PSI - Issue 83

R.J.B. Rocha et al. / Procedia Structural Integrity 83 (2026) 187–195

192

adherend failure was observed with 2015, and a similar pattern was seen with 7752 for L O =10 and 20 mm, whereas for L O =5 mm, cohesive failure occurred within the adhesive. Table 3 compares the experimental and numerical failure modes for all tested joint architectures (adherends, adhesives, and L O ). Overall, experimental failure modes were accurately predicted. However, results from SLJ with PLA and 2015 revealed a discrepancy, as experimental failure occurred in the adherends instead. This divergence is likely attributable to defects inherent to AM, such as insufficient fusion between internal layers, which can lead to premature failure of the adherends. In the case of ABS adherends, numerical models indicated that all joints failed in the adherends for both adhesives, except for the SLJ configuration using 7752 with L O =5 mm, where a different failure mode was observed.

Table 3. Experimental vs. numerical failure mode comparison with all tested configurations.

L O [mm] Analysis

PLA EXP Adh Adh Adh Coh Coh Coh Adh Adh Adh Coh Coh Coh

ABS EXP Adh Adh Adh Adh Adh Adh Adh Adh Adh Adh Adh Adh

PETG

Adhesive

Joint architecture

NUM

NUM

EXP Adh Adh Adh Adh Adh Adh Adh Adh Adh Adh Adh Adh

NUM

5

Coh Coh Coh Coh Coh Coh Adh Adh Adh Coh Coh Adh

Adh Adh Adh Coh Adh Adh Adh Adh Adh Adh Adh Adh

Adh Adh Adh Coh Adh Adh Adh Adh Adh Adh Adh Adh

2015

10 20 10 20 10 20 10 20 5 5 5

SLJ

7752

2015

SJ

2015

Adh – adherend failure; Coh – cohesive failure in the adhesive

3.2. Joint strength The strength was evaluated from the maximum load ( P max ). Three L O =5, 10 and 20 mm were tested for SLJ and SJ. Fig. 5 shows experimental and numerical P- δ curves for the best combination (PLA/2015) at L O =10 and 20 mm. The SLJ exhibits higher initial stiffness and a more linear response up to P max , with a clear benefit from longer L O . In contrast, SJ display an earlier deviation from linearity and slightly lower P max at L O =20 mm due to additional peel stresses at the step transition. The CZM predictions accurately capture both the stiffness and the failure points. The evolution of the average experimental P max with L O for the SLJ geometry is presented in Fig. 6. Joint strength increases with L O when using the 2015, reaching the highest values with PLA (approximately 2.53 kN at L O =20 mm). The 7752 produces lower absolute loads but allows greater  before failure, particularly beneficial for the ductile ABS and PETG adherends. Failure in longer SLJ specimens often shifts to the adherend for the strongest combinations.

a)

b)