Problem definition and objectives: Parallel strand lumber (PSL) beams possess high strength and stiffness in the longitudinal direction due to the proper orientation of strands and high density, making them slightly heavier than solid and laminated wood, while also providing a high load-bearing capacity. Nowadays, to protect forest resources in Iran, the use of fast-growing, planted species such as Eucalyptus camaldulensis, along with wooden waste, has gained special importance for the production of PSL beams. This approach results in a product that is more affordable and cost-effective compared to other engineered wood products. Given the application of PSL beams in wooden structures as beams and columns, there is potential for strengthening and repairing them using fiber-reinforced polymer (FRP) materials. FRPs have gained widespread use in the construction industry due to their advantageous properties, including economic feasibility, high durability, lightweight nature, and resistance to corrosion and impact. This study aims to explore the feasibility of manufacturing PSL beams from Eucalyptus camaldulensis and to enhance their physical and mechanical properties using fiber-reinforced polymer materials.
Methodology: In this research, strands with dimensions of 50 mm in length, 20 mm in width, and two thicknesses of 4 mm and 6 mm were used, mixed with a urea-formaldehyde and melamine-formaldehyde adhesive in a ratio of 70 to 30. To reinforce the boards, four surface treatments were employed with three repetitions each: GFRP with epoxy adhesive, GFRP with polyurethane adhesive, fiberglass orthopedic tape with epoxy adhesive, and gypsum orthopedic band with urea-formaldehyde adhesive. The physical properties measured included water absorption and thickness swelling after 2 and 24 hours of immersion in water, as well as mechanical properties such as static bending (modulus of rupture and modulus of elasticity).
Results: In this study, increasing the strand thickness from 4 mm to 6 mm resulted in an improvement in the mechanical properties (modulus of rupture and modulus of elasticity) of the samples. The independent effect of chip thickness on water absorption after 2 hours and thickness swelling at both 2 and 24 hours was not significant; however, a reduction was observed in the 24-hour water absorption. After reinforcing the boards, the samples treated with fiberglass and epoxy adhesive showed the greatest enhancement in physical and mechanical properties. The water absorption and thickness swelling in the samples reinforced with the gypsum orthopedic band were higher than those in the other samples. The highest mechanical properties were found in the GFRP samples with epoxy adhesive, while the lowest values were recorded in the control samples.
Conclusion: The results indicated that it is feasible to produce parallel strand lumber (PSL) beams from Eucalyptus wood. The reinforcement of PSL beams with GFRP enhanced their mechanical properties, making them suitable for applications subjected to higher loads. Additionally, the reinforcement of the boards with GFRP and epoxy adhesive resulted in reduced water absorption and thickness swelling of the beams, which enhances their applicability in outdoor environments.