Additively manufactured beam-to-column connections for assembly of pultruded GFRP members: experimental investigation and fracture-based numerical modelling

The structural performance of pultruded glass fiber–reinforced polymer (GFRP) systems is strongly governed by the efficiency of their connections, which often represent the most critical components of composite structures. Conventional bolted joints, largely adapted from steel construction, introduce stress concentrations and material degradation due to drilling, compromising the brittle composite material and limiting load redistribution. In this context, 3D-printed components offer a promising alternative, enabling contact-based solutions that avoid perforations while providing geometric flexibility and manufacturing efficiency. This study investigates the mechanical behavior of 3D-printed beam–column connectors for pultruded GFRP profiles, focusing on fused filament fabrication (FFF) parameters, including infill pattern, raster orientation, and build direction. The ‘Cubic’ infill pattern, characterized by a three-dimensional interconnected architecture, provided superior performance by promoting uniform stress distribution and delaying crack initiation. The best-performing configuration, Cubic_XY_90°— combining the Cubic infill pattern, printing in the XY build orientation, and a 90° raster angle — reached a load-carrying capacity approximately 68% higher than the best-performing configuration with a unidirectional Line infill pattern. A framework coupling the extended finite element method (XFEM) with a cohesive zone model (CZM) was developed to simulate damage initiation and crack propagation. The model showed excellent agreement with the experiments, reproducing peak load and initial rotational stiffness with differences of 0.6% and 3.1%, respectively. The findings demonstrate the structural feasibility of 3D-printed components for pultruded GFRP systems and provide insight into their governing failure mechanisms.