Degradation characteristics of 3D printed continuous fibre-reinforced PA6/chopped fibre composites in simulated saltwater

This paper investigates the performance of continuous fibre-reinforced 3D printed components in salt water medium at room temperature. Markforged (R) Mark Two 3D printer was employed to fabricate standard specimens made of Onyx and reinforced Onyx specimens with continuous carbon, high-strength high-temperature glass, and Kevlar fibres. Aging process was conducted to characterize the long-term effect of salt water on the mechanical behaviour of fibre-reinforced 3D printed samples. Several mechanical tests including tensile, 3-point bending test and indentation testing have been carried out on the dry and aged standard samples to evaluate tensile strength, flexural strength, micro-hardness, and modulus of elasticity in micro-scale. The mechanical tests revealed the degradation and loss in mechanical properties of the printed samples after aging in salt water. The data highlighted that Onyx samples without continuous fibres experienced the most significant reduction in both tensile (33.54%) and flexural (63.47%) strengths after 1 year, while continuous carbon fibre-reinforced Onyx samples showed comparatively lower strength reductions (28.46% in tensile strength and 18.73% in flexural strength). Optical and scanning electron microscopy were performed to investigate the fracture behaviour of the tested specimens. In addition, the DSC assessment showed a slight change in the thermal properties of aged specimens.