Investigation of the repair method alternatives for porous pet structures
Keywords:sandwich composite, porous PET, repair method, wind turbine blade
Wind turbine systems, which are one of the renewable energy sources, convert wind energy into electrical energy, cover the blade components those are produced as sandwich composite materials for the last half century. TPI Composite, a wind turbine blade manufacturer in the renewable energy sector, has an important position in the field.
In the sandwich composite structures, the core material providing the force transfer between the face sheets and plays an important role in increasing the bending stiffness of the sandwich structure. This non-structural material component, which is thicker but lightweight, porous and low density, is used in the wind turbine blade subcomponents.
The main shear web (MSW), which is a subcomponent of the wind turbine composite blade and provides the mechanical strength between the two skins (suction side & pressure side) of the blade, is a composite structure with a parabolic geometric distribution produced by vacuum infusion method. Due to the geometrical shape and placement of various shaped cores of the MSW, there might occur some gaps between the foam cores placed in the MSW during the production due to vacuum. In this study, compression and bending behaviors of the foam core were investigated. Specimens with dimensions of 50x50x30 mm were prepared vacuum infusion method of core structures whose top and bottom skins covered with glass-reinforced epoxy composite face sheets. Then, some specimens were filled with core powder and core strip respectively to represent the repair method. The test specimens were subjected to flatwise compression and three-point bending tests. The performances of different gap filling repair methods were compared, and the changing performance of the damaged core specimens were investigated against specimens without any defect. To evaluate the alternative repair methods that could be applied during the production of MSW, gap filling repair alternatives, repair applicability limits and changing of the mechanical properties compared to virgin specimens were investigated for the sandwich structures with E-glass reinforced/epoxy face sheets and PET foam core.