Compression strength reductions in composite laminates due to multiple-layer waviness

Adams, Daniel O.; Bell, Steven

doi:10.1016/0266-3538(95)00020-8

Cited by 56 publications

(37 citation statements)

References 6 publications

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“…3). While previous studies have used aspect ratio or wave severity (amplitude / wavelength) instead of fiber angle as a metric for characterization, such quantification may be slightly more challenging in the field since the aspect ratio requires knowing both the amplitude and wavelength (Adams and Hyer, 1993;Adams and Bell, 1995;Mandell et al, 2003). Even though it is possible that only the fiber angle can be measured directly in the field, wave amplitude (A), wavelength (λ), and off-axis fiber angle (θ) were characterized, as shown in Fig.…”

Section: Wind Industry Blade Survey and Flaw Characterizationmentioning

confidence: 99%

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

Nelson

Riddle²,

Cairns

2017

Wind Energ. Sci.

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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.

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Section: Wind Industry Blade Survey and Flaw Characterizationmentioning

confidence: 99%

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

Nelson

Riddle²,

Cairns

2017

Wind Energ. Sci.

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“…For instance, the reported reductions for Sglass/epoxy composites reach as much as 50 % in compression stiffness, 70 % in compressive strength for a wrinkle severity of d/k = 0.2, while even higher reductions of around 80 % are reported for both compression stiffness and strength of carbon/ epoxy composites with wrinkle severity of d/k = 0.2 (Hsiao and Daniel, 1996). Similarly, Adams and Bell (1995) reported the at fiber undulation in multi-directional laminate caused a 36 % reduction in compressive strength. Adams and Hyer (1994) reported 15 year loss of compression fatigue life for d/k ratios between 0.05 and 0.06 compared to wrinkle-free composites.…”

Section: Adverse Effects Of Fiber Undulation On Mechanical Propertiesmentioning

confidence: 95%

Process Induced Defects in Liquid Molding Processes of Composites

Hamidi

Altan

2017

International Polymer Processing

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Liquid Composite Molding (LCM) processes are cost efficient manufacturing alternatives to traditional autoclave technology for producing near-net shape structural composite parts. However, process induced defects often limit wider usage of LCM in structural applications. Thorough knowledge of these defects, as well as their formation mechanisms and prevention techniques, is essential in developing improved LCM processes. In this article, process induced defects in liquid molding processes of composites, categorized into preform, flow induced and cure induced defects, are reviewed. Preform defects are further presented as fiber misalignment and fiber undulation (waviness and wrinkling). The respective causes, detrimental effects, and possible prevention methods of these defects are presented. Thereafter, flow induced defects are classified as voids and dry spots. Dry spot formation mechanisms in LCM processes and available prevention techniques are summarized. In addition, void formation mechanisms, adverse effects on composite properties, and removal techniques are presented. Cure induced defects include microcracks, void growth and geometrical distortions (warpage and spring-in). Each of these defects are discussed along with their underlying causes as well as their control and reduction schemes.

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“…Several studies have focused on the effect of these wave defects on the compressive strength of the blades [5][6][7][8]. These studies have shown a reduction in compressive strength because the fibers are put into a geometry which increases the potential for a buckling mode of failure in the region of the defect.…”

Section: Figurementioning

confidence: 99%

Simulation of the Manufacturing of Non-Crimp Fabric-Reinforced Composite Wind Turbine Blades to Predict the Formation of Wave Defects

Fetfatsidis¹,

Sherwood²

2011

AIP Conference Proceedings

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NCFs (Non-Crimp Fabrics) are commonly used in the design of wind turbine blades and other complex systems due to their ability to conform to complex shapes without the wrinkling that is typically experienced with woven fabrics or prepreg tapes. In the current research, a form of vacuum assisted resin transfer molding known as SCRIMP® is used to manufacture wind turbine blades. Often, during the compacting of the fabric layers by the vacuum pressure, several plies may bunch together out-of-plane and form wave defects. When the resin is infused, the areas beneath the waves become resin rich and can compromise the structural integrity of the blade. A reliable simulation tool is valuable to help predict where waves and other defects may appear as a result of the manufacturing process. Forming simulations often focus on the in-plane shearing and tensile behavior of fabrics and do not necessarily consider the bending stiffness of the fabrics, which is important to predict the formation of wrinkles and/or waves. This study incorporates experimentally determined in-plane shearing, tensile, and bending stiffness information of NCFs into a finite element model (ABAQUS/Explicit) of a 9-meter wind turbine blade to investigate the mechanical behaviors that can lead to the formation of waves as a result of the manufacturing process.

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Compression strength reductions in composite laminates due to multiple-layer waviness

Cited by 56 publications

References 6 publications

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

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

Process Induced Defects in Liquid Molding Processes of Composites

Simulation of the Manufacturing of Non-Crimp Fabric-Reinforced Composite Wind Turbine Blades to Predict the Formation of Wave Defects

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