Abstract: In order to improve the mechanical properties of the carbon fiber composites prepared by the hand lay-up molding process, the fiber cloth was pretreated with various parameters of ultrasound before curing, and the specimens were tested in bending and tension after curing and molding. The effects of various ultrasonic times and powers on the mechanical properties of the hand lay-up molded carbon fiber composites were investigated by using digital image correlation (DIC) and scanning electron microscope (SEM) for characterization. The results showed that the bending and tensile loads of the specimens were 854.02 N and 31 351.10 N, respectively, when the ultrasonic time was 15 min and the ultrasonic power reached 300 W. The bending and tensile strengths of the specimens increased by 32.05% and 25.39%, respectively, compared with those of the un-sonicated specimens. At this sonication parameter, both the range of strain value variation and the number of voids were significantly reduced compared to the specimens without sonication. This indicates that ultrasonic vibration-assisted hand lay-up molding can effectively reduce the stress concentration phenomenon and the generation of voids, thus improving the mechanical properties of the prepared materials.

Key words: water immersion ultrasound, hand lay-up process, mechanical properties, DIC, SEM, composites