Bending behavior of 3D printed continuous fiber reinforced composite sandwich cylindrical shells

Continuous carbon fiber reinforced composite sandwich cylindrical shells (CFRCSs) have been widely used in aerospace and automotive fields due to their excellent load-bearing performance. However, traditional manufacturing methods involve complex processes and expensive molds. This study uses 3D printing technology to manufacture CFRCSs with sinusoidal, triangular, and trapezoidal core. The sample surface and inside fiber distribution is inspected by the optical microscope and X-ray microscope, respectively. It is found that the samples have the defects of uneven resin distribution, fiber breaking, and fiber waviness. The bending behaviors of CFRCSs are investigated by the three-point bending test. The results show that the CFRCSs with sinusoidal core have the maximum ultimate load of about 3094 N, while those with the triangular core structure have the minimum ultimate load of about 1774 N. The triangular and sinusoidal structures mainly undergo debonding at the junction of the core and the panel and fracture at the core because of the small contact area between the core and panel. In contrast, the trapezoidal structure is mainly brittle fracture with fiber pull-out at the bottom panel and fracture at the top panel. The core type greatly influences the bending mechanical properties of the printed CFRCSs. 3D printing technology can be used to manufacture CFRCSs with required mechanical properties by flexibly designing the core shape.