A pedestrian bridge manufactured entirely from pultruded GFRP began developing visible longitudinal cracks months after installation. Visual inspection failed to determine the origin of the failure. A three-dimensional analysis using digitized ultrasound was employed to map the interior of the beams, revealing extensive areas with lack of resin impregnation in the core of the profile.
Workflow: Scanning, Inspection, and Simulation in nCode 🔬
The technical process began with capturing volumetric data using a synchronized array of ultrasonic transducers, generating a three-dimensional point cloud of the material's interior. This cloud was imported into GOM Inspect to align the nominal CAD model with the actual defect geometry. Resin voids up to 8mm in length were identified in the central zone of the beam. Subsequently, a finite element mesh was exported to Siemens Simcenter, where orthotropic properties of the GFRP were assigned. The model was loaded with cyclic pedestrian traffic boundary conditions. Finally, the stress history was transferred to nCode DesignLife to perform a multiaxial fatigue analysis, predicting a 60% reduction in service life due to stress concentration at the edges of the voids.
Implications for Quality Control in Pultrusion ⚙️
The methodology demonstrated that the failure was not due to poor structural design, but to an internal manufacturing defect. The lack of impregnation acts as an internal notch that initiates delamination under repeated bending loads. This case validates the need to integrate 3D volumetric inspection systems and fatigue simulation into the production line of pultruded profiles, allowing critical areas to be detected before commissioning.
Which finite element simulation methodologies allow for more accurate prediction of delamination propagation in pultruded GFRP profiles under cyclic fatigue loads?
(PS: Material fatigue is like yours after 10 hours of simulation.)