Porosity in multi-axis material extrusion of short-fibre composites

This study aims to investigate the relationship between part porosity and mechanical properties of short-fibre reinforced polylactic acid printed via multi-axis material extrusion (MAMEX) to establish guidelines for optimal process configurations.

Material properties graphs provide the basis for studying the relationship between porosity and mechanical behaviour. Using the correlations found in this study, the way to improve printing strategies and filament properties can be deducted directly from an analysis of the print path and the final influence on mechanical performance.

Some commercial brands of short-fibre reinforced filament present inherent porosity that weakens the mechanical behaviour of MAMEX components.

Low-cost MAMEX allows the production of components that do not present anisotropic behaviour and are mechanically optimised through the alignment of the filaments along with internal stresses. This paper also addresses the effects of multi-axis deposition strategies on the resulting porosity and proposes improvements to reduce residual porosity, thus increasing the mechanical performance in the future.