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Table 2 Results of average initiation, rest state, and G m G i fracture toughness and crack propagation length for the DCB tests

From: Fracture toughness of adherends bonded with two-part acrylic-based adhesive: double cantilever beam tests under static loading

Specimens Fracture toughness (Jm−2) Initiation fracture toughness (Jm−2) Rest-state fracture toughness (Jm−2) Difference between maximum and initiation fracture toughness (Jm−2) Crack propagation length (mm)
G max  = G IC G i G r G m G i a m a i a r a m a r a i
Aluminum alloy 1071  (195.4) 826.4 (144.9) 843.3 (120.2) 244.3 (95.9) 7.1 (2.9) 3.7 (2.5) 10.7 (2.4)
GF/PP 1438 (271.6) 1185 (270.2) 1059 (179.1) 253 (181.2) 3.1 (2.3) 9.1 (4.5) 12.2 (4.2)
CF/EP 1652 (225.2) 1344 (203.5) 1308  (197.3) 307  (149.7) 4.0 (0.8) 7.5 (5.4) 11.5 (5.6)
  1. The relatively high standard deviation (SD) value for the crack propagation length of the GF/PP specimens was attributed to adherend failure involving weak bonding between the glass fibers and PP. Glass fibers present at various depths from the surface caused a variation in the crack propagation length (a m a i ) because a crack will stop propagating when it reaches such obstacles