Characterization of 3-D Printed Parts

Aerospace, automotive, medical, and many other industries are finding applications for 3-D printing of plastic parts, the primary advantages including fast turnaround when custom design is required (no need to fabricate a mold) and ability to manufacture nested parts. However, the Achilles heel for such processing is the low z-axis strength of the printed objects. The goal of this research is explore the characterization of compatibilized polymer blends of ABS and nylon on z-axis mechanical properties of 3-D printed parts. Experiments were carried out on two scales, the small scale being a MakerBot 2X Replicator, and the large scale being a â??big area additive manufacturingâ? or BAAM printer located at Oak Ridge National Labs Manufacturing Demonstration Facility. In both cases a commercial ABS material was compounded with a compatibilizer, poly(styrene-maleic anyhydride) (SMA), and then compounded with the nylon. Tensile testing for the Makerbot scale samples showed that the Z axis modulus of the ABS decreased by over 12% on addition of up to 20% (w/w) SMA, but the X axis modulus was maintained. Several compatibilized nylon blends were made from nylon(60%)/ABS(40%)/SMA(5-20%) (w/w) and the modulus was tested in the x-direction print. The tensile testing for the compatibilized nylon showed an increase of the modulus for the 5% and 20% (w/w) mixtures with the 5% (w/w) mixture showing a modulus increase of 172%. Flexural testing (4 point bend) for the Blue Gantry scale samples showed that the X axis modulus of the polyamide (PA)/ABS/SMA blend increased on addition of ABS/SMA (200%) as compared to the base nylon X axis modulus. The fracture sites of the nylon materials were dull for all samples tested in the X axis direction. For those samples tested in the Z axis direction, some glossy features were noted in the fracture surface. Results for Charpy impact testing will be discussed as well. Characterization of the interfaces of printed parts will be discussed as well as novel failure modes.