Issue 48

C. E. Cruz Gonzalez et alii, Frattura ed Integrità Strutturale, 48 (2019) 530-544; DOI: 10.3221/IGF-ESIS.48.51 540 Figure 8: Visual inspection of : a) DC-80, b) Betamate 120 and c) MP55420 test specimens. Figure 9: SEM fractographs of fatigue fractured single-lap shear specimens with overlap length of 50 mm containing MP55420 adhesive at fillet zone: a) rough surface, b) apparent striations, and c) resolved fatigue striations. The fractographic analysis from the fractured surfaces at the spew fillet area near steel side of single-lap shear specimens under fatigue with 70 % of maximum load and overlap length of 50 mm (higher shear loads and displacements than that of 12.7 mm group) containing MP55420 adhesive (Fig. 9) exhibited rough surfaces with fatigue fracture appearance within the adhesive (Fig. 9a) that exhibited lower cohesive strength [25]. At major magnification, it can be observed apparent and discontinuous fatigue striations, (see Fig. 9b), which were confirmed with larger amplification finding several short resolved fatigue striations, as can be presented in Fig. 9c). This features fatigue behavior could be favored with the application of 70 % of maximum fatigue load that reduced the test time, indicating that the fatigue mechanism would be decreased. Moreover, the extended plastic strain behaviour with the biggest elongation and lowest tensile strength, i.e., the a) b) c)