Issue 48

F.A.L. Viana et alii, Frattura ed Integrità Strutturale, 48 (2019) 286-303; DOI: 10.3221/IGF-ESIS.48.29 290 two 0.05 mm spacers, to produce the total t A . The adhesive was poured on one of the adherends, the joints were assembled and pressure was applied up to the adherends contacting the spacers. The mould was closed for curing the adhesive during one week. After this procedure, the spacers were removed, the excess adhesive trimmed, and one of the adherends sides was painted with white paint to measure the crack length ( a ), and a numbered scale was attached to both adherends in the painted side to follow the crack during the test. To prevent possible crack-tip blunting effects, before measuring a 0 in each specimen the crack was manually propagated in opening mode by a length between 1 and 3 mm and only then a 0 was measured. For each joint L O , five joints were manufactured and tested, either for. In total, 60 SLJ and 60 DLJ were tested. In this work, identical h values were considered for the inner and outer adherends, opposed to using cross-section balanced adherends at both sides of the bond region, i.e., considering the inner with twice the h value of the outer adherends [22]. However, this method does not compromise the objectives of comparing different adhesive joints and evaluating the CZM capabilities to describe the joints’ behaviour. Fabrication for these joints was simpler, and a different technique, based on the use of spacers between the adherends, was used to assure t A . Actually, the desired t A value was achieved by supporting the top adherend of the joint (SLJ) or the two outer adherends (DLJ) with calibrated blocks in the mould during assembly to assure the correct positioning between adherends. After bonding, the joints were then left to cure in a steel mould to guarantee the lengthwise adherend alignment and value of L O . To guarantee the correct alignment in the testing machine, 3 mm thick and 25 mm length tabs were also bonded at the joint edges. The specimens were cured over one week at room temperature, and the excess adhesive removed by milling techniques. Figure 2 : Geometry and dimensions of the SLJ (a) and DLJ (b). All specimens were tested in an electro-mechanical testing machine Shimadzu AG-X 100 with a load cell of 100 kN and at a strain rate (either tensile or shear) of 0.08 s - 1. Fig. 3 shows the test setup for the DCB (a) and ENF specimens (b).The test setup for the SLJ and DLJ is depicted in Fig. 4. a) b) Figure 3 : Test setup for the DCB (a) and ENF specimens (b).