Bending strength of adhesively-bonded 3D-printed polymer structures

Often referred to as three-dimensional (3D) printing or 3DP, additive manufacturing (AM) is a growing alternative to conventional fabrication methods such as injection moulding and machining. Rapid prototyping, improved material efficiency, and the ability to create extremely complex geometries are some of its key advantages. Size constraints in AM components, however, continue to be a significant drawback, requiring the joining of smaller printed components to produce complex structures. This study uses additively manufactured polymeric adherends, namely Acrylonitrile Butadiene Styrene (ABS), Polyethylene Terephthalate Glycol-modified (PETG), and Polylactic Acid (PLA), to investigate the structural behaviour of single-lap joints (SLJ) under four-point bending (4PB). Araldite® 2015 and Sikaforce® 7752 adhesives were used to obtain the bonded joints. Experimental testing was used to determine the adherends’ mechanical characteristics, such as their elastic modulus, plastic deformation characteristics, and fracture behaviour. Failure modes, maximum load ( P m ), joint stiffness ( k max ), and energy absorption ( E max ) were assessed by means of an experimental campaign. The results were compared to predictions made by a Cohesive Zone Model (CZM). The findings highlight how adherend material, adhesive type, and overlap length ( L O ) all significantly affect joint performance. The Sikaforce® 7752/PLA combination exhibited the highest P m and E max (161 N and 1.58 J, respectively), while PLA bonded with the Araldite® 2015 showed the highest k max (10.29 N/mm), in all cases with the highest L O studied of 20 mm.