Mechanical behaviour of 3D printed composite parts with short carbon fiber reinforcements

This study investigates the mechanical behaviour of 3D printed composite parts with short carbon fiber (SCF) reinforcements by conducting mechanical testing. Further, this study examines the relevance of the mechanics of traditional composite laminates for characterizing the mechanical behaviour of printed parts. Initially, test coupons were 3D printed with different layer thicknesses and printing directions. The test coupons were then subjected to mechanical testing. Test results reveal that the tensile properties of thin-layered printed parts are better than those of thick-layered printed parts, but not the interlaminar properties. Thick-layered parts performed poorly under tensile loads because of the presence of undesirable enclosed voids within the extruded fibers (extrudates). Further, laminate theory accurately predicted the mechanical behaviour of thin-layered bidirectionally printed parts. The failure surface followed the orientation of extrudates in unidirectionally printed parts. The micro-CT analysis unveiled microstructural features, such as the orientation of SCFs along the printing direction, the presence of enclosed voids within the extrudates of thick-layered parts, and a reduction in maximum length of SCF in thin-layered parts; such features influenced the final mechanical behaviour of the printed parts.