Climate change concerns have spurred research into natural fiber composites (NFCs), which offer advantages over synthetic ones, such as lower environmental impact and cost [1]. The lumber industry generates significant by-products, often thermally processed, leading to CO2 emissions. Utilizing these by-products can reduce the environmental impact and increase the economic value of wood processing. Their retained microstructure (see Figure 1a) makes them valuable for creating high-performance NFCs. Fibers can be obtained through chemical and mechanical pretreatments and optimized for various requirements [4]. Other constituents extracted from the cell wall and bark are later used as binders in the production of biocomposites [3,5], as shown schematically in Figure 1a.
To understand the mechanical behavior of biocomposites, it is crucial to investigate the mechanical properties of the individual phases at various scales. Thus, in this study, we conducted tensile tests on pulp fibers. Since such experiments are highly time-consuming, we are exploring fast analytical multi-scale models to predict the mechanical properties based on the fibers’ chemical and physical composition (see Figure 1b) [6]. Key factors influencing the physical properties of natural fibers include fiber structure, cellulose content, microfibril angle, cross-sectional area, and degree of polymerization [2]. Mechanical properties such as strength and stiffness are scaled up by a two-step homogenization scheme using volume fractions of the cell wall – cellulose, hemicellulose, lignin, pectin, extractives, ash, and pores – as input parameters. Next, the models are expanded to incorporate 2D structures. This facilitates the prediction of the mechanical properties of paper strips impregnated with technical lignin [5] and serves as a foundation for the long-term goal of expanding the models to 3D structures to predict the mechanical properties of biocomposites.