Representative Hardwood and Softwood Green Tissue-Microstructure Transitions per Age Group and Their Inherent Relationships with Physical–Mechanical Properties and Potential Applications

Abstract

A better understanding of wood form–structure–function relationships and potentialities can lead to an enormous pool of fascinating solutions and inventions. In this research advances from both the anatomical and the mechanical points of view, the principles, fundamentals and concept generators derived from the inherent relationship between green tissue-microstructure and physical–mechanical properties of two representative woody species. Specifically, a total of 120 small-clear samples cut from six (e.g., three per wood species) Eucalyptus globulus (i.e., hardwood) and Cupressus macrocarpa (i.e., softwood) trees were sampled and tested to determine the tissue transitions per age group (e.g., juvenile, mature and senile) in terms of density, area, roundness and sphericity of vessel elements, longitudinal tracheids and longitudinal/ray parenchyma cells. Moreover, the studied green tissue-microstructure transitions were compared and analysed with the corresponding physical–mechanical properties [i.e., green density, moisture content, modulus of rupture (MOR) and modulus of elasticity (MOE)] of each species, which in turn were acquired from 159 tests carried out according to the German Deutsches Institut für Normung (DIN standards). The results herein show mature and senile wood tissues are more rigid and mechanically resistant than juvenile ones, which is partially influenced by the progressive increment in cell-wall thickness as the wood-tissue ages, and this process is of greater magnitude for the eucalyptus species. Indeed, this representative hardwood species was found superior in terms of mechanical resistance to the progression of stresses due to a complex porous vascular system that becomes stronger as the tissue-microstructure ages. The design principles underlying the natural architectures of both studied green tissues provide concept generators for potential biomimetic and engineering applications, e.g., eucalyptus species are suitable for structural applications, whereas the superior flexibility found in the cypress species could be well bio-mimicked into composite panels, where the balance between strength and rigidity is of high relevance.

Tree species-based differences vs. decay performance and mechanical properties following chemical and thermal treatments

“…With no treatments, E. globulus wood had the highest MOE and MOR; it was previously reported as a wood species with high mechanical properties (Majano-Majano et al 2020). In addition, after the leaching test, the MOR and MOE were reduced, which agrees with the findings of previous researchers (Mauricio González et al 2020).…”

A Review on Mechanical Performance of Hybrid Natural Fiber Polymer Composites for Structural Applications

“…Based on plant taxonomy, there are the two main categories of woody species: hardwoods and softwoods. Wood is a biomaterial with an optimal hierarchical system capable of transferring both internal and external forces, making it perfectly suited as a structural material in a variety of applications [ 38 ].…”

A Review on Antimicrobial Packaging from Biodegradable Polymer Composites

“…In particular, metal and metal oxides are potential antibacterial agents, but issues concerning their long-term impact on the environment and human health remain unresolved. On the other hand, the use of silver-based antimicrobial packaging for food purposes is expected to grow and has been used in countries such as Japan and the United States [ 48 ].…”

“…The presence of active compounds in these materials such as flavanols, terpenes, anthocyanins, phenolic acids, tannins, and stilbenes is responsible for the antimicrobial effects for specific microorganisms. Moreover, they could provide additional health benefits such as being nutritional supplements [ 48 ]. From this point of view, the use of antimicrobial agents from plant-derived sources could be an excellent choice especially for food packaging purposes.…”