A screw extrusion-based system for additive manufacturing of wood: Sodium silicate thermoset composites

The aims of this work were to investigate the printability of high-fraction wood and sodium-silicate composites (WSSC) for additive manufacturing and to develop a screw extrusion-based process to demonstrate this approach for building construction applications. A custom additive manufacturing system was fabricated, and mixtures of 40%-60% wood fiber and 60%-40% sodium silicate were printed. The printability of these formulations was determined by observing their viscosity, extrudability, print-bed and layer adhesion, and curing characteristics. Fiber to resin ratios of 45:55 to 50:50 were the most suitable for printing. The printability was also affected by printing temperature and nozzle travel speed. The mechanical properties of printed and cured WSSC, were determined by three-point bending, tensile, and compression testing. Tensile strength, bending strength, and elastic modulus were found to be comparable to those of 3D printed concrete and other wood-plastic composites reported in the literature. The WSSC was successfully printed into a panel indicating promise for use in additive manufacturing.