Fiber orientation and volume fraction of particles in 3D printing materials affect strength and quality

Glass or carbon fibers are often added into 3D printed materials to improve their thermomechanical properties. With applications ranging from medical to aeronautical, it is important to understand how the addition of particles can affect 3D printing.

Not only do the particles themselves affect the mechanical and thermal properties of 3D printed materials, but their orientation and volume fraction do too. Ouyang et al. present a numerical study, which considers the effects of fiber orientation, temperature and the deformation caused by non-isothermal 3D printing. To do so, they use a smoothed particle hydrodynamics method common to studies on computational fluid dynamics.

“Our approach is built on classical equations of fluid mechanics, heat transfer and a model, which describes the evolution of a fiber microstructure in a fluid flow,” said author Boo Cheong Khoo. “Such numerical simulations can be useful to investigate and understand certain phenomena occurring during 3D printing that one cannot observe experimentally.”

The authors demonstrated if fibers are aligned with the printing direction, they enhance the thermal conductivity and tensile strength of the final composite.

The volume fraction of the fibers can impact either positively or negatively. A higher volume fraction improves composite properties but can also clog the nozzle and introduce voids in the product.

“In the future, a fiber orientation-dependent thermal conductivity model will be implemented to provide a more accurate description of the composite thermal conductivity. Also, we hope to extend the 2D simulations performed to three dimensions by means of parallel computing,” Khoo said.

Source: “A smoothed particle hydrodynamics simulation of fiber-filled composites in a non-isothermal three-dimensional printing process,” by Zhenyu Ouyang, Erwan Bertevas, Laetitia Helene Parc, Boo Cheong Khoo, Nhan Phan-Thien, Julien Férec, and Gilles Ausias, Physics of Fluids (2019). The article can be accessed at https://doi.org/10.1063/1.5130711 .