PSI - Issue 28

Mor Mega et al. / Procedia Structural Integrity 28 (2020) 917–924 M. Mega and L. Banks-Sills / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 2. Load-displacement curves for NPC stage of the C-ELS tests with the NL, visual, and 5% o ff set or maximum initiation load P indicated.

delamination length. It was observed that G Ic is approximately 1% of G IIc . The total critical interface energy release rate G ic = G Ic + G IIc (8) is presented in the third, seventh and eleventh columns of Table 1 for the NL, visual, and 5% o ff set or maximum initiation loads, respectively. In the last two rows of that table, average values and the coe ffi cient of variation (CV) are given. The FEAs were conducted on two-dimensional models using quadratic, quadrilateral, plane strain elements of type CPE8. Each mesh contained a total of approximately 17,700 elements. Two steel plates were added to the model, acting as the clamp of the C-ELS apparatus. The top and bottom edges of the steel plates were constrained so that all nodes along the two edges have the same displacement in the x 1 - direction (see Fig. 1). Two spring elements were added to compensate for the apparatus compliance. Each one connects the top and bottom steel plates and their sti ff ness K = 50 N / mm was calibrated according to the compliance measured from each test. Surface-to-surface contact interaction was implemented along approximately half of the delamination line, far from the delamination tip, to prevent interpenetration. There was a small delamination face opening near the delamination tip. Also between the specimen edges and the steel plates contact interaction was used. Displacement control was applied in the models Table 1. Results for the energy release rates G ic calculated by means of BT and J -integral methods for all C-ELS NPC specimens, as well as average and CV values. specimen NL visual 5% \ max P G ic (BT) J J vs G ic (BT) P G ic (BT) J J vs G ic (BT) P G ic (BT) J J vs G ic (BT) (N) (N / m) (N / m) (%) (N) (N / m) (N / m) (%) (N) (N / m) (N / m) (%) CELS-2-2 139.6 750.2 605.6 23.9 164.6 1041.8 841.0 23.9 171.6 1133.3 914.8 23.9 CELS-2-3 156.9 917.2 743.0 23.4 189.4 1336.3 1082.4 23.4 191.7 1368.7 1108.7 23.4 CELS-2-4 160.3 923.6 750.9 23.0 176.5 1119.3 910.0 23.0 179.1 1152.5 937.0 23.0 CELS-2-5 141.4 734.8 567.8 29.4 159.5 935.6 723.0 29.4 163.9 988.0 763.5 29.4 CELS-2-6 140.2 718.6 582.8 23.3 160.3 939.2 761.7 23.3 169.9 1055.5 856.1 23.3 CELS-2-7 151.7 872.8 705.6 23.7 146.9 818.0 661.3 23.7 157.4 939.5 759.5 23.7 average 148.4 819.6 659.3 166.2 1031.7 829.9 172.3 1106.3 889.9 CV (%) 7.0 14.6 13.8 8.9 18.3 17.6 6.2 12.6 11.6