Mechanical properties enhancement of 3D-printed HA-PLA composites using ultrasonic vibration assistance

3D-printed HA-PLA composites have attracted much attention because of their excellent biodegradability and osteointegration properties. However, HA particles negatively affect the mechanical properties of the composite parts. In this study, ultrasonic vibration-assisted 3D printing was used to improve the mechanical properties of HA-PLA composite specimens, and the effects of different infill angles and ultrasonic vibration power on the mechanical properties were investigated. The results demonstrated that the degradation and anisotropy of the mechanical properties of HA-PLA composites were alleviated by the use of ultrasonic vibration. By applying the ultrasonic vibration, the tensile and flexural strengths of the 20 wt% HA-PLA specimens fabricated with a 90 degrees infill angle demonstrated the largest improvement of 104.3% and 112.7%, respectively. The high-frequency ultrasonic vibration waves promoted the spreading and fusion of the extruded materials, thereby reducing overlapping voids within the specimens and improving the interface bonding strength, also facilitated the refinement and dispersibility of the HA particles, which inhibited the formation of stress concentrations within the specimens and ultimately improved the mechanical properties. The printing process developed in this study can also be adapted to other particle (or other reinforcement types) reinforced composite to improve their mechanical performance.