M-ST mounted extensometer was used with the maximum possible deviation from the measured value of 0.2%. According to the test results for each group of samples, stress-strain diagrams were constructed and basic mechanical characteristics were obtained, including mean values, standard deviations and coefficients of variation. According to the test results, the following characteristics of materials were determined: breaking load (kN); tensile strength (MPa); elastic modulus (GPa); Poisson's ratio; longitudinal deformation (%). Characteristics were determined according to deformation diagrams according to ASTM D 3039 recommendations. Uniaxial compression tests were carried out on an Instron 5982 electromechanical system in accordance with the recommendations of ASTM D 3410 (ASTM International, 2016). The speed of the rolling grip was chosen to be 1.5 mm / min. The load was measured with a load cell with a maximum load of 100 kN. The measurement accuracy was 0.5% of the measured value in the range of 0.2-1% of the rated maximum load of the sensor and 0.4% of the measured value in the range of 1-100% of the rated maximum load of the sensor. Deformations were determined using the Vic 3D three-dimensional digital optical system. Also, some samples were tested using the Vallen-Systeme GmbH AMSY-6 acoustic emission system and the FLIR SC7700M infrared thermal imaging system. According to the test results, load-displacement diagrams were constructed for each group of samples and mechanical characteristics were determined. As a result of the tests, the following characteristics were determined: maximum compressive load (kN), compressive strength (MPa), compressive modulus (GPa), classification of damage according to ASTM. Characteristics were determined by loading diagrams according to ASTM D 3410 recommendations. In-plane shear tests were performed on an Instron 5982 electromechanical system in accordance with the recommendations of ASTM D 5379 (ASTM International, 2012). The rolling grip speed was chosen to be 2 mm / min. A special device was used to carry out shear tests. The sample was inserted into the fixture and centered using the align tool. Shear deformations were determined using the Vic-3D three-dimensional digital optical system, and every third sample was tested using the Vallen-Systeme GmbH AMSY-6 acoustic emission system. For every type of test, ten samples of each typology of pattern were tested. From the tests, the ultimate shear strength Fu (MPa), the ultimate shear strain γa (%), shear modulus G (GPa), and the conventional shear strength F° (MPa) were determined. According to the test results for each group of samples, stress-strain diagrams and load displacement traverse diagrams were constructed, and the main mechanical characteristics were determined according to ASTM D 5379. The results of testing samples of carbon-reinforced plastics of all eight 3D preform weaving techniques (A-H series) for determining the basic characteristics of tensile, compression and shear are presented in Table 1.

Table 1. The results of determining the CFRP structures eight types basic characteristics.

3-D weaving

Series G

Series H

Series A Series B

Series C

Series D

Series E

Series F

Characteristic

1. Stretching

Max. load, kN

66,0 940

64,31

41,30

51,7 758

34

31,7 461

19,7 317

20,8 336

Strength, MPa

922,10

599

496

Elastic modulus, GPa Coefficient Poisson

61

68

45

55

35

40

38

38

0,07

0,06

0,27

0,04

0,20

0,43

0,18

0,19

2. Compression

Strength, MPa

428,71

473,82

132,90

237,12

111,24

155,63

248,14

203,00

Elastic modulus, GPa

61

63

42

57

41

49

48

48

3. Shear