Bladena tests blade with combined loading which confirms that D-Stiffener™ avoids cracks on the trailing edge panels
As the awareness about blade failures caused by combined loads increases, the need for changing blade design standards and certification has become a very discussed topic. As part of the EUDP RATZ project, Bladena did a full-scale test with combined loading at BLAEST on a 34m blade. Also, the structural impact of Bladena’s D-Stiffener™ was tested and the expected increase in buckling capacity of the trailing edge area was demonstrated.
Full-scale test with combined loading
The test was loaded with a combined edge and flapwise loading. The load was selected with the angle that gives higher loads. The load was applied at four radial positions of the blade.
The classical way of applying loads in a full-scale blade is by load clamps. Using clamps will restrict the blade to deform and thus prevent it to get the failure modes to evaluate if they occur during the test.
A full-scale test with combined static loads was performed at the certified blade test center BLAEST as part of the EUDP project called RATZ. Measurements in the trailing edge of a 34 meter blade were taken to capture bending/buckling of the trailing edge panels. The load applied was a combination of flap and edgewise loading, which is known to be a more critical load than the traditional pure flap and edge.
The implementation of the tests was proven to not be very demanding making it possible to implement in a short period of time.
Strain measurements showed a clear effect of the D-Stiffeners™. Based on these measurements it was concluded that the actual blade, which showed buckling at a load level at 48%, had no buckling with the D-Stiffeners™ installed when the test was stopped at approximate 60% loading.