Issue 65

A. Joshi et alii, Frattura ed Integrità Strutturale, 65 (2023) 59-73; DOI: 10.3221/IGF-ESIS.65.05

The mode I Interlaminar fracture toughness values against the crack length of the composites made of Na 2 CO 3 modified matrix and Glass fiber and plain Glass epoxy composites are shown in Fig. 7b indicates that composites consisting of 2wt% Na 2 CO 3 modified matrix-Glass fiber composite exhibited higher toughness during crack initiation and composites made of 1wt% Na 2 CO 3 modified matrix-Glass fiber composite displayed higher toughness during crack propagation. The rise in the values of fracture toughness during crack propagation may be attributed to a considerable amount of fiber bridging [6] which can be seen in Fig. 8(a) to Fig. 8(d).

Figure 9: Mode I Interlaminar Fracture Toughness of Epoxy Matrix Modified with Na 2 CO 3 and Pristine Glass Fiber (a) G IC values (b) G IP values. Fig. 9 (a) and Fig. 9 (b) show the fracture toughness values during crack initiation (G IC ) and crack propagation (G IP ) respectively. The composites consisting of 2wt% Na 2 CO 3 in Glass fiber epoxy composites exhibited higher toughness during crack initiation and the composites consisting of 1wt% Na 2 CO 3 in Glass fiber epoxy composites exhibited higher toughness during crack propagation. Overall, it is observed that composites consisting of epoxy matrix modified with 2wt% Na 2 CO 3 in Glass fiber epoxy composites exhibited higher toughness during crack initiation but during crack propagation, the same concentration of Na 2 CO 3 exhibited very less fracture toughness. The Tab. 4 shows the details of number of specimens tested for mode I fracture toughness during crack initiation (G IC ) with standard deviation,average and co-efficient of variance.

Average value of Mode I fracture toughness

Standard deviation of Mode I fracture toughness

Co-efficient of variance of Mode I fracture toughness

No.of Specimens Tested

SL.No Laminate

G IC

G IP

G IC

G IP

G IC

G IC

1 2 3 4 5 6 7 8 9

6 6 6 6 6 6 6 6 6 6

15 43 39 25 36 42 24 24 35 39

34 35 46 41

1.5 3.5

3.5 3.5 4.2 3.8 3.5 3.5 3.5 4

10

10.29

GE

2.94 3.62 4.38 8.33 8.33 8.33 8.33 8.57 7.69

10

MWCNT/GE 1 MWCNT/GE 2 MWCNT/GE 3 Al 2 O 3 /GE 1 Al 2 O 3 /GE 2 Al 2 O 3 /GE 3 Na 2 CO 3 /GE 1 Na 2 CO 3 /GE 2 Na 2 CO 3 /GE 3

3 2 3 2 2 3 3

9.13 9.26 9.41 9.58 9.51 9.72 9.30

42.5 36.5 36.8

3.5

36 43

4

10 9.09 Table 4: Number of samples tested, Average, Standard deviation, Co-efficient of variance for Mode I fracture toughness during crack initiation (G IC ) and crack propagation (G IP ). 27.5 2.5

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