Conclusion

This study investigated the mechanical response associated with nominal wood-particle content and post-printing fungal colonisation by Fomes fomentarius in the tensile behaviour of additively manufactured PLA/wood material combinations manufactured by MEX AM. In addition, a screening-level Life Cycle Assessment (LCA) was performed to evaluate environmental impacts associated with the fabrication stage.

The main findings can be summarised as follows:The investigated PLA/wood material combinations exhibited mean Young’s modulus (E) values between 2025.39 and 2685.01 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {N/mm^2}$$\end{document} and mean Ultimate Tensile Strength (UTS) values between 31.88 and 37.98 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mathrm {N/mm^2}$$\end{document}.Because the investigated commercial filaments originated from different manufacturers, differences in mechanical performance cannot be attributed exclusively to nominal wood-particle content and may additionally be influenced by formulation-specific factors such as PLA grade, additives, wood species, particle morphology, and compounding procedures. Across all investigated material combinations, fungal-colonised specimens exhibited lower mechanical performance than their corresponding untreated counterparts. Mean E decreased by approximately 7.1–10.5 %, while mean UTS decreased by approximately 2.2–6.8 %. ANOVA analyses confirmed statistically significant differences between untreated and fungal-colonised specimens.Microscopy images confirmed successful fungal growth on specimen surfaces. However, the present study does not allow direct conclusions regarding the mechanisms responsible for the observed reductions in mean E and mean UTS, highlighting the need for further microstructural investigations.Within the present screening-level assessment, the relative importance of material composition and manufacturing energy depends on the considered impact category. GWP is dominated by electricity consumption during MEX AM fabrication, EP is primarily governed by PLA content, and AP is influenced by both material consumption and electricity demand.

Overall, the combined mechanical and environmental evaluation demonstrates that fungal colonisation can significantly affect the tensile performance of additively manufactured PLA/wood material combinations, while environmental impacts depend on different underlying mechanisms. Consequently, mechanical performance and environmental performance should be considered simultaneously when assessing bio-based additively manufactured composites.

The presented framework combining tensile characterisation, fungal colonisation, microscopy, statistical analysis, and screening-level LCA provides a basis for future investigations of sustainable fungal-mycelium-colonised additively manufactured composite materials.