Innovative Effects on GFRP Inserted Epoxy Adhesives with Different Thicknesses for Bonding in Two-Part Wind Turbine Blades

Abstract

Adhesion of hybrid composite materials is essential in the manufacture of wind turbine blades. In the case of huge composite structures, however, the adhesive section between hybrid composite (GFRP, CFRP) was too thick, and it could be lead to decrease adhesion peroperty. In this research, adhesive properties were investigated with different adhesive thicknesses for glass fiber and carbon fiber reinforced hybrid composites. As the adhesive thickness increased, the lap shear strength (LSS) decreased in a rather exponential function. In addition, there were problems that as the thickness of the adhesive increases, voids easily formed inside the adhesive, and the thick adhesive layer had low resistance to bending. Even when the thick bonding section was formed with GFRP addition, added GFRP was deformed more in the bonding part upon the applied external stress. This could be because the interfacial stress was greater than that of the neat epoxy adhesive. It was monitored by 3D electrical resistance (ER) mapping of the CFRP substrate was used to evaluate the shear stress transfer of the bonding part and the CFRP substrate. The addition of GFRP to the epoxy adhesive can improve the adhesion and the resistance to shear failure for thick adhesive parts, such as wind turbine blades (WTB).