Interfacial fracture characterization of multi-material additively manufactured polymer composites

In this study, a comprehensive experimental investigation is performed to observe the influence of printing process parameters on the interfacial fracture toughness of bi-material additively manufactured composites. A single leg bending (SLB) specimen made of Polylactic acid (PLA) and Nylon is loaded under the quasi-static three-point bending condition to initiate the fracture between the PLA/Nylon interface. Six different process parameters (bed temperature, printing temperature, printing speed, printing orientation, layer height, and thickness ratio) are considered to investigate the fracture toughness. It is observed that process parameters have a significant impact on the bi-material interfacial fracture toughness. Due to the increase of crystallinity of the polymer, the fracture toughness decreases by about 40% when the bed temperature increases from 60 °C to 100 °C. However, with improved molecular diffusion, the fracture toughness is enhanced by 95% with the increase of the printing temperature. Although printing speed has not any significant impact on fracture toughness, thinner layers provide a better bond strength and polymer wetting, resulting in a higher fracture initiation toughness compared to thicker layers. Due to the presence of extra voids and anisotropic behavior, the specimens of 0o/90o raster-orientation demonstrate about 75% lower fracture toughness compared to those of +45o/-45o orientated specimens