Effect of Extrusion Parameters on Short Fiber Alignment in Fused Filament Fabrication

Abstract

Additive manufacturing by material extrusion such as the widespread fused filament fabrication is able to improve 3D printed part performance by using short fiber reinforced composite materials. Fiber alignment is critical for the exploitation of their reinforcing effect. This work investigates the influence extrusion parameters have on the fiber alignment by conducting set of experiments on the process parameters determining whether the flow under the nozzle is convergent or divergent. A strong impact of flow conditions during extrusion line shaping on the fiber alignment is observed and two extremes are tested which show a large difference in strength, stiffness and strain at break in tensile testing along the extrusion lines. From highest to lowest fiber alignment, strength is reduced by 41% and stiffness by 54%. Fiber misalignment also leads to inhomogeneous strain fields in the layers when tested perpendicular to the extrusion lines. It is demonstrated that material flow after the nozzle has a high impact on the material properties of short fiber reinforced 3D printed parts and needs to be considered in process design.

Additively Manufactured Composite Lug with Continuous Carbon Fibre Steering Based on Finite Element Analysis

“…The design considerations for MEX composite structures are based on the multiple layers of fibre-reinforced matrix [ 9 ]. The short fibres in each layer are straight and parallel to each other and mostly aligned in the printing direction, causing anisotropic material behaviour [ 10 , 11 ]. Optimising the fibre alignment within each layer to alternating orientation from point to point has not been adopted, albeit due to the nonavailability of necessary commercial tools.…”