Additive manufacturing of multimaterial and multifunctional structures via ultrasonic embedding of continuous carbon fiber

Multimaterial and multifunctional parts were fabricated using an ultrasonic embedding technology in combination with 3D printing of thermoplastic. Continuous carbon fiber (CF) bundles were impregnated with polycarbonate solution (7 wt.%) prior to use in the embedding process. Using an ultrasonic embedding tool, a single layer of CF bundle was embedded into 3D printed polycarbonate parts containing one of three raster angles (RA): 0 degrees, +45/-45 degrees, and 90 degrees RA. In tensile testing, the highest ultimate tensile stress (UTS) was found in samples printed with +45/-45 degrees RA (75% higher UTS when compared to neat samples having the same RA), followed by those printed with 0 degrees RA (60% UTS increase). Samples printed with 90 degrees RA and containing a single layer (bundle) of embedded CF yielded the least UTS improvement (13%). Statistical t-test results showed that + 45/-45 degrees RA samples with embedded CF had superior mechanical strength while exhibiting less variation. Flexural testing of +45/-45 degrees RA specimens with embedded CF showed an average flexural strength increase of 7%, and an average modulus increase of 7% when compared to the neat specimen. In addition to the mechanical reinforcement, multilayer CF embedding using ultrasonic energy was demonstrated. In addition, the change in electrical resistance in embedded CF layers was measured during mechanical loading to demonstrate structural health monitoring functionality.