Direct ink writing of ceramic matrix composite structures

Abstract

We present the development of an ink containing chopped fibers that is suitable for direct ink writing (DIW), enabling to obtain ceramic matrix composite (CMC) structures with complex shape. We take advantage of the unique formability opportunities provided by the use of a preceramic polymer as both polymeric binder and ceramic source. Inks suitable for the extrusion of fine filaments (<1 mm diameter) and containing a relatively high amount of fibers (>30 vol% for a nozzle diameter of 840 lm) were formulated. Despite some optimization of ink rheology still being needed, complex CMC structures with porosity of~75% and compressive strength of 4 MPa were successfully printed. The process is of particular interest for its ability to orient the fibers in the extrusion direction due to the shear stresses generated at the nozzle tip. This phenomenon was observed in the production of polymer matrix composites, but it is here employed for the first time for the production of ceramic matrix ones. The possibility to align high aspect ratio fillers using DIW opens the path to layer-by-layer design for optimizing the mechanical and microstructural properties within a printed object, and could potentially be extended to other types of fillers. K E Y W O R D S solid freeform fabrication, ceramic matrix composites, polymer precursor, carbon fibers, silicon oxycarbide

First printing of continuous fibers into ceramics

“…The fiber volume fraction in the samples is about 10.0%. Because the continuous carbon fibers hinder shrinkage, the samples show a small amount of shrinkage. The in‐plane linear shrinkage is only 1.80 ± 0.79% and linear shrinkage in the direction vertical to print plane is 2.73 ± 0.45%.…”

“…Therefore, high‐performance CMCs are difficult to be prepared by these techniques. The slurry‐based 3D printing of ceramic technologies include ink‐jet printing, stereolithography, direct ink writing, etc. These technologies generally prepare ceramic particles or ceramic precursors into liquid or semi‐liquid systems (inks or pastes) as feedstock.…”

“…The complex structures are formed by inkjet printing, photopolymerisation or extrusion and then subjected to de‐binding and sintering at high temperature to obtain ceramics. Franchin et al prepared inks based on preceramic polymers, SiC fillers, and chopped carbon fibers for direct ink writing. CMC components with complex structures can be effectively printed by the inks and relatively excellent mechanical properties can be obtained due to the reinforcement of chopped fibers.…”

Stereolithography of SiOC Polymer‐Derived Ceramics Filled with SiC Micronwhiskers

“…The addition of SiC particles into polymer derived ceramics has been shown to mitigate both mass and shrinkage in addition to aiding to reduce cracking . Therefore, 3D printing a polymer‐derived ceramic reinforced with SiC whiskers was investigated.…”

“…Recently, a handful of emerging studies have explored the use of polymer‐derived ceramics (PDCs) in conjunction with stereolithography . PDCs are a class of ceramics which have been pyrolyzed from a pre‐ceramic polymer at high temperature (e.g., see recent reviews,).…”