Fiber-Orientation Modeling During Extrusion-Based 3D Concrete Printing (2022-05)¶

Fibers tend to align in printing direction during fiber-reinforced 3D-concrete-printing processes, which allows for the orientation of the fibers in desired directions by controlling the printing process. This enables the production of components with advantageous fiber orientation states, which is not possible with conventional casting methods to this extent. To understand correlations between fiber orientation and process (e.g. printing speed or flow rate) and geometric (e.g. extrusion nozzle size and shape) parameters during the printing process, a fiber orientation model is implemented into a framework based on the Particle Finite Element Method (PFEM) to simulate extrusion processes during fiber-reinforced 3D-concrete-printing. The fiber orientation model is based on a representation using a second order orientation tensor, which is combined with an anisotropic Bingham viscsosity constitutive law and upscaling relations for the viscosity and yield stress from literature. A robust PFEM-compatible implementation of the fiber orientation model is proposed and verified using different convergence and parametric studies. Numerical analyses of fiber-reinforced 3D-concrete-printing in 2D revealed that fibers tend to align stronger in printing direction for larger printing speeds, smaller extrusion nozzles and smaller fiber aspect ratios.