Effect of print direction on mechanical properties of 3D printed polymer-derived ceramics and their precursors

The use of engineering ceramics with intricate geometries is limited by manufacturing processes and lack ease of machinability of ceramics. Additive manufacturing of pre-ceramic polymers which are pyrolyzed into ceramics after 3D printing has recently been used to circumvent traditional manufacturing processes creating ceramics with complex geometries, however, mechanical characterization is limited. Polymer-derived ceramics and their green-body precursors are printed using digital light projection 3D printing in two orientations (0°- and 90°- to the build plate) and mechanically characterized. The results show that mechanical anisotropy exists both in the green-body polymer samples where the 0°-samples are stronger and stiffer than their 90°-counterparts and the final ceramics, where the stronger samples are fabricated at 90° despite isotropic hardness measurements. Through the manufacturing process, it was noted that samples undergoing pyrolysis built in the 90°-orientation have a pyrolysis survival rate of 94% whereas the 0°-samples showed a survival rate of 54%. The results suggest that the build-direction of 3D printed green-bodies plays a role in both material manufacturing and mechanical integrity of the final ceramic materials.