Diffusion of moisture from voids in additively manufactured composites: Effect of printing patterns

Composite materials are widely used in marine environments, with hygrothermal ageing being the main factor affecting their structural integrity (Zhang et al., 2017). In additively manufactured (AM) composites, printing-induced voids are formed at the interfaces between printing beads as a result of the layer-by-layer deposition process, with void’s size dependent on printing parameters (Ivey et al., 2017). Such voids present additional paths for the water ingress into these materials. Kim and Seo (2023) demonstrated that outer-wall layers in 3D-printed composite specimens can significantly retard water diffusion. Therefore, the impact of printing patterns on water penetration into AM composites is a critical factor for the diffusion process, worth investigation. This study integrates experimental analysis with finite-element modelling to investigate water diffusion in AM composites. Polylactic-acid specimens with a line printing pattern were printed and aged in water, with the diffusion process monitored via weekly measurement of weight increments. Specimens were immersed in water with their printing orientations arranged either parallel or perpendicular to the water surface, allowing for the evaluation of the effect of printing patterns on moisture transport. Both experimental and modelling results demonstrate that printing orientation significantly affects water penetration. These findings highlight the necessity of reconstructing the internal structure of 3D-printed composites from G-code to accurately capture their diffusion behaviour.