Issue 56

H. Bai et alii, Frattura ed Integrità Strutturale, 56 (2021) 16-45; DOI: 10.3221/IGF-ESIS.56.02

Crack initiation stress of crack ①

Crack initiation stress of crack ②

Average value of crack initiation stress

Number

G1

0.61

0.71

0.66

G2

0.78

0.72

0.75

G3

0.82

0.94

0.88

G4

1.07

1.11

1.09

G5

1.38

1.34

1.36

Table 9: Crack initiation stress of ductile group (MPa).

Crack initiation stress of crack ①

Crack initiation stress of crack ②

Average value of crack initiation stress

Number

H1

0.63

0.55

0.59

H2

0.86

0.76

0.81

H3

0.93

0.97

0.95

H4

1.11

1.13

1.12

H5

1.19

1.15

1.17

Table 10: Crack initiation stress of brittle group (MPa).

1.4

1.6

crack ① crack ②

1.4

1.2

1.2

1.0

1.0

crack ① crack ②

0.8

0.8

0.6

0.6

Crack initiation stress (MPa)

Crack initiation stress (MPa)

0.4

0.4

1.0

1.5

2.0

2.5

3.0

3.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Content of epoxide resin and polyamide (%)

Rosin content (%)

Figure 16: The crack initiation stress of two cracks in specimens.

Analysis of peak strain ① Peak strain of ductile group

The peak strain of the specimen with different epoxide resin-polyamide content was obtained by processing the experiment data, as shown in Tab. 11. The relationship between the peak strain of the specimen and the content of epoxide resin- polyamide is shown in Fig. 17. It can be seen from the figure that the minimum peak strain of the specimen is 0.80% and the maximum peak strain is 1.55%. Therefore, it can be considered that the change of the content of epoxide resin-polyamide has a relatively striking influence on the peak strain of the specimen. At the same time, with the increase of epoxide resin-polyamide content, the

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