PSI - Issue 83

R.J.B. Rocha et al. / Procedia Structural Integrity 83 (2026) 179–186

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2. Materials and methods 2.1. Joint materials

The adherends were manufactured by FDM using PLA, PETG, and ABS. These materials were selected due to their commercial availability and compatibility with structural adhesives. Printing was performed on an Ender-3 Max (PLA and PETG) and an Ender-6 (ABS) AM machines with the parameters listed in Table 1. Four bulk Type-I tensile specimens (ASTM D638), per material, were manufactured to characterize the adherend mechanical properties.

Table 1. Printing parameters for the adherends.

Parameter Layer height Infill density Wall thickness Print speed

PLA

PETG ABS

0.2 mm 0.2 mm 0.2 mm

50%

50%

50%

1.2 mm 1.2 mm 1.2 mm

75 mm/s

75 mm/s 230°C

120 mm/s

Nozzle temperature 215°C

230°C

Bed temperature 70°C Tensile tests were conducted on a Shimadzu Autograph AG-X 100 machine with a speed of 5 mm/min with a 50 mm gauge-length extensometer. Young’s modulus ( E ), tensile strength ( σ ₘ ), maximum strain ( ε ₘ ) were determined according to the EN ISO 527-1 standard. The obtained properties, average±standard deviation, are summarized in Table 2. PLA exhibited the highest E and maximum load ( P m ) but the lowest ε ₘ , while ABS showed the largest ε ₘ . 60°C 80°C

Table 2. Mechanical properties of the adherends (Ribeiro et al. 2024, Ribeiro et al. 2025). Property PLA PETG ABS P m (kN) 1419±16 1017±19 917±17 σ ₘ (MPa) 36±0.6 25±0.6 22±0.7 ε ₘ (%) 2.06±0.09 3.77±0.98 5.27±0.61 E (MPa) 2354±39 1362±210 1559±129 ν ( -) 0.36 0.40 0.37

Two structural adhesives with distinct behaviors were used: Araldite ® 2015 (two-part epoxy) and Sikaforce ® 7752 (toughened polyurethane). Relevant properties determined in previous investigations (Campilho et al. 2013, Faneco 2014) are provided in Table 3 (  m : shear strength, G IC : tensile fracture toughness, G IIC : shear fracture toughness). A 0.2 mm adhesive thickness layer, controlled by using a copper wire with 0.2 mm in diameter, was applied to the surfaces of the adherends. These joints were then clamped to avoid any relative movement during curing.

Table 3. Adhesive properties (Campilho et al. 2013, Faneco 2014).

Property E (GPa) σ m (MPa) ε m (%) τ m (MPa)

Araldite ® 2015

Sikaforce ® 7752

1.85±0.21 21.63±1.61 4.77±0.15 17.90±1.80 0.43±0.02 4.70±0.34

0.49±0.09 11.48±0.25 19.18±1.40 10.17±0.61 2.36±0.17 5.71±0.47

G IC (N/mm) G IIC (N/mm)

2.2. Geometry and test details

To examine the mechanical response of FDM-adherend SLJ and SJ subjected to 4PB loading, the experimental campaign considers PLA, ABS, and PETG adherends, bonded with the 2015 and 7752. The L O influence was assessed for 5, 10, and 20 mm. The joint geometry are depicted in Fig. 1 (a) for SLJ and (b) for SJ.