PSI - Issue 41

A.R.F. Soares et al. / Procedia Structural Integrity 41 (2022) 48–59 Soares et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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The P -  curves were constructed with the values of P and  continuously registered during the tests. Table 2 presents the P -  curves referring to each test configuration.

Table 2. P -  curves for each configuration.

P- δ curves

1000 1500 2000 2500 3000

0 1000 2000 3000 4000 5000 6000

DCB_01 DCB_02

P2_01 P2_02

P [N]

P [N]

0 500

0

0.2 0.4 0.6 0.8

1

1.2

0

0.5

1

1.5

 [mm]

 [mm]

DCB_01/02

P2_01/02

10000 12000

1000 1500 2000 2500 3000 3500

ENF_01 ENF_02

P3_01 P3_02

0 2000 4000 6000 8000

P [N]

P [N]

0 500

0

5

10

15

0

0.5

1

1.5

2

2.5

 [mm]

 [mm]

P3_01/02

ENF_01/02

By the analysis of the P -  curves presented in Table 2, it is possible to verify that in the DCB_01 and DCB_02 configurations, the curves present several peaks followed by zones of unstable propagation, which represent regions of abrupt crack growth in the adhesive layer. The peak values are similar, except for the maximum peak values. Regarding the configurations P2_01, P2_02, P3_01 and P3_02, the curves are practically overlapped, and a higher maximum P is observed when compared with the DCB_01 and DCB_02 curves. On the other hand, for the configurations ENF_01 and ENF_02, the curves are linear up to the maximum P , which is in accordance with the brittle nature of the Araldite ® AV 138/HV 998. In this case, there is a notable mismatch between the two curves, which can be justified by an experimental cause, which occurred in specimen ENF_01, such as poor manufacturing. The almost overlapping of the curves confirms the repeatability of the tests, mainly in the configurations P2_01, P2_02, P3_01 and P3_02. 5. Conclusions This work aimed to design and validate an MMB equipment for mixed-mode testing of structural adhesives, covering the range between pure-modes I and II. The available solutions were carefully analysed and the proposed solution is an evolution of the work of Chaves (2013). The final design is initially presented, which is then described including the working principle, designed by FEM, fabricated, and validated. FEM validation consisted of applying the design load and emulating testing conditions in a static analysis, showing an SF>1. Details were given on the