As a second part of this series, the present study also addresses the water resistance of joints obtained by friction welding. Here, the mode II fracture is in focus, that is, 4-points end-notched flexure specimens (4-ENF) were investigated with various moisture contents (MCs). The critical energy release rate was decreasing at higher MCs. The maximal shear strength of the joining material, as determined by torsion tests, was also affected by high MCs. The experimental data were implemented in a finite element model (FEM) based on the cohesive law to simulate the behavior of welded connection in 4-ENF tests. The FEM results describe well the experimental load-displacement curves.