Combined Experimental and Machine Learning Study on the Interplay between Delignification and Mechanical Properties for Improved Poplar Wood Reconstruction

Structure-retaining delignification of wood is widely used to obtain scaffolds suitable for the preparation of high-performance biobased composites. However, this often comes at the expense of sustainability and large-scale production potential. To address these issues, we reconstructed poplar wood via room-temperature partial delignification, followed by delignification and densification. Compared to fully delignified samples, those obtained with partial delignification have superior mechanical properties at 45° and 90° fiber directions with respect to the loading direction, but lower ones at 0°. Working at room temperature facilitated sample up-scaling and allowed reuse of the delignification solution multiple times without compromising product quality. As shown by life cycle assessment (LCA), the possibility of repeatedly reusing the delignification solution led to a significant reduction in the global warming potential (GWP) and ecosystem quality (EQ) impacts. We then developed an 'unsupervised, supervised classification, supervised regression' (USS) learning framework to accurately predict the mechanical properties of reconstructed poplar on the basis of structural and process-related features, followed by feature importance analysis to determine the key parameters influencing material performance. With our approach, we were able to estimate the mechanical performance of the reconstructed samples and gain insight into the most relevant material-fabrication parameters.