Design and manufacturing optimization of epoxy-based adhesive specimens for multiaxial tests

Specimen design and manufacturing quality are decisive factors in the experimental determination of material properties, because they can only be reliably determined if all undesired influences have been minimized or are precisely known. The manufacture of specimens from highly viscous, two-component and fiber-reinforced structural adhesives presents a challenge from this point of view. Therefore, a design and manufacturing optimization procedure for fiber-reinforced structural adhesives and multiaxial testing was developed. It incorporated a finite element parametric study to minimize stress concentrations in the specimen geometry. Vacuum speed mixing was combined with 3D printed mold inserts to enable the manufacture of homogeneous specimens with negligible porosity. The method was demonstrated by means of a structural adhesive used to manufacture wind turbine rotor blades, while the manufacturing quality was verified with high-resolution X-ray microscopy (μCT scanning), enabling detailed detection of pores and geometrical imperfections. The results of uniaxial and biaxial static tests show maximized strength and stiffness properties, while the scatter was minimized in comparison to that stated in international literature. A comparison of the mechanical properties and associated manufacturing techniques is given. The comparison includes a porosity analysis of a specimen from an industrial dosing machine used for rotor blade manufacture. © 2021 The Author(s

Active and Passive Methods for Load alleviation in Wind Turbines

Introduction and Motivation •Increasing wind turbine size •Increasing blade mass •Increasing blade root loads •Further blade increase limited by loads Introduction Sources of loads •Blade mass induced loads (1 perrevolution) •Wind velocity profile •Wind speed varies with position •Wind speed distribution varies periodically (1 per revolution) •Gusts & Turbulences •Local changes of angle of attac

SELECTED RESULTS ON THE DEVELOPMENT AND TESTING OF SMART BLADES TECHNOLOGIES FOR WIND TURBINES

Within the frame of the Smart Blades and the SmartBlades2 projects, different technologies for developing smart rotor blades for wind turbines have been developed and are still being studied and tested. These cover the three following technologies: bend-twist coupled rotor blades; rotor blades with trailing edge flaps and rotor blades with leading edge slats. In addition, cross-technology topics that need to be considered for successfully implementing all three technologies as well as for evaluating their performance within a wind turbine system are being studied