Julie Teuwen

Julie Teuwen
Delft University of Technology | TU · Aerospace Structures and Materials (ASM)

About

52
Publications
17,317
Reads
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498
Citations
Education
October 2006 - November 2011
Delft University of Technology
Field of study
  • Aerospace Engineering, Design and Production of Composite Structures
September 2004 - October 2006
Delft University of Technology
Field of study
  • Aerospace Engineering, Design and Production of Composite Structures
September 2001 - September 2004
Delft University of Technology
Field of study
  • Aerospace Engineering

Publications

Publications (52)
Article
Full-text available
This study presents two novel methods for in situ characterization of the reaction-diffusion process during the co-curing of a polyetherimide thermoplastic interlayer with an epoxy-amine thermoset. The first method was based on hot stage experiments using a computer vision point tracker algorithm to detect and trace diffusion fronts, and the second...
Article
Ultrasonic welding is a promising joining technique for thermoplastic composite parts. On the way towards upscaling and industrialisation of this technology, it is crucial to understanding how it is affected by manufacturing tolerances. The objective of the research presented in this paper was to investigate the influence that misaligned adherends...
Article
Continuous ultrasonic welding is a promising high-speed and energy-efficient joining technique for thermoplastic composite structures. However, in the current state-of-the-art research on the topic numerous deconsolidation voids could be identified at the welding interface, which results in a strength knock-down. The aim of this study is, therefore...
Article
Full-text available
The leading edges of wind turbine blades are adhesively bonded composite sections that are susceptible to impact loads during offshore installation. The impact loads can cause localized damages at the leading edges that necessitate damage tolerance assessment. However, owing to the complex material combinations together with varying bondline thickn...
Article
Full-text available
Epoxies are inherently brittle materials and to overcome this brittleness, a second microphase (i.e., thermoplastic) is typically added. This modification of epoxy resin using thermoplastics results in reaction-induced phase separating morphologies in the micrometer range. In this study, the influence of the curing history, beyond phase separation,...
Article
Full-text available
Continuous ultrasonic welding is a promising technique for joining thermoplastic composites structures together. The aim of this study was to gain further insight into what causes higher through-the-thickness heating in continuous ultrasonic welding of thermoplastic composites as compared to the static process. Thermocouples were used to measure te...
Article
Full-text available
Rain‐induced leading‐edge erosion (LEE) of wind turbine blades (WTBs) is associated with high repair and maintenance costs. The effects of LEE can be triggered in less than 1 to 2 years for some wind turbine sites, whereas it may take several years for others. In addition, the growth of erosion may also differ for different blades and turbines oper...
Article
The effects of laser-induced deconsolidation on the compaction process of CF/PEEK tapes were investigated. First, tapes with different degrees of deconsolidation were manufactured using a laser heater. This procedure re- sulted in samples with different waviness, thickness, void content and surface roughness values. Then, as-received and laser-deco...
Article
In this study, the effect of rapid laser heating, which is typical during laser-assisted fiber placement (LAFP), on the micro- and meso- structure of the thermoplastic tape was investigated. Thermoplastic tapes were heated above the melting temperature with different heated lengths (30 and 80 mm and heating times (0.2 and 0.8 s) in a dedicated expe...
Article
Full-text available
Rain erosion on the leading edge of wind turbine blades is an intricate engineering challenge for the wind industry. Based on an energetic approach, this work proposes a methodology to characterise the erosion capacity of the raindrop impacts onto the leading edge blades. This methodology can be used with meteorological data from public institution...
Article
Operations and maintenance of offshore wind turbines (OWTs) play an important role in the development of offshore wind farms. Compared with operations, maintenance is a critical element in the levelized cost of energy, given the practical constraints imposed by offshore operations and the relatively high costs. The effects of maintenance on the lif...
Article
Full-text available
Rain-induced leading-edge erosion of wind turbine blades is associated with high repair and maintenance costs. For efficient operation and maintenance, erosion models are required that provide estimates of blade coating lifetime at a real scale. In this study, a statistical rainfall model is established that describes probabilistic distributions of...
Article
Full-text available
Leading edge erosion (LEE) repairs of wind turbine blades (WTBs) involve infield application of leading edge protection (LEP) solutions. The industry is currently aiming to use factory based LEP coatings that can applied to the WTBs before they are shipped out for installation. However, one of the main challenges related to these solutions is the c...
Article
The effect of thermal contact resistance (TCR) correlated to the degree of intimate contact (DIC) between the incoming tape and the substrate on the temperature history during laser-assisted fiber placement (LAFP) was investigated. A novel experimental methodology was designed to understand the effect with a non-contact method which did not influen...
Article
The rain-induced fatigue damage in the wind turbine blade coating has attracted increasing attention owing to significant repair and maintenance costs. The present paper develops an improved computational framework for analyzing the wind turbine blade coating fatigue induced by rain erosion. The paper first presents an extended stochastic rain fiel...
Technical Report
Full-text available
WINDCORE stands for "Wind turbine control strategies to reduce erosion of wind turbine blades by raindrop erosion". Limitation of the energy production during the service life of wind turbines is partly caused by the occurrence of damage to the wind turbine blade (WTB), called leading-edge erosion (LEE), as a result of rain droplet impacting the bl...
Conference Paper
Leading edge erosion (LEE) of a wind turbine blade (WTB) is a complex phenomenon that contributes to high operation and maintenance costs. The impact between rain droplets and rotating blades exerts cyclic fatigue stresses on the leading edge — causing progressive material loss and reduced aerodynamic performance. One of the most important paramete...
Article
Full-text available
Continuous ultrasonic welding is a promising high-speed and energy-efficient joining method for thermoplastic composite structures. Our aim was to identify and understand differences between the static and continuous ultrasonic welding process for thermoplastic composites. In particular, melting of the interface, consumed power and energy density,...
Article
The presence of rain-induced leading edge erosion of wind turbine blades necessitates the development of erosion models. The relative impact velocity between rain droplets and a rotating blade is an essential parameter for erosion modelling based on which the erosion damage rate of a wind turbine blade is calculated. The environmental parameters th...
Article
Full-text available
The issue of leading edge erosion (LEE) of wind turbine blades (WTBs) is a complex problem that reduces the aerodynamic efficiency of blades, and affects the overall cost of energy. Several research efforts are being made at the moment to counter erosion of WTBs such as-testing of advanced coating materials together with development of high-fidelit...
Article
Full-text available
The paper tackles the multi-objective optimisation of the cure stage of the Vacuum Assisted Resin Transfer Moulding (VARTM) process to manufacture the root insert of wind turbine blades. The aim of the study is to compare the Pareto front obtained from a pure heat transfer analysis, where temperature overshoot is an objective , with the one achieve...
Article
Full-text available
Epoxy resins are widely used for different commercial applications, particularly in the aerospace industry as matrix carbon fibre reinforced polymers composite. This is due to their excellent properties, i.e., ease of processing, low cost, superior mechanical, thermal and electrical properties. However, a pure epoxy system possesses some inherent s...
Article
Full-text available
Intimate contact development under LAFP-specific thermal and mechanical boundary conditions/interactions and the effect of process parameters are investigated. One-layer, unidirectional strips of CF/PEKK material were placed with different process parameters on a flat tool surface to create different intimate contact conditions. The concept of effe...
Article
Full-text available
The paper addresses the role played by the cure stage of a vacuum assisted resin transfer molding process in residual stresses generation. The Airstone 780E epoxy resin and Hardener 785H system broadly used in the wind turbine blade industry has been used in this study. The viscous-elastic properties of the resin have been characterized and impleme...
Conference Paper
The rain erosion on the leading edge of wind turbine blades has become a challenging engineering issue for the wind industry during the last decades. The raindrop impacts are the primary cause of surface erosion on the leading edges. These impacts start modifying the surface roughness for later changing the shape, i.e. the aerodynamic profile, of t...
Article
Full-text available
The leading edge of a fiber composite wind turbine blade (WTB) is prone to erosion damages due to repeated rain droplet impact during its service life. Such damages are critical to the blade’s aerodynamic as well as structural performance, ultimately resulting in substantial repair costs. An effective design of a coating material for WTB is necessa...
Conference Paper
The rain erosion of wind turbine blades is caused by raindrop impacts on the leading edge and is an engineering challenge for the wind industry. This erosion damage due to rainfall is directly related to the raindrop impact energy. Therefore, using an energetic approach, three different variables, namely the total kinetic energy, the kinetic power...
Conference Paper
Full-text available
Although aerospace traditionally has always had a multidisciplinary approach to engineering and design, the increasing complexity of aircraft and spacecraft and the rapid digitization within the aerospace industry has led to a large number of related engineering and scientific disciplines such as electrical engineers, computer scientist to work muc...
Article
Full-text available
Continuous ultrasonic welding is a high-speed joining method for thermoplastic composites. Currently, a thin film energy director is used to focus the heat generation at the interface. However, areas of intact energy director remain in the welded seam, which significantly lowers the weld strength, and result in a non-uniformly welded seam. To impro...
Conference Paper
Full-text available
The present paper investigates the generation of cure induced residual stresses during the cure stage of the Vacuum Assisted Resin Transfer Moulding (VARTM) process for the fabrication of ultra-thick components (i.e. 105 mm) for wind turbine blades manufacturing (i.e. root insert). The viscous-elastic material characterisation of the Airstone 780E...
Article
Full-text available
The paper deals with the influence of the convection coefficient and laminate thickness on multi-objective op-timisation of the vacuum assisted resin transfer moulding cure stage for the manufacturing of wind turbine components. An epoxy resin system widely used in the wind turbine industry has been chemically characterised and the correspondent fi...
Article
Full-text available
The present paper investigates the generation of cure induced residual stresses during the cure stage of the Vacuum Assisted Resin Transfer Moulding (VARTM) process for the fabrication of ultra-thick components (i.e. 105 mm) for wind turbine blades manufacturing (i.e. root insert). The viscous-elastic material characterisation of the Airstone 780E...
Conference Paper
Full-text available
The paper addresses the multi-objective optimization of the cure process of a Vacuum Assisted Resin Transfer Molding for components ranging from 40 to 100 mm thickness and aims to investigate the effect of thickness on the identification and quantification of a set of optimal cure profiles that minimize temperature overshoot and process time. Optim...
Article
Full-text available
Developments in the wind industry reveal intricate engineering challenges, one of them being the erosion on the leading edge of the wind turbine blades. In this review work, the main issues for the wind industry in the experimentation with respect to erosion are examined. After a historical and general overview of erosion, this review focuses on th...
Conference Paper
Laser assisted automated tape or fiber placement (LATP/LAFP) with in-situ consolidation is a promising technique for manufacturing large structures, eliminating the limitations of autoclave curing. Currently, 2-D models are mostly preferred for the thermal analysis of the process. A 3-D, transient thermal finite element model is developed to analyz...
Article
AbstractA 1‐D through‐the‐thickness transient heat transfer model is built to simulate the curing process of thick‐walled glass‐fibre‐reinforced anionic polyamide‐6 (APA‐6) composites. The temperature and the degree of polymerisation through the thickness of the composite are calculated and compared to the experimentally obtained results. The kinet...
Article
Semi-adiabatic temperature measurements are recorded and used to define semi-empirical equations for the simulation and prediction of the anionic polyamide-6 (APA-6) reaction kinetics. The resin mixture used has a long infusion window before the reaction starts. The prediction of the induction time and its corresponding initial temperature of react...
Article
Research on postprocessing of glass fiber–reinforced anionic polyamide-6 (APA-6) composites was performed in order to optimize the processing time. The two main points of investigation were the cure time and the annealing cycle. It was shown that the optimal mechanical properties (short-beam strength) coincided with the maximum degree of crystallin...
Article
Research on post-processing of glass fibre reinforced anionic polyamide-6 composites was performed, consisting of two main areas of interest: the cure time and the anneal cycle. It was shown that the maximum short-beam strength coincided with the maximum degree of crystallinity at a cure time of 90 min. Annealing close to the crystallisation temper...
Article
In order to manufacture thicker, larger and more integrated thermoplastic composite parts than currently can be achieved by melt processing, a vacuum infusion process is currently being developed at the Delft University of Technology using a reactive thermoplastic polymer called anionic polyamide-6 (APA-6). In previous studies it was demonstrated t...
Article
One of the advantages of reactive processing of thermoplastic composites is that due to in situ polymerization of a thermoplastic resin, interfacial bond formation occurs at a higher extend that can be achieved with melt processing. In other words, a thermoplastic composite can be obtained with an interface that is typical for thermoset composites....
Article
Moisture ingress in honeycomb sandwich structures is an issue that has attracted significant attention from aircraft operators, maintenance, repair and overhaul (MRO) organizations as well as the research community. A particular problem of interest has been rudders on the CF-18, where indications of moisture ingress were found in the composite sand...
Article
In previous research, the potential of glass fibre reinforced anionic polyamide-6 (APA-6) composites for use in wind turbine blades was proven. Based on polymer properties, viscosity, processing time, costs and recyclability, APA-6 composites are considered the most suitable reactive thermoplastic material candidate. However, more research is neede...

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Projects

Projects (4)
Project
The WIND turbine COntrol strategies to reduce wind turbine blade Rain droplet Erosion (WINDCORE) project aims to develop wind turbine control strategies to reduce rotor speed under very bad weather conditions. This approach extends blade lifetime while energy production loss is limited. Within the project we are developing models for leading edge erosion to determine wind turbine leading edge lifetime based on amount of rain, rain characteristics and blade tip speed and validating these models through laboratory erosion testing and in-field data validation.
Project
The goal of this special issue is to disseminate results related to experimental, numerical and theoretical developments applied to leading edge erosion science of wind turbine blades. Detailed information can be found on the link below: https://www.mdpi.com/journal/energies/special_issues/wind_turbine_blades Date: 23 September 2020 - 20 May 2021
Project
Since wind turbines are exposed to a variety of environmental effects, e.g. rain and hail, over their operational lifetime, the wind turbine blades, mainly on the leading edge, suffer the degradation process of erosion which leads to reducing aerodynamic efficiency and power production. Therefore the reduction of the erosion on the leading edge of wind turbine blades has become an essential issue for the wind turbine industry. The main aim of this project is to establish a scientific and engineering background regarding the degradation mechanism of erosion which provides useful information to the wind industry. Therefore, the development of a new erosion test facility which properly replicates the real-life conditions of the blades under rainfall is the first goal of this project. The second goal is to study the incubation period which is the period when no significant erosion occurs, determining which variables, e.g. initial surface roughness or viscoelastic behaviour, are relevant to prolong this defect-free period. Finally, the third goal is to investigate the linear erosion period in order to obtain semi-empirical models with the capacity of prediction of erosion which will be useful for the wind industry. Moreover this third model will provide helpful information to develop new protective coating systems in order to reduce the erosion rate.