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Special Issue "Composites for Wind Energy Applications"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 31 December 2017

Special Issue Editors

Guest Editor
Prof. Bent F. Sørensen

Department of Wind Energy, Technical University of Denmark, Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark
Website | E-Mail
Interests: composites; wind energy; fracture mechanics; materials testing
Guest Editor
Dr. habil. Leon Mishnaevsky Jr.

Senior researcher, Department of Wind Energy, Technical University of Denmark, Risø Campus, Frederiksborgvej 399, 4000 Roskilde, Denmark
Website | E-Mail
Interests: micromechancs; computational materials science; nanocomposites; composites

Special Issue Information

Dear Colleagues,

The drastic expansion of the renewable energy sector is an important precondition for reducing fossil fuel dependency and preventing global warming. Europe seeks to achieve 20% electricity supply from renewable sources by 2020, increasing offshore wind energy capacity by 21% annually. Such an increase in wind energy generation can be realized practically by installing parks from large and extra-large wind turbines off-shore.

The requirements for wind turbine materials are very strict, far stricter than those for automotive and aerospace materials. While a car can be easily repaired at the nearest service station, and airplane materials can be rather expensive, a wind turbine must be cheap (to ensure competitiveness against common energy sources) and sustain 20 or more years of work without failure (due to the very high costs of offshore repair). Due to such extremal requirements, the development of wind turbine materials represents the forefront of composite development.

Wind turbine blades should sustain a combination of extreme mechanical and cyclic multiaxial loading of variable amplitudes, with environmental and thermal/high humidity/erosion effects. This leads to unexpected failures, with resulting downtimes, loss of revenue, increased operational and maintenance costs, with view of the decreased accessibility of off-shore parks.

Currently, most widely-used composites for wind turbine blades are glass fiber/epoxy composites, while investigations using carbon, aramid and basalt fibers, thermoplastics polymers, and bio-based and nanoengineered materials are under way, and also have the potential of yielding practical applications in the long run.

In this Special Issue, recent works and state-of-the-art overviews on the development, modelling, properties, and manufacturing of composites for wind turbines are presented.

We invite prospective authors to submit their manuscripts for this Special Issue. Full papers, communications, and reviews are all welcome.

Prof. Bent F. Sørensen
Dr. habil. Leon Mishnaevsky Jr.
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Wind energy
  • Composites
  • Manufacturing technology
  • Strength and fracture
  • Reliability

Published Papers (3 papers)

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Research

Open AccessFeature PaperArticle Process Modeling of Composite Materials for Wind-Turbine Rotor Blades: Experiments and Numerical Modeling
Materials 2017, 10(10), 1157; doi:10.3390/ma10101157
Received: 31 August 2017 / Revised: 29 September 2017 / Accepted: 1 October 2017 / Published: 5 October 2017
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Abstract
The production of rotor blades for wind turbines is still a predominantly manual process. Process simulation is an adequate way of improving blade quality without a significant increase in production costs. This paper introduces a module for tolerance simulation for rotor-blade production processes.
[...] Read more.
The production of rotor blades for wind turbines is still a predominantly manual process. Process simulation is an adequate way of improving blade quality without a significant increase in production costs. This paper introduces a module for tolerance simulation for rotor-blade production processes. The investigation focuses on the simulation of temperature distribution for one-sided, self-heated tooling and thick laminates. Experimental data from rotor-blade production and down-scaled laboratory tests are presented. Based on influencing factors that are identified, a physical model is created and implemented as a simulation. This provides an opportunity to simulate temperature and cure-degree distribution for two-dimensional cross sections. The aim of this simulation is to support production processes. Hence, it is modelled as an in situ simulation with direct input of temperature data and real-time capability. A monolithic part of the rotor blade, the main girder, is used as an example for presenting the results. Full article
(This article belongs to the Special Issue Composites for Wind Energy Applications)
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Open AccessArticle Full-Scale Fatigue Testing of a Wind Turbine Blade in Flapwise Direction and Examining the Effect of Crack Propagation on the Blade Performance
Materials 2017, 10(10), 1152; doi:10.3390/ma10101152
Received: 8 August 2017 / Revised: 22 September 2017 / Accepted: 29 September 2017 / Published: 3 October 2017
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Abstract
In this paper, the sensitivity of the structural integrity of wind turbine blades to debonding of the shear web from the spar cap was investigated. In this regard, modal analysis, static and fatigue testing were performed on a 45.7 m blade for three
[...] Read more.
In this paper, the sensitivity of the structural integrity of wind turbine blades to debonding of the shear web from the spar cap was investigated. In this regard, modal analysis, static and fatigue testing were performed on a 45.7 m blade for three states of the blade: (i) as received blade (ii) when a crack of 200 mm was introduced between the web and the spar cap and (iii) when the crack was extended to 1000 mm. Calibration pull-tests for all three states of the blade were performed to obtain the strain-bending moment relationship of the blade according to the estimated target bending moment (BM) which the blade is expected to experience in its service life. The resultant data was used to apply appropriate load in the fatigue tests. The blade natural frequencies in flapwise and edgewise directions over a range of frequency domain were found by modal testing for all three states of the blade. The blade first natural frequency for each state was used for the flapwise fatigue tests. These were performed in accordance with technical specification IEC TS 61400-23. The fatigue results showed that, for a 200 mm crack between the web and spar cap at 9 m from the blade root, the crack did not propagate at 50% of the target BM up to 62,110 cycles. However, when the load was increased to 70% of target BM, some damages were detected on the pressure side of the blade. When the 200 mm crack was extended to 1000 mm, the crack began to propagate when the applied load exceeded 100% of target BM and the blade experienced delaminations, adhesive joint failure, compression failure and sandwich core failure. Full article
(This article belongs to the Special Issue Composites for Wind Energy Applications)
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Open AccessFeature PaperArticle On the Material Characterisation of Wind Turbine Blade Coatings: The Effect of Interphase Coating–Laminate Adhesion on Rain Erosion Performance
Materials 2017, 10(10), 1146; doi:10.3390/ma10101146
Received: 31 August 2017 / Revised: 21 September 2017 / Accepted: 22 September 2017 / Published: 28 September 2017
PDF Full-text (24115 KB) | HTML Full-text | XML Full-text
Abstract
Rain erosion damage, caused by repeated droplet impact on wind turbine blades, is a major cause for concern, even more so at offshore locations with larger blades and higher tip speeds. Due to the negative economic influence of blade erosion, all wind turbine
[...] Read more.
Rain erosion damage, caused by repeated droplet impact on wind turbine blades, is a major cause for concern, even more so at offshore locations with larger blades and higher tip speeds. Due to the negative economic influence of blade erosion, all wind turbine Original Equipment Manufacturers (OEMs) are actively seeking solutions. In most cases, since the surface coating plays a decisive role in the blade manufacture and overall performance, it has been identified as an area where a solution may be obtained. In this research, two main coating technologies have been considered: In-mould coatings (Gel coating) applied during moulding on the entire blade surface and the post-mould coatings specifically developed for Leading Edge Protection (LEP). The coating adhesion and erosion is affected by the shock waves created by the collapsing water droplets on impact. The stress waves are reflected and transmitted to the laminate substrate, so microstructural discontinuities in coating layers and interfaces play a key role on its degradation and may accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations based on their potential stress reduction on the interface. Nevertheless, in order to use them, it is necessary to measure the contact adhesion resistance of the multi-layered system interfaces. The rain erosion performance is assessed using an accelerated testing technique, whereby the test material is repeatedly impacted at high speed with water droplets in a Whirling Arm Rain Erosion Rig (WARER). The materials, specifically the coating–laminate interphase region and acoustic properties, are further characterised by several laboratory tests, including Differential Scanning Calorimetry (DSC), pull-off testing, peeling–adhesion testing and nanoindentation testing. This body of work includes a number of case studies. The first case study compares two of the main coating technologies used in industry (i.e., gel coating and LEP); the second case investigates the effects of the in-mould gel coating curing; and the third considers the inclusion of a primer layer on a LEP configuration system. Following these case studies, the LEP is found to be a far superior coating due to its appropriate mechanical and acoustic properties and the interface between the coating and the substrate is highlighted as a key aspect, as poor adhesion can lead to delamination and, ultimately, premature failure of the coating. Full article
(This article belongs to the Special Issue Composites for Wind Energy Applications)
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