Issue 47

F. Moroni et alii, Frattura ed Integrità Strutturale, 47 (2019) 294-302; DOI: 10.3221/IGF-ESIS.47.22 296 (a) (b) Figure 1 : Nominal size of TRAZ-CI (a) and TRAZ-BJ (b) speciments Figure 2 : Experimental setup of a TRAZ-CI test. Fracture toughness testing The same specimen is used for both DCB and ENF tests and it is shown in Fig. 3. Each adherent is made of 19 aligned along the 0° fiber direction. Figure 3 : Nominal dimensions of DCB specimens. *W = 150 (DCB) or 180 mm (ENF). Dashed-dotted circles represent the ENF supports and load application points. Co-bonded joints present an insert of a sheet of non-stick material at one side to create the starter crack. However, since the crack tip radius depends on the thickness of the non-stick sheet, fatigue precracking under mode I loading is performed to extend the crack a few millimeters. Fracture tests are performed under displacement control at a displacement rate of 2.5 mm/min, with partial unloadings for the evaluation of the compliance and, in turn, of the crack length and of the value of G I , G II (strain energy release rate under mode I or mode II loading, respectively) as a function of crack length (R-curve). The value of G I , G II are evaluated at each unloading point by FEM (Finite Element Modelling). The simulations are performed using ABAQUS 6.13 software. Joints are modeled using 2D plane strain models; boundary condition and loads (F) are applied as shown in Fig. 4 a) and b). ** adhesive