Evaluation of Mechanical Properties of Engineered Transparent Wood from Several Domestic Hardwood Species

Document Type : Complete scientific research article

Authors

1 . Corresponding Author, Assistant Prof., Dept. of Wood Science and Technology, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran

2 M.Sc. Student of Wood Science and Technology, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran

3 Assistant Prof., Dept. of Wood Science and Technology, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran

Abstract

Background and Objective: In addition to their cost-effectiveness, the primary reason for using polymers in industry and structural applications is their desirable mechanical properties. Consequently, mechanical properties are often of greater importance than chemical and physical properties in most applications and receive significant attention. Therefore, it is essential to gain comprehensive knowledge about these properties and explore ways to enhance mechanical behavior using the structural versatility of polymers. Wood, one of the oldest construction materials, is highly valued in building structures, particularly green structures, due to its lightweight nature and high tensile strength along the fiber direction. The combination of wood’s favorable mechanical properties with various polymers has long been of interest to researchers. Various wood composites are products of this approach. Transparent wood composites, known as transparent wood in the European and American industries, are emerging composites used as substitutes for glass. Investigating the diverse properties of these products is deemed essential to develop commercially viable products.
Materials and Methods: In the present study, three commonly used native wood species in Iran—beech, maple, and poplar—were used to produce transparent wood composites after delignification. Delignification of wood veneers was performed using sodium chlorite (NaClO₂) at a pH of 4.6. The delignified samples were impregnated with epoxy resin (E) and polyvinyl alcohol (PVA) under vacuum conditions. Polymerization of PVA resin was conducted at 40°C in an oven, while epoxy resin was polymerized at ambient temperature. The prepared specimens were evaluated for transparency and then prepared for tensile testing along the fiber direction. Data were analyzed using analysis of variance (ANOVA). Mean comparisons were performed using Duncan’s Multiple Range Test (DMRT) at a 95% confidence level. All statistical analyses were conducted using SPSS software.
Results: The results showed that, despite the delignification process, the veneers retained desirable tensile strength along the fiber direction. Transparent maple wood specimens exhibited favorable properties with both resin types. The properties of products made with PVA resin were superior to those made with epoxy resin. Control specimens of epoxy and PVA polymers exhibited higher strain at break compared to transparent wood composites and other control specimens. Transparent maple wood with PVA resin outperformed other species in terms of ultimate tensile stress and corresponding strain in the longitudinal direction.
Conclusion: Based on the results of this study, the suitable transparency of the produced products, combined with their favorable mechanical properties, makes them suitable for use in structural components where transparent products are subjected to tensile stresses along the fiber direction. The results indicated that both polymer matrices performed acceptably under axial stress, and the high strain of the products further supports this finding.

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References

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Journal of Wood and Forest Science and Technology
Volume 32, Issue 2
June 2025
Pages 85-102

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