PSI - Issue 83

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

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1. Introduction The fabrication of three-dimensional (3D) objects, initially a niche technique for rapid prototyping in the 1980s, has evolved into a robust manufacturing approach. AM, commonly referred to as 3D printing, is now a viable solution for functional components in diverse industries (Zhou et al. 2024). AM provides freedom in the design and fabrication of complex geometries that are unattainable through conventional manufacturing. Currently, Fused Deposition Modelling (FDM) is the most widely adopted AM technology. In this process, thermoplastic filament is melted through a heated nozzle and extruded in continuous strands. These strands are deposited layer by layer onto a build platform, where they solidify to form a 3D object (Zhou et al. 2024). FDM primarily employs thermoplastic polymers, such as PLA, ABS, and PETG. Alternative technologies, such as Selective Laser Sintering (SLS), enable the processing of a wide range of materials, including metals, ceramics, and composites (Attaran 2017). Despite the significant development of AM technologies, AM parts often exhibit anisotropic behavior, as their mechanical properties depend on the build orientation (Zhou et al. 2024). Moreover, component size is constrained by the build volume of the printing system, meaning that large structures must often be manufactured as multiple subcomponents and assembled afterwards (Attaran 2017). Several joining methods have been developed. Integral fits represent the cheapest and fastest approach, although they are susceptible to material creep (Klahn et al. 2016). Mechanical fasteners introduce significant stress concentrations (König et al. 2022). Friction stir welding produces high quality joints with low energy requirements, yet the joints are often weaker than the base material (Tiwary et al. 2020). Adhesive bonding enables a more uniform stresses and provides a good vibration absorption (Ribeiro et al. 2024). Nevertheless, adhesive bonding commonly requires careful surface preparation to achieve a strong bond (Khosravani et al. 2021). The performance of adhesively-bonded AM joints is dictated by a complex combination of parameters associated with both the process and the bonding procedure. AM parameters that directly affect the strength include build orientation, printed layer thickness, and surface morphology. Similarly, the adhesive joint performance is strongly influenced by parameters such as adhesive layer thickness, surface treatment, and joint geometry (Atahan and Apalak 2022). A common numerical method employed to simulate the behavior of adhesive joints is CZM, which uses a traction-separation law to describe the relationship between the stress applied to the adhesive and the relative displacement of the joined parts (Manoj et al. 2024). CZM can be a crucial element in joint design optimization, allowing for the virtual testing of several joint geometries without the need for experimental trials. Khosravani et al. (2021) investigated the influence of printing parameters and adhesive thickness on the structural integrity of joints manufactured with 3D-printed PLA adherends. Using CZM, the authors identified 0.2 mm as the optimum adhesive thickness ( t A ) to maximize tensile strength. Öztürk et al. (2024) introduced a new approach that combines CZM with the Hill yield criterion in the study of SLJs with polycarbonate substrates, therefore being able to account for material anisotropy. Ribeiro et al. (2024) evaluated the tensile performance of adhesively bonded SLJs using PLA, PETG and ABS adherends. The work compared experimental results with CZM predictions, thereby validating the predictive accuracy. Atahan and Apalak (2022) studied the effects of loading rates on SLJs with PLA adherends, using digital image correlation to analyze how peeling and shear strains concentrate around the free edges of adherend-adhesive interfaces during tensile tests. The work provided data on tensile loading behavior of bonded joints. The presented study combines experimental testing and numerical modelling to evaluate the tensile performance of adhesively bonded joints in AM structures. SLJ and SJ configurations were manufactured using PLA, PETG, and ABS adherends, and bonded with two structural adhesives. Tensile experiments were carried out to characterize the joint strength and failure mechanisms. In parallel, CZM simulations were developed to replicate the experimental response.

2. Materials and methods 2.1. Adherends and adhesives

PLA, PETG, and ABS filaments were selected as adherends. PLA is the most widely used raw material in extrusion based AM, owing to its biocompatibility, biodegradability, mechanical strength, and processability (Pandey et al. 2020). PETG has been used to replace traditional polymers due to its chemical resistance, mechanical performance, and flexibility (Valvez et al. 2022). ABS is the most comprehensively researched thermoplastic materials used in FDM (Ahmad and Yahya 2023). Due to different manufacturing procedures, an Ender 3 Max 3D printer was used to produce