Computational Micromechanics and Future of Wind Energy Materials: Lecture

Recently, I delivered a presentation titled “Computational Micromechanics of Materials and Optimization of Wind Energy Technologies”. (https://panopto.dtu.dk/Panopto/Pages/Viewer.aspx?id=695b142d-cc5b-4621-968b-b3d8008a7279&start=0 ) The central question was straightforward: how can wind energy technologies be optimized on a solid scientific basis? The answer lies at the microscale. Blade failure is governed by microscale defects; recycling efficiency is controlled by the dissolution and reconfiguration of polymer chains; and microplastic emissions originate from the spalling and fragmentation of microscale polymer particles. In other words, the most critical performance, durability, and sustainability challenges in wind energy are dictated by material-level processes occurring far below the structural scale. Computational materials science provides the quantitative framework needed to analyze these mechanisms and to translate microscale behavior into optimized material design and technology choices. In this presentation, we introduce the core principles of computational micromechanics and demonstrate how they can be applied to the rational optimization of wind energy materials and technologies. 

Technology Intelligence Brief: Anti-erosion coatings for wind turbine blades

Recently, Birgit Junker delivered a special lecture, “What Academics Don’t Know but Should Know About Wind Blades,” at our symposium. On the other hand, there is probably information and knowledge that we academics should share with practitioners — busy professionals who do not always have time to read how we solved differential equations 📐🧑‍🔬. We have decided to explore a new format of technical summaries and assessments: short Technology Intelligence Briefs (TIBs), two-page documents presenting only the main observations on selected topics. Here, we summarize the material-related factors defining the quality of anti-erosion coatings and shells for the leading edges of wind turbine blades. We likely miss some factors — feel free to comment and add. 

New generation of recyclable composites for wind blades: New publication

In 2023, Mingyang launched wind turbine blade made from recyclable materials. Siemens Gamesa developed  wind turbines with RecyclableBlades. Other companies work on other recyclable materials for blades, notably, vitrimers. Indeed, these new materials are recyclable. But how to recycle them in optimal way, to get high quality recycled products - which solvents, which temperature regimes? 

In our new article “Solvolysis of novel recyclable composites for next-generation wind turbine blades”,  we developed an advanced computational model of chemical recycling (solvolysis and depolymerization) for the new generation of composites based on recyclable thermoset polymer matrix.  The model incorporates realistic composite microstructures, including microscale defects such as manufacturing-induced voids, to examine their impact on the end-of-life recycling process, and can be a basis for the optimization of recycling technology. This work is a continuation of our previous works, “Modeling the solvolysis of composite materials of wind turbine blades”,  “Multifield computational model of chemical recycling of polymer composites” and “How to repair the next generation of wind turbine blades” . The works were carried out in the framework of WiseWind project (“WiseWind: NeW generatIon of SustainablE Wind turbine Blades”, https://wisewind.dtu.dk/). 

Nanoreinforced polymers for composite structures and coatings: Overview. 

Link. The performance of composite materials is governed by the properties and interactions of their primary constituents—the matrix and the reinforcements. The key question is whether composite performance can be tuned beyond this classical design space—whether an additional “control parameter” can be introduced to selectively enhance targeted properties. This can be achieved through the incorporation of nanoparticles. Nanoreinforcements enable performance tuning at length scales inaccessible to conventional fibers or fillers. Properly engineered, they can significantly improve fatigue lifetime, durability, and impact resistance of both composites and coatings. Moreover, nanoparticles allow the introduction of new functionalities, such as self-sensing, damage monitoring, or enhanced electrical and thermal properties, without fundamentally altering the composite architecture. Over the last years, we at DTU Wind investigated the potential of nanoreinforced materials for various applications. We collaborated with many teams and colleagues, around the world, including Kaunas University of Technology in Lithuania, Kingston University in UK, China University of Mining and Technologies, CSIR - National Aerospace Laboratories (NAL) and IIT Delhi in India, and many others. 

Technology Intelligence Brief: Robotic repair of wind turbine blades

Following our initiative to prepare short two-page Technology Intelligence Briefs (TIBs), we present here a brief overview of another important topic: robotic repair of wind turbine blades. Maintenance costs of wind turbines — particularly offshore turbines — are high. Blade repair operations typically require teams of highly skilled technicians working for several hours, often using rope-access techniques or service platforms. These operations must be performed within relatively narrow weather window. A lot of things can go wrong. Imagine also the costs. Can one automatize this procedure, send a robot or drone to repair the blade? If one can send robots to Mars, why don’t let them paint a blade? A lot of people had this idea. The area is developing quickly, new ideas and better technologies and solutions come every year. Here, we summarize the current situation with the robotic repair of blades. Again, probably we miss many factors - feel free to comment and to add. 

Ultraviolet curing technology for the repair of composites 

Repair of wind turbine blades is very expensive: Imagine how much it costs to send a ship or helicopter to an offshore wind park, to build a platform, and let several technicians work for 7..8 hours on special platform near offshore wind turbine. But why does it take hours? Repair includes, most often, bonding and solidification of adhesives (e.g., adhesive between repair scarf and damaged blade). Polymer solidification can take several hours. But what if we use quickly curing adhesives, where solidification process is controlled by ultraviolet radiation? Then, the solidification process takes just 20...30 minutes. How strong will be such adhesives, how reliable the repaired blade?  This is the topic of our new publication ”Ultraviolet (UV) curable resin-based repair of wind turbine blades: Perspectives and computational analys”. We investigate how reliable is this technology, which residual stresses and defects can form, and which post-repair behaviour is observed. The work is a part of Danish-Indian project Maintainergy (https://www.maintainergy.dk/) 

Microplastic emission during repair of wind turbine blades

Our new article ”Maintenance of wind turbine blades and microplastic emission: How to mitigate environmental risks” includes the evaluation of emitted microparticles volume, and the effect of maintenance/grinding conditions on the fraction of smallest particles (https://doi.org/10.1002/we.70072 ). Two impottant conclusions: The microplastic emission due to blade maintenance (as well as due to blade erosion) is at the very low level, two orders of magnitude lower than that of car tires, textiles, and paints. And: By using coarse grinding paper, one can reduce the fraction of smallest particles, and therefore, mininimize any possible environmental risks. 

Repair of composite blades of wind turbines: Overview

Repair of composite blades of wind turbines: Why repair of wind turbine blades is so challenging? It should be price competitive (as whole wind energy industry, due to price pressure from other energy sources). It should be almost perfect (while people don't start jogging next day after a heart operation, wind turbines should work under full loading after repair). It is done under challenging conditions (e.g., on rope and offshore). And it is also a complex process of bonding two anisotropic bodies by thermally or radiation assisted polymer solidification. In series of investigations, we explored economy, technology and environmental aspects of wind turbine blades repair. Here, slides of my latest presentation at the Danish-Indian Workshop on Wind Turbine Maintenance Strategies earlier this year. 

Self healing interfaces in composites

Composite structures failure starts most often from interfaces or adhesive joints. Thus, if we suppress interface defects, we can prevent the overall failure of structures, long before it even started. The attractive idea is to initiate self-healing of interface defects. In ideal case, it will lead to permanent prevention of defects at early stages, and (in ideal case) to infinite life time of composite structures (or until next crash/typhoon). How to make the interfaces self-healing? Dr. Yulin Sun, Dr. Laura Simonini, Dr. Xing and I published a new paper “Self-healing interfaces in fiber reinforced polymers “, where we studied the self-healing of composite interfaces. Link: https://doi.org/10.1016/j.compscitech.2025.111269 . 

In our earlier work “Healable polymer blends for structural applications”, Dr. Sun and I also studied self-healing of structural polymer composites, https://doi.org/10.1016/j.ijmecsci.2025.109938 . The mechanisms of self-healing in these two cases are different, and we carrying out investigations now how to combine them. 

Chemical recycling of wind turbine blades

In our new paper “Multifield computational model of chemical recycling of polymer composites: Temperature effects on solvolysis efficiency and energy consumption” (https://doi.org/10.1016/j.jclepro.2025.145313), we proposed a multifield computational model of chemical recycling (solvolysis), that integrates diffusion, chemical reaction, temperature distribution, and mechanical responses. What is the problem? It was demonstrated in many works, that wind turbine blades can be recycled, using solvolysis (and also some other technologies) (https://www.mdpi.com/1996-1944/14/5/1124). The problem is that the depolymerization is still expensive process, and the recycled fibers can come damaged at the end, with reduced strength and residues. In other words, the process is expensive, and the output is of low quality. How to optimize this process? For this, we (Yi, Justine, Asger and I) developed this model. Analyzing the temperature effect, we observed that while higher temperatures reduce the time required for matrix dissolution, they also increase energy consumption and reduce the mechanical strength of recovered fibers. The next step will be to optimize the recycling regimes, using the quantitative model of solvolysis. This computational model can be also expanded for pyrolysis, and other recycling technologies. This model is based on our previous works, ”Modeling the solvolysis of composite materials of wind turbine blades” (https://doi.org/10.1002/adem.202302150) and ”Recycling carbon fibers by solvolysis” (https://doi.org/10.1016/j.compositesa.2024.108667), where we observed the link between the availability of manufacturing defects in compoites and the recycling efficiency, and recycled fiber quality. Summarizing: If we have high quality composite, and recycle it, using  intelligent control  of thermal regime, one can get relatively high quality fibers, with reasonably low costs. Further, with this model, we can comoare different recycling technologies. 27.3.2025

Nanoengineered composites and coatings for multifunctional smart structures

New research publication on nanoengineered coatings for corrosion protection, “Layered double hydroxides reinforced epoxy composites” (https://doi.org/10.1016/j.commatsci.2025.113816 ), our long term collaboration with Kaunas University of Technology, Sigitas Kilikevičius and Professor Daiva Zeleniakiene. In this article, the effect of nanoparticle reinforcements on the strength of polymer nanocomposites is explored. This article continues the series of investigationss on the effect of various nanoreinforcements (carbon, graphene, Mxenes) on the properties of composites, and possibility to add additional functionalities to the composites (like self-sensing, explored in our recent publication by Daiva Zeleniakiene, Gediminas Monastyreckis and Gabrielė Jovarauskaitė , ”Self-sensing composites with damage mapping using 3D carbon fibre grid”, https://doi.org/10.1016/j.compositesb.2025.112182). In the earlier works, hybrid polymer composites with graphene and Mxene nanoreinforcements (https://doi.org/10.3390/polym13071013) and MXene-polymer composites (https://doi.org/10.1016/j.carbon.2020.02.070 ) were studied. In our even earlier project, we studied and tested, carbon fiber/carbon nanotube based hierarchical composites (https://doi.org/10.1016/j.compositesb.2015.10.035) and graphene/polymer interfaces (https://doi.org/10.1016/j.commatsci.2014.08.011). There is huge potential in nanoengineering of composite materials, to develop new generations of multifunctional smart materials and structures. 20.3.2025

Self-healing wind turbine blades - is it possible?  

Blades are made from stiff and durable composites, with glass or carbon fibers and thermoset matrices. How to heal defects in such materials?  If one can repair defects at early stages of the material degradation, one can avoid expensive composite repair at later stages. In our new article ”Healable polymer blends for structural applications”, Yulin Sun and I investigate the potential of thermoset/thermoplastic polymer blends as a basis for healable composites for challenging service conditions. We developed a computational model of damage healing in materials. Link:  https://doi.org/10.1016/j.ijmecsci.2025.109938 - 10.1.2025

2025 is starting soon. Looking back - what did we achieve in 2024? 

• New computational model of chemical recycling of composites, which allows optimization of recycling technologies, was published in “Advanced Engineering Materials” (“Modeling the solvolysis of composite materials of wind turbine blades”, https://doi.org/10.1002/adem.202302150), by Yi Chen and me,

• New research project “PREMISE “Preventing MIcroplastic pollution in SEa water from offshore wind” started in May 2024 (https://wind.dtu.dk/newsarchive/2024/06/project-premise),

• I started my course “Micromechanics of composites: from computational modelling to new materials and technbologies”, for Master Students of Mechanical Engineering at the Technical University of Darmstadt, https://www.linkedin.com/posts/mishn_micromechanics-of-composites-modelling-activity-7229394329637703681-NABN?utm_source=share&utm_medium=member_desktop

• Investigation of microplastic emission due to the surface erosion of wind blades, and estimation of the volume of eroded plastic, published in “Energies” (“Microplastic emission from eroding wind turbine blades”, https://www.mdpi.com/1996-1073/17/24/6260

• Collaboration with IIT Delhi: We studied residual stresses and viscoelastic effects in repaired wind turbine blades. The article was published in Composites Part C (“Cure-induced residual stresses and viscoelastic effects in repaired wind turbine blades: Analytical-numerical investigation”, https://doi.org/10.1016/j.jcomc.2024.100521),

• Organized International Conference on Sustainable Wind Turbine Blades: New Materials, Recycling and Future Perspectives, 18-20.11.2024, https://www.conferencemanager.dk/recyc2,

• 5th  International  Symposia on Leading Edge Erosion of Wind Turbine Blades took place at February 6-8, 2024 https://www.conferencemanager.dk/5lee. Now, Charlotte and I prepare 6th Symposium: https://www.conferencemanager.dk/6lee,

• Collaboration with ORE Catapult: Antonios Tempelis, Kristine, I and OREC colleagues published an article ., How leading edge roughness influences rain erosion of wind turbine blades?, in “Wear” (https://doi.org/10.1016/j.wear.2024.205446),

• Collaboration with Sapienza University Roma: Daniele Tortorici stayed at DTU several months, and the paper “Recycling carbon fibers by solvolysis: effects of porosity and process parameters” has been accepted at Composites Part A.

• And several more publications.

It was quite a productive year.

Merry Christmas and Happy New Year! 🎄 20.12.2024

Microplastic emission due to offshore wind turbine blades

There are some wild rumors about hashtag#microplastic hashtag#emission from wind energy. We decided to calculate, how much microplastic can fall into water due to wind turbine blade erosion. Two new estimation methods were developed: direct and indirect. Direct method is based on modelling of rain erosion, as multiple liquid impacts, leading to the stress waves and local damage of polymers. Indirect method is based on empirical data from wind turbine service companies. If a blade needs to be repaired N times per year (in real life, N varies from 0.15 to 0.4), and, when each repair starts, a technician sees that volume V was worn out from the blade surface, then the volume of eroded microplastic is N*V. Our estimations shows that between 30 and 600 gramm per blade per year are removed, which yields 1.7 tonnes for all wind turbines in all of Denmark. Is it a lot? Let us compare it with other plastic emission sources. Car tires can emit up to 1700 tones plastic per year into the sea. Textiles bring 60 tones per year. Paints bring 390 tones per year. All this is one, two or three orders of magnitude larger, than the estimated hashtag#plastic hashtag#emission from wind turbines. Our new articles was published in the journal “Energies”: https://www.mdpi.com/1996-1073/17/24/6260 . The project PREMISE is funded by VELUX FONDEN. 15.12.2024

Maintenance and repair of wind turbne blades: Danish-Indian collaboration

With the expansion of wind energy industry, maintenance and repair of wind turbines acquire special significance. How to optimize the repair technology, reduce costs, ensure quick and efficient maintenance, improve quality of blade repair and post-repair lifetime? In our current project Maintainergy ("Maintenance and Repair Strategy for Wind Energy Development"), the strategy, technology and solutions for maintenance and repair of wind turbines in Europe and in India are investigated. Here is the overview of the project results. The partners are DTU Wind and Energy Systems (coordinator), Clobotics Wind Services, WiSH Energy Solutions Private Ltd, Windcare India, IIT Delhi, CSIR India and National Institute of Wind Energy. The project is supported by the Ministry of Foreign Afairs of Denmark, in the framework of Danida Fellowship Centre grant. The main directions included understanding the wind turbine failure mechanisms, methods of extension of the blade lifetime and prevention of defects, improvement of repair, bonding and curing technologies, and optimization of maintenance and repair strategies. The project webpage is here.  6.2024.

How to reduce the maintenance and repair costs of wind turbine blades? 

First, by reducing time and increasing efficiency of each blade repair. Second, by improving repair quality, so that the next repair is needed not in 2, 5 or 7 years, but rather in decades. Physically, repair represents a rather complex process, including composite grinding, adhesive bonding, flow and curing of polymers, heat flow, phase transitions. If a technician increases the curing temperature during the blade repair, it can shorten the repair time (reducing costs), but it leads to higher residual stresses in the composite, ultimately reducing post repair lifetime. If the curing temperature is reduced, longer curing might be necessary, leading to larger voids in the composite and higher costs. This is the process, which we study and optimize in several projects. In our newest publication “Cure-induced residual stresses and viscoelastic effects in repaired wind turbine blades” (https://doi.org/10.1016/j.jcomc.2024.100521 ), we analyze the residual stresses induced during repair of wind turbine blades, and the post-repair mechanical behaviour. It was observed that temperature cycles of adhesive curing can have significant effect on the post-repair lifetime. Our other publications in this area:

• L. Mishnaevsky Jr., How to repair the next generation of wind turbine blades, Energies 2023 (about repair of recyclable wind blades, https://doi.org/10.3390/en16237694 )

• D. Paul et al., Post-repair residual stresses and microstructural defects in wind turbine blades, Int J Adhesion & Adhesives, 2023 (residual stresses and effect of voids, https://doi.org/10.1016/j.ijadhadh.2023.103356 )

• L. Mishnaevsky Jr. et al, Technologies of wind turbine blade repair: practical comparison. Energies. 2022 (comparing different repair technologies, https://doi.org/10.3390/en15051767 )

• R. Muthu et al, Repair of wind turbine blades: Experience and observations from India – A Review. Wind Energy Science (practical observations in India) (https://wes.copernicus.org/preprints/wes-2024-55/)

• L. Mischnaewski, L. Mishnaevsky Jr., Structural repair of wind turbine blades: Effects of adhesive and patch properties on the repair quality, Wind Energy, 2021 (modelling of repair and effect of voids, https://onlinelibrary.wiley.com/doi/10.1002/we.2575)

• L. Mishnaevsky Jr., Kenneth Thomsen, Costs of repair of wind turbine blades: Influence of technology aspects, Wind Energy, 2020 (costs of repair and optimization, https://onlinelibrary.wiley.com/doi/epdf/10.1002/we.2552)

• L. Mishnaevsky Jr., Repair of wind turbine blades: Review of methods and related computational mechanics problems, Renewable Energy, 2019  (overview, https://doi.org/10.1016/j.renene.2019.03.113 ). 3.2024

Course "Micromechanics of composites, smart composites and sustainable technologies" (MSc students, TU Darmstadt)

I teach a course ”Micromechanics of composites” for master students at the  Technische Universität Darmstadt, Department of Lightweight Engineering and Structural Mechanics (LSM). Here are the slides of the last, overview lecture, summarizing the ideas and concepts, which were studied at this course. 2.2024