Characterization of Manufacturing Defects Common to Composite Wind Turbine Blades: Flaw Characterization

Riddle, Trey; Cairns, Douglas S.; Nelson, Jared

doi:10.2514/6.2011-1758

Cited by 23 publications

(20 citation statements)

References 9 publications

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“…As such, matrix cracking damage was estimated by: (5) where σ 22 and S 22 are transverse stress and transverse strength, respectively and τ 12 and S 12 are shear stress and strength, respectively. It must be noted that this same equation is utilized for both tensile and compressive cases and the associated material properties are changed for each case (Table 1).…”

Section: Table 3 Progressive Damage Outline and Degradation Approachmentioning

confidence: 99%

“…Thus, research specific to understand the criticality of defects common to blades is necessary and coupon level, benchmark testing was performed by the MSUCG. [4][5][6][7][8][9] The prior benchmark material testing (BMT) was performed to establish and understand the material properties, failure points and modes, and damage progression of both unflawed and flawed specimens. For example, it was clearly evident that once a flaw was introduced, the material response in the flawed area dominated the overall response in most cases as indicated by the review of digital image correlation data as seen in Figure 2.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Defects: Part B—A Comparison of Progressive Damage Modeling of Fiberglass/Epoxy Composite Structures with Manufacturing Induced Flaws

Nelson

Cairns

Riddle

2014

32nd ASME Wind Energy Symposium

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Application of different damage modeling approaches for use with composite materials and composite material structures has grown with increasing computational ability. However, assumptions are often made for "worst case" scenarios with these modeling techniques In order to develop a tool that will allow for accurate analysis of a complete structure, modeling approaches must be optimized by including defects of different parameters. It was the optimization of these approaches that was investigated herein with specific application toward establishing a protocol to understand and quantify the effects of defects in composite wind turbine blades. A systematic, three-round study of increasing complexity was performed to understand the effects of three typical blade manufacturing defects while investigating continuum, discrete, and combined damage modeling. Through the three rounds of the benchmark material testing, significant coupon level testing was performed to generalize the effects of these defects. In addition, material properties and responses were analyzed and then utilized as material inputs and correlation criteria for each analytical technique. A standard defect case was initially used for each modeling technique and correlation was compared both qualitatively and quantitatively. While each modeling type offered certain attributes, a combined approach yielded the most accurate analytical/experimental correlation. Thus, a unique comparison of several different analytical approaches to composites with respect to manufacturing for consistency, accuracy, and predictive capability allowing for improved blade reliability and composite structural assessment. NomenclatureBRC = Blade Reliability Collaborative MSUCG = Montana State University Composites Group BMT = Benchmark Material Testing OP = Out-of-plane wave IP = In-plane wave CDM = Continuum Damage Model DDM = Discrete Damage Model UMAT = User Material Subroutine σ = Stress ε = Strain u = Displacement

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Section: Table 3 Progressive Damage Outline and Degradation Approachmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Defects: Part B—A Comparison of Progressive Damage Modeling of Fiberglass/Epoxy Composite Structures with Manufacturing Induced Flaws

Nelson

Cairns

Riddle

2014

32nd ASME Wind Energy Symposium

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“…6 These results were then utilized to build simple analytical models with the purpose of performing laminate analysis with included defects in a coordinated effort with the Flaw Characterization task. 5,7 An understanding of the changes in the material properties associated with characterized flaws was achieved on a coupon level with physical testing being performed with several configurations of each of the different flaw types. This testing clearly indicated that fiber misalignment and porosity resulted in degraded material properties and decreased material performance.…”

Section: Introductionmentioning

confidence: 99%

“…As such, the MSUCG has divided this effort into two distinct tasks: Part A-Flaw Characterization, and Part B-Effects of Defects. [5][6][7][8] The function of the Flaw Characterization effort has been to provide quantitative analysis for two major directives: (1) acquisition and generation of quantitative flaw data for use in the Effects of Defects numerical modeling program; and, (2) development of a flaw severity designation system and probabilistic risk management protocol for as-built flawed structures. The Effects of Defects portion is focused on the development of modeling capabilities to predict the damage progression and structural implications of common flaws found in composite wind turbine blades.…”

Section: Introductionmentioning

confidence: 99%

Effects of Defects: Part B—Progressive Damage Modeling of Fiberglass/Epoxy Composite Structures with Manufacturing Induced Flaws Utilizing Cohesive Zone Elements

Woo

Nelson

Cairns

et al. 2013

54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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The Effects of Defects is important for the reliability of modern composite wind turbine blades. The DOE has sponsored a comprehensive study to characterize common manufacturing defects and establish damage growth and validation tools to contribute to a wind turbine blade reliability infrastructure. To support this development of a reliability infrastructure, progressive damage modeling of blade representative coupons has been performed. A model has been developed that is combined of both continuum and discrete modeling approaches. A user-defined material subroutine has been created and used with material properties established from experimental testing for the former, while cohesive zone elements were placed between each fiber tow to capture the fracture that occurs in these areas for the latter. Two-dimensional (2D), four-layer coupon level models were generated based on the geometry of the as-tested specimens. Results from this model were compared to the visual damage progression and stress-strain data from in-plane wave tests in tension and compression. While the uniformity of the models resulted in more dramatic changes at failure points, the progression was found to match in these cases, thereby verifying the combined continuum and discrete modeling approach. NomenclatureBRC = Blade Reliability Collaborative MSUCG = Montana State University Composites Group OP = out-of-plane wave IP = in-plane wave CDM = Continuum Damage Model DDM = Discrete Damage Model σ = Stress ε = Strain u = displacement

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“…The thickness of the spar cap varies along the blade length; generally, the thickest zone (over almost 50 layers) is always from the maximum chord to 1/2 of the blade length, which is also the most important load-carrying zone of a spar cap. In this thick layer zone, it is easy to produce in-plane wrinkles and out-plane wrinkles during the blade manufacturing, which significantly reduces the local strength of the spar cap [13,14]. Under the alternating action of the ultimate load and fatigue load, the coupling response of delamination and buckling may easily occur in this zone [15][16][17][18][19][20].…”

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confidence: 99%

Experimental Study of Stepped-Lap Scarf Joint Repair for Spar Cap Damage of Wind Turbine Blade in Service

Chen

Wang

et al. 2020

Applied Sciences

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The objective of this paper was to design configuration parameters for a stepped-lap scarf joint repair, which can be used for spar cap damage of a wind turbine blade in service and to realize the post-repair monitoring. Two experimental studies were included. First, tensile test for the unidirectional tape specimens with a large aspect ratio repaired using a multiple stepped-lap scarf joint method was carried out. The results showed that the reinforcement layer could effectively improve the load-carrying capacity of the repaired zone. The stepped-lap joint surface was identified as the weak part of the spar cap repair, which should be monitored. Second, by embedding carbon nanotube buckypaper sensors on the stepped-lap joint surface of the repaired specimens, quasi-static tensile tests and fatigue tests were carried out. According to the resistance response of the sensors, the quasi-static tensile test confirmed the failure processes, namely the stiffness turning point, damage evolution, crack propagation, and fracture. The fatigue test could accurately identify the progressive failure, namely the initial damage, damage accumulation, initial cracking, and crack propagation to structural failure. The above tests provided an important configuration parameter basis for evaluating the spar cap repair scheme and presented a promising method for the health monitoring of a spar cap after repair.

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Characterization of Manufacturing Defects Common to Composite Wind Turbine Blades: Flaw Characterization

Cited by 23 publications

References 9 publications

Effects of Defects: Part B—A Comparison of Progressive Damage Modeling of Fiberglass/Epoxy Composite Structures with Manufacturing Induced Flaws

Effects of Defects: Part B—A Comparison of Progressive Damage Modeling of Fiberglass/Epoxy Composite Structures with Manufacturing Induced Flaws

Effects of Defects: Part B—Progressive Damage Modeling of Fiberglass/Epoxy Composite Structures with Manufacturing Induced Flaws Utilizing Cohesive Zone Elements

Experimental Study of Stepped-Lap Scarf Joint Repair for Spar Cap Damage of Wind Turbine Blade in Service

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