Printing parmeters for 15 wt% wood PLA/PHA(poly(hydroxyalkanoate) 2.85 mm +-0.1mm,
layer height of 3mm, nozzle temp of 210C, heated bed of 70C, and a printing speed of 18mm/s
Wood fibre orientation within the polymer matrix is brought about by the extrusion process leading to anisotrophic properties.
What is the difference between the samples in biochemical composition(type of wood) and thus their microstructures and any adhesive if present.
The greater the porosity induced in the part by the printing parameters(namely the line width), the greater the decrease in tensile strength, up to 50% for 300% increase in line width.
Greater porosity also increases the hygroscopic capabilities of the printed material, i.e. more surface area, also reinforced by the olar nature of wood fibre
The FDM process creates layer to layer bonding only due to the interdiffusion based primarily on temperture, while other manufacturing processes introduce some pressure or shear rate to reduce porosity.
Due to the natural hydrophilic nature of wood fibre, actuation of printed material may be observed when layers perp to the longintudinal direcion are printed. swelling due to water is maximal in the transversely printed layer.
Wood can be self transformed(programmed) using precise humidity concentration control.
Wood is extremely common and still a difficult material to shape and form precisely due to anisotropic and hygroscopic properties. But 3D printing allows those limitations to then become strengths.
The level of moisture in wood may be affteded by local atmospheric changes(temp, rel. humid, radiation) through direct, or indirect wetting.
Wood fibers undergo a shear-induced alignment in the nozzle and some are longitudinally positioned along the extrusion path.
Two main methods used:
printing a smooth layer, then printing a textured layer to induce stress resulting in folding or curling deformations when subjected to specific heat or moisture conditions
printing alternating layers of different wood compositions, or pure polymer to make a multimaterial print, where the material properties of volumetric expansion, bending stiffness, and modulus of elasticity impact layer properties.