PSI - Issue 54

D.F.T. Carvalho et al. / Procedia Structural Integrity 54 (2024) 398–405 Carvalho et al. / Structural Integrity Procedia 00 (2019) 000 – 000

403

6

all L O due to its inherent brittleness. Notably, DAJ consistently demonstrates higher P m values compared to SAJ. In cases of L O =12.5 mm and 25 mm, this difference is substantial, reaching 14.4% and 22.9% respectively, when comparing the best SAJ (2015 for L O =12.5 to 37.5 mm, and 7752 otherwise) with the corresponding DAJ (7752-2015 7752). However, as L O increases, the difference decreases to 4.0% ( L O =37.5 mm) and 0.4% ( L O =50 mm) due to adherend plasticization, which can favour SAJ by simplifying the manufacturing process. The  P m values often exceed 100%, except for joints with L O =12.5 mm. Regarding the 25/50/25 DAJ (Figure 5b) the variants yielding the highest P m are the 7752-AV-7752 DAJ ( L O =12.5 mm), 2015-AV-2015 DAJ ( L O =25 mm), and both 7752-2015-7752 and 7752 AV-7752 DAJ configurations ( L O =37.5 mm and 50 mm). Similar to the previous analysis, SAJ using the AV138 adhesive displays the lowest P m across all L O . Independently of L O , DAJ is consistently recommended over SAJ due to superior P m performance. The best DAJ configuration (7752-2015-7752 for L O =12.5 to 37.5 mm, and 7752 otherwise) exhibits percentile improvements of 5.6% ( L O =12.5 mm), 10.6% ( L O =25 mm), 3.6% ( L O =37.5 mm), and 0.4% (attributed to adherend plasticization, L O =50 mm).  P m values, much like the prior analysis, frequently exceed 100%, except for the joint configuration with L O =12.5 mm, emphasizing the advantage of DAJ. When analysing the 33/34/33 DAJ configuration (Figure 5c) it can be stated that this configuration consistently reveals superior P m results for all L O cases. Specifically, the 2015-AV-2015 DAJ ( L O =12.5 and 25 mm) and both 7752-2015-7752 and 7752-AV 7752 DAJ configurations ( L O =37.5 and 50 mm) provide the best P m solutions. Conversely, the AV138 SAJ represents the worst-case scenario across all L O due to its inherent properties. Comparing the best-performing SAJ (2015 for L O =12.5 to 37.5 mm, and 7752 otherwise) with the corresponding DAJ configuration, the relative P m improvements for DAJ are 14.0% ( L O =12.5 mm, 2015-AV-2015 DAJ), 11.9% ( L O =25 mm, 2015-AV-2015 DAJ), 4.0% ( L O =37.5 mm, 7752-2015-7752 DAJ), and 0.4% (due to adherend plasticization, L O =50 mm, 7752-AV-7752 DAJ).  P m values exhibit patterns similar to previous DAJ configurations, further highlighting the technique's advantage. Overall significant differences are evident up to L O =25 mm for DAJ. Beyond this point, adherend plasticization assumes a crucial role in the failure process, resulting in negligible differences in P m between different DAJ configurations. Specifically, the 12.5/75/12.5 DAJ configuration yields the highest P m for L O =12.5 and 25 mm, while the 33/34/33 DAJ configuration yields the lowest. The minimum P m difference compared to other configurations is 9.9% for L O =25 mm, with minimal variation observed for L O =12.5 mm. 3.3. Failure energy The failure energy ( U ) is obtained numerically through the estimation of the area beneath the load-displacement ( P -  ) curves to failure of each specimen. In order to facilitate comparison between configurations, the percentile U variations (  U ) in relation to the benchmark configuration (AV138 SAJ) are also assessed. In Fig. 4 is shown U as function of L O for SAJ and DAJ (12.5/75/12.5 (a), 25/50/25 (b) or 33/34/33 (c)) configurations. The discussion about U is categorised by DAJ configurations and followed by comparisons. For the 12.5/75/12.5 DAJ Configuration (Fig. 4 a) the 7752 SAJ ( L O =12.5 mm), 7752-2015-7752 DAJ ( L O =25 mm), and 7752-AV138 7752 DAJ ( L O =37.5 and 50 mm) exhibit the highest U values. AV138 DAJ presents more modest results due to brittleness, similarly to other DAJ configurations. While L O =12.5 mm favours SAJ with a 5.7% improvement over 7752-2015-7752 DAJ, other L O values benefit from the DAJ concept, particularly the 7752-AV138-7752 DAJ with larger L O . Notably, the difference between the best DAJ (7752-AV138-7752) and best SAJ (2015) for L O =37.5 mm is notably significant, with a 178.8% improvement. Regarding the 25/50/25 DAJ configuration (Fig. 4 b), optimal U results align with the 7752 SAJ ( L O =12.5 mm), 7752-2015-7752 DAJ ( L O =25 and 37.5 mm), and 7752-AV138-7752 DAJ ( L O =50 mm), which is similar to the former DAJ configuration results. Despite recommendations, DAJ proposals consistently outperform SAJ solutions. The 7752-2015-7752 DAJ at L O =12.5 mm is only 4.3% lower than the optimal SAJ. The largest DAJ/SAJ difference emerges at L O =37.5 mm, with a 140.0% variation. In particular, U undergoes significant variations between L O =37.5 and 50 mm, which distinguishes it from other DAJ configurations. In the case of 33/34/33 DAJ configuration (Fig. 4 c), the same SAJ (7752) yields the best U predictions. For other L O values, the 7752-2015-7752 DAJ ( L O =25 and 37.5 mm) and 2015-AV-2015 DAJ ( L O =50 mm) offer superior U values. Convergence of U values is evident among all DAJ configurations, resulting in no distinct recommendation. While the relative advantage over the best DAJ is generally small, up to 30.2% for L O =37.5 mm, the DAJ with this adhesive ratio lacks significant advantage. Overall DAJ configuration comparison, the three DAJ configurations reveals differences between the 33/34/33 DAJ and the other two DAJ ratios, primarily prominent for L O =37.5 mm. The