A continuous-flow processing system for wood-based thermoset composites with applications in 3D construction printing

Abstract In this work, a continuous-flow processing system for high-fraction wood-thermoset composites specialized for additive manufacturing in construction applications was developed. A wood-sodium silicate composite (WSSC) was produced at a 50:50 fiber-to-resin mass ratio, utilizing a novel inline mixing method designed to effectively integrate dry wood flour with aqueous sodium silicate binder under controlled shear conditions. The homogeneity of the resulting WSSC was evaluated through bulk density analysis, near-infrared (NIR) spectroscopy, and micro-CT scanning to ensure consistent material composition throughout the continuous extrusion process. To assess structural performance, dimensional stability and compressive strength were determined to ensure geometric accuracy during deposition and curing and load-bearing capacity, respectively. Compression testing evaluated the influence of the printing process on mechanical integrity by comparing samples of one, two, and five layers to quantify the impact of stacking staking on the ultimate compressive strength of the printed composites. The feasibility of this continuous-flow framework was demonstrated through the successful printing of a large-scale, two-step structural staircase prototype, highlighting the potential for sustainable, bio-based materials to replace traditional concrete in complex structural geometries.