Material-Process-Property Relationships for Direct-Ink-Writing of Ceramic Matrix Composites

Ceramic matrix composites (CMCs) consist of a reinforcing secondary material phase within a ceramic matrix. These material systems can resist corrosive/oxidizing environments and have high hardness even at high temperatures. Among the two types of CMCs, ones featuring chopped fiber reinforcements offer simpler processing compared to the ones continuous fiber reinforcement systems. However, chopped fiber CMCs remain inferior to their continuous fiber counterparts in terms of mechanical and thermal properties [1]. This is primarily because the conventional processing methods generally lack control over the part microstructure and produce a randomly distributed reinforcement phase, limiting the achievable property enhancement. Emerging material extrusion-based additive manufacturing methods such as Direct-ink-writing (DIW) offer an exciting potential to address this issue. In DIW, highly viscous inks including ceramic matrix powders and reinforcing fibers are deposited layer-by-layer as they are extruded out of small capillaries. It has been shown that the high shear and extensional stresses experienced by the inks during this process can align the reinforcing particles along the printing direction [2,3], providing means to control final part microstructure.<br/> <br/>This study aims to understand the material-process-property relationships for DIW of CMCs including aluminum oxide matrix and chopped silicon carbide fiber reinforcements. Here, we formulate inks by combing aluminum oxide powder and silicon carbide fibers with a liquid phase polymer which is a precursor to silicon carbide. Through a custom DIW print head with integrated capillary rheometry [4] capability, we characterize the shear rates experienced by the inks during the printing process. We then examine the density, microstructure and mechanical properties of the printed and sintered CMCs to understand the influence of the DIW process on these outcomes. We expand the analysis to cover various ink compositions and nozzle sizes to explore the key material and process parameters to achieve microstructural control.<br/> <br/>References:<br/> <br/>[1] J. Binner, M. Porter, B. Baker, J. Zou, V. Venkatachalam, V.R. Diaz, A. D’Angio, P. Ramanujam, T. Zhang, T.S.R.C. Murthy, Selection, processing, properties and applications of ultra-high temperature ceramic matrix composites, UHTCMCs–a review, International Materials Reviews. 65 (2020) 389–444. https://doi.org/10.1080/09506608.2019.1652006.<br/>[2] J.W. Kemp, A.A. Diaz, E.C. Malek, B.P. Croom, Z.D. Apostolov, S.R. Kalidindi, B.G. Compton, L.M. Rueschhoff, Direct ink writing of ZrB2-SiC chopped fiber ceramic composites, Addit Manuf. 44 (2021) 102049. https://doi.org/10.1016/j.addma.2021.102049.<br/>[3] J.P. Lewicki, J.N. Rodriguez, C. Zhu, M.A. Worsley, A.S. Wu, Y. Kanarska, J.D. Horn, E.B. Duoss, J.M. Ortega, W. Elmer, R. Hensleigh, R.A. Fellini, M.J. King, 3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties, Sci Rep. 7 (2017) 43401. https://doi.org/10.1038/srep43401.<br/>[4] K.T. Estelle, B.A. Gozen, Complex ink flow mechanisms in micro-direct-ink-writing and their implications on flow rate control, Addit Manuf. 59 (2022) 103183. https://doi.org/10.1016/j.addma.2022.103183.