Effects of defects in composite wind turbine blades – Part 1: Characterization and mechanical testing

Abstract

Abstract. The Montana State University Composite Material Technologies ResearchGroup performed a study to ascertain the effects of defects that often result from the manufacture of composite wind turbine blades. The first step in this multiyear study was to systematically quantify and enter these defects into a database before embedding similar defects into manufactured coupons. Through the Sandia National Laboratories Blade Reliability Collaborative (BRC), it was determined that key defects to investigate were fiber waves and porosity. An inspection of failed commercial-scale wind turbine blades yielded metrics that utilized specific parameters to physically characterize a defect. Methods to easily and consistently discretize, measure, and assess these defects based on the identified parameters were established to allow for statistical analysis. Data relating flaw parameters to frequencies of occurrence were analyzed and found to fit within standard distributions. Additionally, mechanical testing of coupons with flaws based on these physical characterization data was performed to understand effects of these defects. Representative blade materials and manufacturing methods were utilized and both material properties and damage progression were measured. It was observed that flaw parameters directly affected the mechanical response. While the data gathered in this first step are widely useful, it was also intended for use as a foundation for the rest of the study, to perform probabilistic analysis and comparative analysis of progressive damage models.

Radar-derived precipitation climatology for wind turbine blade leading edge erosion

“…This work suggests the dominance of hail as a damage vector for WT blades at all of the sites studied here. This is consistent with indications that deep convection and hail are particularly common in the central US (Cintineo et al, 2012) and indications of large geographic variability in hail frequency (Ni et al, 2017). This finding emphasizes the key importance of efforts to build and enhance hail climatologies Gagne et al, 2019) with applications in a wide range of industries (from insurance to renewable energy).…”

“…The actual likelihood of excess WT LEE and blade damage in any environment is not only a function of the precipitation and wind climate but also of the WT dimensions, materials used in the blade coatings and the coating thickness (Eisenberg et al, 2018;Slot et al, 2015), the presence of existing microstructural defects (Evans et al, 1980) due to manufacturing defects and damage during transportation (Keegan et al, 2013;Nelson et al, 2017), and other aspects of the operating environment (including thermal fatigue and the occurrence of icing; Slot et al, 2015).…”

Investigation of the effect of wrinkle features on wind turbine blade sub-structure strength

“…In some cases wrinkles affect the surface plies causing a bulge [16][17][18][19][20] and in other cases the wrinkle is constrained within the laminate [4,21,22], in which the latter is similar to the current study. A few works dealing with wrinkles are described below where the wrinkle configurations are similar to the configurations in this work meaning wrinkles constrained in the laminate.…”

“…A few works dealing with wrinkles are described below where the wrinkle configurations are similar to the configurations in this work meaning wrinkles constrained in the laminate. In [22] a Glass Fibre Reinforced Polymer (GFRP) plate was manufactured with a wrinkle of 12 • through the entire thickness. The resulting tensile strength reduction was ≈22%.…”

Parametric study of the effect of wrinkle features on the strength of a tapered wind turbine blade sub-structure

“…The face sheets constituted of primarily unidirectional (UD) layers and the primary failure mode was delamination. In [6] a reduction in tensile strength of ≈22% was reported for a maximum wrinkle angle of 12 • for a pure 0 • lay-up. The wrinkle affected all layers and the primary failure mode was delamination.…”