By Geoff Giordano
The use of carbon fiber to improve the fracture toughness of 3D-printed fused filament fabricated carbon fiber/ABS composites was effective in loadings up to 25 percent, according to research detailed in a May 10 ANTEC® presentation. Optimal results were achieved with 10 percent carbon fiber load.
Karun Kalia, a PhD candidate in the plastics engineering department at the University of Massachusetts, Lowell, studied the effect of adding chopped discontinuous carbon fiber (CF) to ABS. A CF/ABS part was shown to possess higher tensile strength and modulus and lower residual warpage than a neat ABS part, he said. However, carbon fiber as a raw material is expensive and can wear out printing nozzles, he noted.
Kalia extruded CF/ABS filament comprising ABS Terluran GP-35 and Zoltek CF PX35 and printed specimens on a Felix Pro-2 unit. Fracture testing was conducted on an Instron 5966 machine at 10 mm per minute according to the ASTM D5045 standard.
Raster lines disappeared in trials of CF/ABS composites printed by fused filament fabrication with 15 percent carbon fiber loading. Courtesy of Karun Kalia/University of Massachusetts, Lowell
Testing carbon fiber loadings of zero, 10, 15, 20 and 25 percent, Kalia said that “there are two competing mechanisms … a decrease in the inter-bead voids and an increase in the intra-bead voids. However, intra-bead voids will be more detrimental because [this] can create more stress concentration points, and therefore provide lower fracture toughness.” At optimal print settings, a reduction in inter-bead void dominated, and therefore provided relatively higher fracture toughness.
Comparing his work to studies published by others, Kalia noted that lines that appeared between rasters in his sample prints at zero percent CF loading disappeared at 15 percent, whereas those lines remained under the same conditions in a previous evaluation. He suggested that his use of low-viscosity ABS resin and optimization of the fused filament fabricated process could be the reason.
“With proper choice of ABS grade, and optimized process parameters, carbon fiber/ABS composites can be made up to 25 weight percent of carbon fiber loading without any drop in the fracture toughness,” Kalia concluded. His ongoing research will include quantitative analysis of inter- and intra-bead voids and the effect of fused filament fabricated process parameters and print configurations on fracture toughness.
Kalia’s presentation “Effect of Carbon Fiber on the Fracture Toughness of Fused Filament Fabricated CF/ABS Composites” will be available on demand to ANTEC® attendees and those who register for access after the conference.