On-Site Gluing and Weather Effects on Tall Wooden Wind Turbine Towers

Abstract

Modvion develops modular wind turbine towers made of wood. The application requires strong and stiff connections and to achieve the desired performance, a hybrid connection with perforated steel plates slotted into LVL modules is used. The parts will be glued together on site, using a polyurethane adhesive (PUR), providing high strength and stiffness to the connection. This paper presents a preliminary screening on how temperature and relative humidity of the surrounding air during assembly and curing will influence the strength of the bond glued on-site. Static tests were performed on the hybrid connections which were glued and cured in different climates. Tests were also performed at different hardening times to evaluate strength growth in the studied climates. The test results show that at cold temperatures of 9 °C to 12 °C there is a breakpoint where the rate of strength growth starts to decline. The experiments show also that the relative humidity may influence the final strength of the bond. However, the low number of tested specimens brings uncertainties to this observation. High temperatures up to 27 ºC and dry climates down to 20% RH did not impact the strength of the tested hybrid connections.