Reinforcement of material extrusion 3D printed polycarbonate using continuous carbon fiber

Additive manufacturing (AM) technologies are capable of fabricating custom parts with complex geometrical shapes in a short period of time relative to traditional fabrication processes that require expensive tooling and several post processing steps. Material extrusion AM, known commercially as Fused Filament Fabrication (FFF) technology, is a widely used polymer AM process, however, the effects of inherent porosity on mechanical strength continues to be researched to identify strength improvement solutions. To address the effect of porosity and layer adhesion on mechanical properties (which can sometimes result in 27-35% lower ultimate tensile strength when compared to plastic injection molding), an approach was employed to reinforce 3D printed polycarbonate (PC) parts with continuous carbon fiber (CF) bundles. ASTM D638 Type I specimens were fabricated with printing interruptions to manually place and embed CF bundles. Specimens contained either one, two, or three layers of embedded CF bundles. Results demonstrated a maximum of 77% increase in tensile yield strength when PC was reinforced with three CF bundles and micrographs showed multiple regions with zero porosity due to the CF inclusion. PC with three bundles of CF (modulus of 3.36 GPa) showed 85% higher modulus of elasticity than the neat PC specimens (modulus of 1.82 GPa). The manual placement of CF and its impact on mechanical properties motivated the development of an automated selective deposition method using an ultrasonic embedding apparatus. Substantial technology development towards the embedding process of continuous carbon fiber bundles using ultrasonic energy was achieved in an automated fashion which is complementary of digital manufacturing and novel when compared to other existing processes.