PSI - Issue 47

J.P.M. Lopes et al. / Procedia Structural Integrity 47 (2023) 48–55 Lopes et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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3. Results 3.1. CZM validation

This section describes a preliminary CZM validation procedure to assure the numerical results’ validity in the numerical study that follows (considering the 2015). A double- L T -joint is considered with identical adhesives and adherend, as described in section 2.2. Fig. 4 presents the validation geometry, with emphasis to the double- L part to produce a T -like shape, and also void region in the curvature region. Since the model conditions are equal to those described in section 2.3, including analysis type, meshes, element reference and boundary conditions, positive validation can be extrapolated to the proposed numerical geometry. The following dimensions were considered: l =25 mm, B =25 mm, L T =80 mm, a =3 mm, double- L part thickness ( t P2 )=1, 2, 3 and 4 mm, L A =60 mm, r =5 mm and t A =0.2 mm. Initially, joint fabrication involved adherend milling and bending to acquire the L -shape, in the case of these adherends. All adherends were then sandblasted and cleaned with acetone in the bonding faces. The assembled specimens were cured in a steel jig that assured the correct geometry. The specified t A was achieved by calibrated shims positioned at the adhesive ends. Pressure application was accomplished by manually pressing the bonding surfaces with grips (Campilho et al. 2011b). The specimens were cured over a week period and, before testing, the excess adhesive produced during joint assembly were trimmed by milling. The joints were tested in an electro mechanical testing machine (Shimadzu AG-X 100) at room temperature (RT) and velocity of 1 mm/min. Each t P2 led to the fabrication of five specimens, whose average was then compared to the numerical predictions for validation.

Fig. 4. Geometry of the double- L T -joints for validation purposes.

Visual inspection to all tested specimens showed that failures were cohesive in the adhesive layer, which gives an indication about the correct fabrication procedure. Fig. 5 compares the numerical P m predictions with the experimental data (average and respective standard deviation). Both experimental and numerical P m evolution denotes the major influence of t P2 . Actually, P m significantly increases with t P2 , namely for higher t P2 .

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Fig. 5. Validation results: experimental and CZM comparison as a function of t P2 .