3D Printing of polymer composites with material jetting: Mechanical and fractographic analysis

Abstract Material jetting technology is gaining popularity due to its distinctive capability to produce multi-material parts by UV curing in a single process. A unique composite behavior with improved mechanical properties can be achieved due to the ability to spatially vary the composition of hard and soft photopolymer. This characteristic is exceptionally favorable in the fabrication of soft robotics and 4D printed parts, which motivated the study of geometrical analysis and the mechanical analysis of the 3D printed composite structure. The present work initiated with visual analysis of micro composites to better understand the dimensional accuracy of the PolyJet technology. It is shown that geometric resolution is reasonable with feature size larger than 500 µm. The mechanical behaviors of 3D printed polymeric composites with different compositions and arrangements of reinforced particles are investigated. When subjected to compression, it is found that orientations and geometries of reinforced particles affect the stiffness of the composite. Digital material tensile testing results show that samples oriented at 45° on the build platform have a lower ultimate tensile strength and elongation at break than samples oriented in a parallel direction. Composite tensile testing results reveal that with a 5% volume fraction of reinforced particles, print orientation has no significant effect on strength. However, the composition and arrangement of particles greatly affect the behavior of the samples. Fractographic analysis is then conducted on the fractured surface of the tensile samples using scanning electron microscopy. It is found that hard particles strengthen the part, but soft particles serve as a crack initiation site.