Advantages of in-situ impregnation 3D printing in continuous flax/PLA biocomposites for optimized mechanical properties in structural applications

The in-situ impregnation 3D printing technique offers a unique advantage over traditional composite manufacturing methods: the ability to control fiber weight fraction within a single print. This study demonstrates this capability through the printing of continuous flax fiber-reinforced PLA biocomposites. A parametric study was conducted to determine the optimal printing parameters, including nozzle temperature and cooling fan usage. Subsequently, samples with four different fiber weight fractions (0, 30, 40, and 50 wt%) were printed using the optimized parameters. Tensile properties were evaluated through both tensile testing and acoustic impulse measurements, while Shore D hardness, density and porosity were also assessed. The results reveal a significant improvement in tensile properties and an increase in density with increasing fiber weight fraction, accompanied by a decrease in Shore D hardness. Additionally, the choice of printing pattern, influences the tensile properties and damage mechanisms. These findings highlight the potential of in situ impregnation for producing custom fiber-reinforced biocomposites with tailored mechanical properties at a low cost.