Effects of defects in composite wind turbine blades – Part 3: A framework for treating defects as uncertainty variables for blade analysis

Abstract

Abstract. Given that wind turbine blades are large structures, the use of low-cost composite manufacturing processes and materials has been necessary for the industry to be cost competitive. Since these manufacturing methods can lead to the inclusion of unwanted defects, potentially reducing blade life, the Blade Reliability Collaborative tasked the Montana State University Composites Group with assessing the effects of these defects. Utilizing the results of characterization and mechanical testing studies, probabilistic models were developed to assess the reliability of a wind blade with known defects. As such, defects were found to be best assessed as design parameters in a parametric probabilistic analysis allowing for establishment of a consistent framework to validate categorization and analysis. Monte Carlo simulations were found to adequately describe the probability of failure of composite blades with included defects. By treating defects as random variables, the approaches utilized indicate the level of conservation used in blade design may be reduced when considering fatigue. In turn, safety factors may be reduced as some of the uncertainty surrounding blade failure is reduced when analyzed with application specific data. Overall, the results indicate that characterization of defects and reduction of design uncertainty is possible for wind turbine blades.

Root Causes and Mechanisms of Failure of Wind Turbine Blades: Overview

“…Generally, manufacturing defects are formed in random locations and their formation is a random event. Riddle and colleagues [102] proposed probabilistic models to assess the reliability of a wind blade with known defects. Considering defects as random variables and design parameters in a parametric probabilistic analysis, the authors demonstrated that safety factors may be reduced, thanks also to a reduced uncertainty of the blade failure.…”

Study on the Effect of Different Delamination Defects on Buckling Behavior of Spar Cap in Wind Turbine Blade

“…In engineering applications, it is found that the delamination defects of UDL (unidirectional laminate) generated in manufacturing or transportation will reduce the strength of the spar cap. Material defects lead to premature failure of blades when subjected to the identified load in static tests or fatigue tests [6][7][8][9][10][11][12][13][14]. Some studies present that delamination and other defects caused by stress will significantly reduce the blade's global performance, especially the buckling at the trailing edge [15][16][17].…”