Improvement of mechanical properties of oak-wood by bi-directional laminations – Efficacy of standard and pre-stressed glass fibre implants

• Published in: Composite structures 2023-01, Vol.304, p.116465, Article 116465
• Main Authors: Novosel, Andrija, Sedlar, Tomislav, Čizmar, Dean, Turkulin, Hrvoje, Živković, Vjekoslav
• Format: Article
• Language: English
• Subjects: Ductility; Effective stiffness; Glass-fibres (GFRP); Laminated oak-wood; Mechanical properties
• ISSN: 0263-8223; 1879-1085
• DOI: 10.1016/j.compstruct.2022.116465

•Increase in ultimate load up to 55 %.•Effective stiffness increased up to 51 %.•Optimum strength increase is obtained with pre-stressed implants.•Reinforcing with GFRP resulted in an up to 32 % increase in ductility. This paper brings results of the bending testing of oak-wood laminated elements for structural use. The bi-directional laminations were reinforced with six types of implants made of glass fibre reinforced polymer (GFRP), some of which were pre-stressed before embedding in epoxy resin. Previously we reported on improving the mechanical properties of oak-wood laminated elements using carbon fibre implants (CFRP). Although it proved as an efficient improvement of the mechanical properties, it also raised the question of the cost effect to the final product. Therefore, within the larger study on investigating effects of different reinforcement systems, we tested glass fibres reinforced polymer (GFRP) as an alternative. Results showed that the introduction of implants improved the effective stiffness between 4 and 51 % and the ultimate load to failure up to 55 %. Furthermore, not only that insertion of the GFRP layers significantly contributed to the strength and stiffness improvement, but the ductility of the elements increased up to 32 %. Pre-stressing of the glass fibres reinforced polymer implants in tension before their installation contributed to the strength increase to a much greater extent than the increase in the number of layers. The best reinforcement effect is obtained if two layers of pre-stressed GFRP are used.