Additive manufacturing of short fiber oxide ceramic matrix composite: Process analysis and material properties

This work investigates the material extrusion-based additive manufacturing (AM) process chain of a pure alumina-based oxide ceramic matrix composite, starting from material selection, large-scale compounding to pellets, the AM process itself, debinding and sintering as well as microstructural and mechanical characterization. The compounded pellets have a volume share of 50% binder (polyvinyl butyral [PVB], polyethylene glycol [PEG], and stearic acid) and 50% alumina (Al₂O₃, alumina powder, and Nextel 610 alumina fibers) with an aimed fiber volume share of 40% after sintering. The material is compounded on an industrial scale with approximately 10 kg/h and the material extrusion-based AM process reaches speeds of up to 1000 mm/s. A variation of the feed rate leads to a significant increase in surface roughness and an increase in mass of 30%, in thickness of 12% and in width of 25%. The flexural behavior in the four-point-bending test can be described by a fast first peak and reaching higher flexural strength after the first crack subsequent with averages of 23.8 ± 3.6 MPa below .1% elongation. The fracture surfaces show the expected failure mechanisms like pull-out and crack deflection. The resulting fiber length in the printed samples is 140 µm in average.