PSI - Issue 64

Quentin Sourisseau et al. / Procedia Structural Integrity 64 (2024) 893–900 Quentin SOURISSEAU/ Structural Integrity Procedia 00 (2019) 000 – 000

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4a), and the energy release rate in function of the crack tip position can be plotted. Several methods exist for the determination of the energy release rate. We chose to use the CCM (Compliance Calibration Method) methodology for mode I, and the J-integral method developed in Rice (1968) and Leffler et al. (2007) for the mode II. An example of such a plot is given in Figure 4b. This allows to determine the critical energy release rate using the plateau value.

a) b) Fig. 3: Force/displacement curve (a) and selection of several strain profiles along the sample length (b) for a DCB test.

a) b) Fig. 4: Crack tip position determination (a) and critical energy release rate against crack tip position using the CCM method (b) obtained for a DCB test. For all tested specimens, the failure was mixed, occurring at GFRP (Glass Fiber Reinforced Polymer)/GFRP interface and GFRP/Steel interface. The obtained critical toughnesses are given in Table 1. It can be observed that, for the studied interface, the critical energy release rates are close between mode I and mode II, which is not what is classically encountered. The obtained toughnesses in case of mixed mode were determined following the methodology of ASTM D6671. It should be noted that the adequacy of those methodologies should be further investigated.

Table 1: Critical toughness (in kJ/m²) obtained for mode I and mode II for the studied equivalent interface Sample (Mode I) Mode I (CCM) Sample (Mode II) Mode II (J integral) Sample (Mixed Mode 55%) Mixed mode (55%)

Sample (Mixed Mode 75%)

Mixed mode (75%) (ASTM D6671)

(ASTM D6671)

DCB-1 DCB-2 DCB-3

1.78 1.95 1.48

ENF-1 ENF-2 ENF-3 ENF-4 ENF-5

1.11 1.26 1.86 1.65 1.42 1.46 20 %

MMB55-1 MMB55-2 MMB55-3

1.7 1.3 1.2

MMB75-1 MMB75-2 MMB75-3 MMB75-4

0.9 0.94 0.93 0.98

Average

1.74 14 %

1.4

0.94

Standard deviation/average

19 %

3.5 %