Sandwich printing of PLA and carbon fiber reinforced-PLA for enhancing tensile and impact strength of additive manufactured parts

Abstract

The tensile and impact strength of the additively fabricated polylactic acid (PLA)-based components are enhanced by adding reinforcements like carbon fiber, glass fiber, ceramics, etc. Reinforcing PLA with short carbon fiber enhances the mechanical properties to a limited range. The fused deposition modeling (FDM) fabricated from composite materials often exhibits weak bonding between layers. This article focuses on enhancing the interlayer bonding by employing a novel sandwich printing technique while also aiming to reduce the amount of reinforcement material required. The FDM dual-extruder printer is used to prepare samples with reinforcement volumes of 20 %, 40 %, 60 %, 80 %, and 100 %, consisting of alternating layers of PLA‑carbon fiber (CF) and PLA. Thermal and mechanical characterizations were conducted, and failure surfaces were evaluated using field emission scanning electron microscopy (FESEM). The results demonstrate that sandwich printing with 80 % PLA-CF and PLA increases tensile strength by 17.06 %, tensile modulus by 27.48 %, impact strength by 8.01 %, and hardness by 38.53 % compared to full PLA-CF reinforcement. The penetration of carbon fibers and the reduction of voids at layer junctions are responsible for the enhancement in mechanical properties. The alignment and orientation of fibers along the printing direction improve bonding and load-bearing capacity of the printed specimens. Compared to full reinforcement, the flexural strength for 60 % sandwich layers of PLA-CF and PLA increased by 18.76 %. These results confirm that sandwich printing enhances mechanical strength.