Ongoing research projects


Ongoing research projects in iMMC (January 2020)

This a short description of research projects which are presently under progress in iMMC.
Hereunder, you may select one research direction or choose to apply another filter:

Biomedical engineering

Computational science

Civil and environmental engineering

Dynamical and electromechanical systems


Fluid mechanics

Processing and characterisation of materials

Chemical engineering

Solid mechanics

Research direction:
Listed keyword:
Other keyword:

List of projects related to: Processing and characterisation of materials

Development of high-toughness cryogenic alloys
Researcher: Alvise Miotti Bettanini
Supervisor(s): Pascal Jacques

Materials that can perform at extremely low temperatures are in great demand. Applications span from tanks and pressure vessels for LNG (Liquefied Natural Gas) carriers to structural materials in extreme conditions, like the upcoming exploration of Mars. In this context, it is critical to ensure very high toughness, which measures the resistance to crack propagation, at cryogenic temperatures. In this project, the experimental development of Fe-based superalloys is guided by a CALPHAD-based methodology, which allows the calculation of phase stability and phase transformation with computational models in order to reduce the experimental effort and hasten the development cycle of new materials.

The influence of diffusible hydrogen on the mechanical behavior of third generation steels with a bainitic-martensitic matrix exhibiting a TRIP effect
Researcher: Olivier Hubert
Supervisor(s): Pascal Jacques

In the automotive sector, the latest developments led to the era of third generation steels, exhibiting levels of strength up to 1200MPa, while keeping an adequate ductility. However, this new generation of steels is potentially sensitive to hydrogen embrittlement. Even though hydrogen embrittlement is studied for over 50 years now, it only starts to become an issue in the case of low alloy steels that start to reach problematic levels of strength.

The purpose of my research work is to investigate the role and the impact of the diffusible hydrogen on the mechanical behavior of third generation steels presenting a martensitic and/or bainitic matrix together with retained austenite exhibiting a Transformation-Induced Plasticity (TRIP) effect. In order to generate such microstructures, a heat treatment called "Quenching and Partitioning (Q&P)" is carried out in hydrogen-rich atmospheres. More specifically, the role of each phase on the hydrogen capture and/or diffusivity, as well as the influence of other microstructural parameters such as grain boundaries is studied.

Single phase martensitic and bainitic microstructures exhibiting different strength levels were processed. The influence of diffusible hydrogen in each microstructure is then studied either after cathodic hydrogen charging or in the case of gaseous hydrogen charging during the annealing process.

What's the influence of the microstructure on the hydrogen capture ?
How does the microstructure affect the notions of solubility and diffusivity of hydrogen ?
How does hydrogen affect the TRIP (TRansformation Induced Plasticity) effect ?

CeraMAX / Aerostream
Researcher: Matthieu Marteleur
Supervisor(s): Pascal Jacques

I am currently working on the processing and characterisation of a particular type of ceramics called MAX phases. They present an intermediate behavior between a ceramic and a metal at high temperature, providing a unique combination of functional properties.
My research projects also include Additive Manufacturing on metallic materials, particularly Al and Ti alloys. I am studying the relationship between the process parameters and the resulting microstructure and properties.

Observation and modelling of the link between microstructure evolution and strength in plastically deformed and annealed metals with fine-scale twins
Researcher: Fengxiang Lin
Supervisor(s): Laurent Delannay

This project aims at advancing the current understanding of the evolution of microstructures and strength during plastic deformation of face centered cubic metals in which fine-scale twins influence the dislocation slip activity, the stored energy, and the subsequent annealing. The fine-scale twins can be mechanical twins (e.g. in TWIP steels and high-strain-rate deformed copper) or growth twins in electro-deposited films. These fine-scale twins increase anisotropy, which promotes microscopic shear banding during plastic deformation. This project will specifically address some fundamental questions:
- What is the influence of the interplay of dislocation slip and mechanical twinning on the occurrence of microscopic shear bands (MSBs)?
- What is the influence of MSBs on the deformed microstructure (incl. rotation of twin bundles), the internal stresses, and the stored dislocation density?
- How do hardening and internal stresses (incl. “back-stresses”) develop in small-size samples compared to bulk samples?
- How do structural heterogeneities from MSBs and twin bundles affect the subsequent annealing behavior?

Micromechanical characterization of carbon fiber reinforced epoxy resins
Researcher: Jérémy Chevalier
Supervisor(s): Thomas Pardoen

Carbon fiber reinforced polymers (CFRP) are widely used in structural applications where weight is a critical factor. However, the lack of generic tools to accurately predict their failure must be compensated by heavy experimental campaigns to ensure the safety of the structures, increasing their cost. Hence, the goal of this thesis is to provide a precise understanding of the deformation and failure mechanisms of CFRP constituents in order to serve as a basis of a bottom-up approach.

Regarding the matrix, a detailed analysis of both the fracture and viscoplastic behavior is peformed to understand the underlying mechanisms responsible for its apparent mechanical behavior. In particular, a fracture criterion has been identified and validated under a large range of stress triaxialities, providing a unique failure mechanism for highly cross-linked epoxy resins. Regarding viscoplasticity, the so-called shear transformation zone (STZ) framework is used as a modelling approach to account for the nanoscale heterogeneity controlled mechanical response of glassy polymers. In parallel, macroscopic and insitu tests in a scanning electron microscope on a unidirectional composite are used to unveil the influence of the fibers on epoxy resins behavior when used as a matrix in CFRP. Lastly, nanoindentation is used both to characterize the microscale mechanical behavior of RTM6 and to perform push-out tests on single carbon fibers embedded in a polymer matrix to obtain direct a measurement of the interfaces properties.

Finite strain modelling of polymers and continuous fiber reinforced composites
Researcher: Muralidhar Reddy Gudimetla
Supervisor(s): Issam Doghri

The main thesis goal is to efficiently integrate the constitutive models of resin, fiber and fiber/matrix interface into a mulit-scale approach to predict the behavior of an uni-directional carbon-epoxy composite ply. This would require an efficient constitutive model for the resin/polymer which would address the experimentally observed features like strain-rate, temperature and pressure-dependency. So, an isotropic thermodynamically based fully coupled viscoelastic-viscoplastic model formulated under finite strain transformations was developed considering isothermal conditions, which is further extended to an anisotropic version suitable for structural composites. This model would be implemented in a multi-scale approach, with corresponding models for fiber and fiber/matrix interface, to predict softening/degradation in an uni-directional composite ply.

Definition, processing and optimization of new Fe-based alloys for biodegradable stents
Researcher: Aude Thomas
Supervisor(s): Pascal Jacques

Nowadays, cardiovascular diseases, such as atherosclerosis are very common. A possible solution to deal with that kind of disease is the implantation of a stent. Unfortunately, long-term complications such as thrombosis or restenosis can happen. So, a new solution would be biodegradable stents. These would ensure the mechanical support when required and then, disappear when the artery is healed. Materials for biodegradable stents should possess a very interesting combination of properties : a mechanical behaviour adapted to physiolgical stresses, a suitable biocorrosion rate and biocompatibility. My goal is to develop iron-based alloys with this combination of properties. This research raises different scientific questions, such as « what is the link between composition, microstructure and the multifunctional profile (mechanical behavior and biocorrosion)? ».

In my research, I investigate existing TWIP steels and also new alloys. To investigate quickly a new system, I work with a diffusion multiplet. This enables to investigate a lot of different compositions in one sample, which gives a first idea of the studied system. The mechanical properties are evaluated via tensile tests for example, while corrosion properties are analyzed via potentiodynamic tests and immersion tests. Microstructure and phases are also very important and can be revealed thanks to SEM or EBSD for example.

Viscoplasticity and strain localization in metallic thin films
Researcher: Guerric Lemoine
Supervisor(s): Laurent Delannay, Thomas Pardoen

Metallic thin films are widely used in the microelectronic industry and for surface functionalization. Owing to their very fine microstructure, thin films generally suffer of a lack of ductility and are prone to creep at room temperature. To avoid such detrimental effects in applications, their mechanical behaviors have to be characterized and modeled. Combining both experiments and simulations, my doctoral research focus on the rate dependent plasticity and the strain localization of metallic thin films. The Lab-on-chip technique is used to characterize the yield stress, the ductility, the hardening behavior and the strain rate sensitivity of Ni thin films. A localized necking model is also developed, dedicated to thin films and nano crystalline metals which aims at accounting for strain gradient plasticity effects, for grain size dependent strength, rate sensitivity and the possible contribution of creep/relaxation mechanisms. A dislocation-based crystal plasticity model has also been developed in order to study the mechanical and creep/relaxation behavior of the polycrystalline Pd thin films with high initial defect concentration, obtained by M-S Colla during her PhD thesis.

Researcher: Valentin Marchal-Marchant
Supervisor(s): Pascal Jacques

obtained his degree in engineering in materials science from the Université catholique de Louvain in 2011. Then, he accomplished his PhD under the supervision of prof. Pascal Jacques, on the study of Physical Vapor Deposition of thick copper films on steel.

His research is now focused on the development of thermoelectric materials and thermoelectric generators for energy harvesting and passive electromechanical systems. It aims at using common and non-toxic materials to generate electrical power from thermal gradients. Nowadays, attention is put on large scale applications owing to more than 7 years of research about thermoelectric materials leaded in IMAP.

The big challenge of this topic is the development of new tools and equipments for material production and assembly, and specific characterization methods. Such a wide range of different tasks can only be achieved thanks to the versatility of technical and scientific expertises of the IMAP team members as well as Lacami support.

Crystal plasticity modelling of thermomechanical fatigue in ITER relevant tungsten
Researcher: Aleksandr Zinovev
Supervisor(s): Laurent Delannay

Tungsten, selected as plasma-facing material for fusion reactors (such as ITER and DEMO), needs to possess high crack resistance and ductility under extreme operation conditions, such as high neutron flux and cyclic thermal load, which lead to material degradation. The objective of this project is to develop a finite element (FE) model capable to simulate mechanical behaviour of polycrystalline tungsten under tensile testing with the focus made on effect of test temperature and irradiation-induced defects. The input for the model is derived from experiments and lower-scale models, such as crystal plasticity (CP), molecular dynamics (MD) and dislocation dynamics (DD). A combination of FE and CP approach allows for investigation of mechanical behaviour of tungsten at the grain level.

The following scientific questions have to be addressed in the frame of this PhD project:

How does the heterogeneity of stress and strain within grains affect the cracking behaviour of tungsten under ITER-like heat loads? How can the impact of neutron irradiation defects be included in the CP model? What is the effect of texture on anisotropy of plastic deformation and fracture properties?

A macroscopic constitutive law, which describes plasticity of tungsten in the ITER-relevant temperature range, has already been constructed. Based on that, two papers have been published in peer-reviewed journals.

Enhancing transesterification reactions by pervaporation
Researcher: Wenqi Li
Supervisor(s): Patricia Luis Alconero

completed his master studies in the Katholieke Universiteit Leuven holding a degree in Materials Engineering and in Chemical Engineering. He developed his research and engineering skills through internships and academic studies. During his master studies, he gained knowledge on membrane processes and wrote a research paper based on the work of his master thesis, with the cooperation of his supervisor (prof. Patricia Luis) and promoter (prof. Bart Van der Bruggen). He was also involved as co-author in a second paper on the development of environmental friendly ink for spray coating of organic photovoltaics, which has been published in the Journal of Advanced Functional Materials. Mr. Li strongly feels that membrane processes and membrane technology are very useful in industrial processes in the present and the future. Thus, after completing his master studies, he started his PhD within the research group led by prof. Patricia Luis at the Université catholique de Louvain. The main objective of the research work is the separation of organic-organic mixtures by using pervaporation in order to achieve a high purity product and a low energy consumption process.

Study of reaction mechanisms of chemical wet etching and frosting of glass substrates
Researcher: Nicolas Piret
Supervisor(s): Joris Proost

This research project is about bringing a fundamental understanding of the glass frosting process and its different corresponding chemical processes.
Indeed, although this process is higly used in the glass industry, there is only few fundamental researches that were led on the whole glass frosting process.
This project will try to answer to these questions : What are the different chemical steps that lead to glass surface microstructuration, giving this matt aspect of a frosted glass ? What are the roles and influences of each chemical used in the etching solution on the reaction kinetics and on the glass aspect?
To try to answer to these questions the glass dissolution mecanism and its kinetics are studied via gravimetric analysis of glass substrates and ICP analysis of etching solutions. The precipitate occuring on the glass surface during the frosting, leading to the microstructuration will be characterized and its kinetics will be determined.

Study of the hardening properties, damage resistance and toughness of a new family of beta metastables titanium alloys
Researcher: Laurine Choisez
Supervisor(s): Pascal Jacques

The association of different plastic deformation modes (TRIP, TWIP) induces unmatched levels of mechanical properties in a new beta metastables titanium alloys family. A hardening beyond the theoretical limit is especially noticed, together with a uniform deformation 3 to 4 times higher than the one in a classic TA6V alloy and a yield stress superior of 30 percent to the one in a
TWIP alloy. A positive synergy is thought to exist between a high hardening and the damage resistance and toughness of such materials. My thesis will consist in the study of the damage resistance and the toughness of several beta metastables titanium alloys with different prevailing plastic deformation mechanisms in order to highlight the mechanism responsible of the post-necking deformation properties.

Coupled mechanical-electrical effects in highly strained Ge thin films
Researcher: Marie-Stéphane Colla
Supervisor(s): Thomas Pardoen

Graduated in chemical and materials science engineering at the Université catholique de Louvain in 2009 (Belgium). Then, under the supervision of Prof. Thomas Pardoen (iMMC) and Prof. Jean-Pierre Raskin (ICTEAM), she accomplished a PhD on the study of the mechanical properties of thin films, more specifically on the plasticity and creep of freestanding nanocrystalline Pd films. The lab-on-chip technique developed previously at the UCL was adapted to deform Pd thin films. After the PhD, she worked for more than two years at the CRM Group in Liège on the development of industrially viable thin film solar cells on steel. From June 2016 to September 2018, she is back at the UCL as a research engineer involved in projects dealing with the understanding of fracture behaviour of high strength steels under a wide range of strain rates.​ In 2018, she received a 'Chargée de recherches - FNRS grant' and is now working on coupled mechanical-electrical effects in highly strained germanium thin films. Germanium is a promising material for optoelectronic device owing to its compatibility with the standard complementary metal-oxyde-semiconductor (CMOS) technology and to the possibility to convert it into a direct bandgap semiconductor by straining it.

Surface mechanical treatment by friction stir processing of additive manufactured aluminium alloy parts to improve mechanical behaviour
Researcher: Juan Guillermo Santos Macias
Supervisor(s): Aude Simar, Pascal Jacques

This research project aims at improving the mechanical behaviour of additive manufactured parts through a friction stir processing (FSP) surface mechanical treatment. This post-processing method significantly enhances ductility and is expected to also enhance fatigue resistance. Fatigue is a critical phenomenon in many applications, e.g. structural parts in the aerospace industry. More specifically, this research is focused on studying the effect of FSP on the microstructure (porosity and second phase size and spatial distribution) and mechanical behaviour (residual stresses and fatigue) of selective laser melting AlSi10Mg parts. Furthermore, in order to define an adequate FSP patterning strategy, the project will also feature an analysis of the influence of processing parameters through a chained thermal and microstructural model.

Researcher: Geoffrey Roy
Supervisor(s): Pascal Jacques

Geoffrey holds a Master in Mechatronic Engineering (2010) and a PhD in Engineering (2015) from the Université catholique de Louvain where he works as a senior researcher at the Institute of Mechanics, Materials and Civil Engineering (iMMC).

Within the Division of Materials and Process Engineering (IMAP), his research is focused on the development of new thermoelectric materials and systems for a range of applications going from industrial waste heat recovery to autonomous powering of smart sensors. In his research, he pays particular attention to the development of new solutions that present improved both technical and economical profiles in order to facilitate the emergence of these solutions out of the lab.

This research is followed by several companies such as: Drever International, AGC Glass Europe, Carmeuse or Engie.

Aerostream and IAWATHA (additive manufacturing), LOCOTED (thermoelectrics)
Researcher: Camille van der Rest
Supervisor(s): Pascal Jacques, Aude Simar

Camille van der Rest completed her PhD thesis on the optimisation of Heusler Fe2VAl-based thermoelectric compounds through innovative metallurgical processing in 2015. It was under the joint supervision of Prof. Pascal Jacques and Prof. Aude Simar. Her research topics now concern thermoelectric materials, additive manufacturing and friction stir processing technologies. Concerning thermoelectrics, the main objective is the development of low-cost, non-toxic, and powerful materials that could be used in large-scale industrial applications of heat recovery. In addition, she studies some fundamental aspects in order to improve the performances of such materials, i.e. ordering phenomena in off-stoichiometric Fe2VAl-based Heusler compounds. It is essential to make the link between (innovative) manufacturing processes, microstructures and the functional properties of these TE materials. Concerning additive manufacturing, the main contributions are on the characterisation and optimisation of the microstructures and the mechanical behaviour of Al parts obtained by Selective Laser Melting and the developpment of new materials for additive manufacturing. Again, the link between the process parameters and the final microstructure/properties is a key issue. Finally, Camille developed, together with Prof. Aude Simar and Prof. Pascal Jacques, a novel Friction Melt Bonding (FMB) process in order to weld aluminium alloys and steels. This process is still under development thanks to the collaboration with other researchers of IMAP.

Crack deviation in Al alloys by Friction stir processing
Researcher: Lv Zhao
Supervisor(s): Aude Simar

Lv Zhao completed his Master and PhD degrees in Institut National des Sciences Appliquées de Lyon in 2013 and 2016. His PhD work addressed the fracture behavior of solar grade monocrystalline and multi-crystalline silicon wafers, in which a couple of innovative experimental techniques have been elaborated and new results highlighted. He is now working in the framework the ERC Starting Grant ALUFIX as post-doc fellow with Professor Aude Simar. The aim is to investigate the crack propagation in aluminum alloys in the presence of local residual stresses induced by shape memory alloy particles. His work encompasses an experimental part in which metal matrix composites (MMCs) are manufactured by friction stir processing, and a numerical part in which the cohesive zone method is applied to address the crack path within the MMCs in the framework of finite element modeling.

Characterization and modeling of surface mechanical properties at the micro-nanometer scale for the study of polymer and composite behavior in contact with industrial fluids
Researcher: Céline Vlémincq
Supervisor(s): Thomas Pardoen

Currently the characterization of the mechanical properties of polymers after ageing with fluids is long and costly, as it is essentially based on the macroscopic characterization of saturated samples. In this context, the objective of the project is to exploit the potential of local methods to evaluate the evolution of the surface mechanical properties, through nanoindentation and atomic force microscopy (AFM), and to establish assessment protocols for the quantification of the impact of fluids on mechanical properties. With these local methods, the aging time could be reduced from months to a few minutes.

To achieve this objective it will be necessary to establish a modeling strategy based on a micro-mechanical basis. The aim of the modeling approach is to link nano- and microscopic measurements to the elasto-viscoplastic properties and to understand the root causes of the fluid impact on physical mechanisms.

Researcher: Pierre Bollen
Supervisor(s): Thomas Pardoen

graduated as engineer in chemistry and materials science at Université catholique de Louvain (Belgium) in 2010. In 2015, he obtained at UCL his PhD thesis entitled hierarchical hybrid materials combining wideband electromagnetic absorption and mechanical performance, funded by a FRIA grant. After working one year as a support engineer in the field of extended finite element modeling, he came back at the UCL as a senior researcher involved in applied research projects in collaboration with industry. He is currently dealing with erosion coating on CFRP as well as thermal and electromagnetic management in electrical power converter.

Researcher: Vincent Destoop
Supervisor(s): Thomas Pardoen

made his PhD on the adhesion of tooth-filling materials to the dentine. He’s now working on composite materials to replace metals in aircraft applications. He takes part to projects studying the mechanical behavior of composite materials (mainly polymer matrix reinforced with long fibers) which are new candidate materials for modern planes. His investigations focus on their bulk, cracking, impact and adhesion properties.

Preforming of composite thermoset prepreg fabrics.m
Researcher: Catherine Doneux
Supervisor(s): Thomas Pardoen

Graduated as Civil Engineer at University of Liege in 1992,C. Doneux began her career with a first experience on the assessment of an existing prestressed railway bridge. Thanks to several FNRS grants, she obtained a PhD degree in the domain of steel-concrete composite structures under seismic action in 2002 and was involved in several researches on paraseismic design at ULg until 2005. After some career break, she joined UCL in December 2008 to take part to the development of new composite activities related to various applied research projects in collaboration with the industry (aeronautics). Her main fields of expertise are the mechanical characterization of composite materials by mechanical testing, the quality control of the standardised tests and the development of new tests. She has also some experience in fatigue testing, damage characterization and fracture mechanics. She is currently working on the preforming of composite thermoset prepreg fabrics.

Researcher: Audrey Favache
Supervisor(s): Thomas Pardoen

obtained a PhD degree in the domain of process control in 2009 at Université catholique de Louvain (Belgium), after having graduated there as chemical engineer in 2005. Since then, she is working as a "senior" researcher on several applied research projects in collaboration with the industry in the domain of mechanics of materials. More particularly, she is interested in the link between the mechanical properties of the individual components of a complex system and the global mechanical response of this system. She applied this approach to the framework of tribology and contact mechanics for understanding the scratch resistance of coatings and multilayered systems. Her work covers both experimental aspects and finite element simulations.

Researcher: Thaneshan Sapanathan
Supervisor(s): Aude Simar

completed a mechanical engineering degree and a PhD at Monash University (Australia) in 2010 and 2014, respectively. His thesis was entitled “Fabrication of axi-symmetric hybrid materials using combination of shear and pressure”. During his PhD, he worked on architectured hybrid materials fabrication using severe plastic deformation (SPD) processes. Two novel axi-symmetric SPD techniques were investigated to fabricate hybrid materials with concurrent grain refinements. After that, he started a research project at University of Technology of Compiègne (France) in which he investigated the weldability window for similar and dissimilar material combinations using numerical simulations for magnetic pulse welding. He also studied the interfacial phenomena, behavior of material under high strain rate deformation, modeling and simulation of the magnetic pulse welding/forming. Then, I was working as a postdoctoral research fellow at UCL on the topic of characterizations of aluminium to steel welds made by friction stir welds and friction melt bonding. At present, I am working as a FNRS reserch officer (Chargé de recherche) and investigating intermetallic induced residual stresses and mitigation of hot tear in innovative dissimilar joints.

Renforcement des capacités de RDI des organismes de recherche dans les domaines utiles aux PME
Researcher: Michaël Coulombier
Supervisor(s): Thomas Pardoen

graduated as a material science engineer from UCL in 2006. He finished his PhD in 2012 under the supervision of Prof. Thomas Pardoen (iMMC) and Prof. Jean-Pierre Raskin (ICTEAM) developing a lab on-chip technique for nano-mechanical characterisation of thin films. Since then he has been a research assistant in iMMC involved in various projects dealing with material science, nanomechanical testing and tribology.

Recycle more plastics from residual waste/ Bio-sourced polymer composites
Researcher: Naïma Sallem
Supervisor(s): Patricia Luis Alconero, Thomas Pardoen

holds a PhD in Materials Sciences from the University of Lille 1 in France in 2008, in collaboration with l’Ecole des Mines de Douai. The theme of her works was to establish the relationships between the mechanical behavior, structural and macromolecular orientation of multilayer films composed of Polyamide 6 and Polyethylene for the food packaging industry. Then, she worked as research assistant at the BSMA institute at UCL on Walloon Region projects concerning reactive extrusion, polymer nanocomposites, polymer from biomass waste. She is now working on Life Cycle Assessment (LCA) and studying the environmental impacts of recycling the plastics from residual waste and she is involved in a project based on bio-sourced composites.

Friction stir processing based local damage mitigation and healing in aluminium alloys
Researcher: Matthieu Baudouin Lezaack
Supervisor(s): Aude Simar

Al 7XXX alloys will be characterized before and after friction stir process (FSP) in order to identify the damage mechanisms. The performances of FSPed alloys will be studied by macromechanical testing. Up to now, a 150% increase in ductility was reached by FSP + heat treatments compared to the base 7475 Al material. Then a numerical model will catch the 7XXX aluminium behavior in a close future.

Influence of defects on the life of biomedical implants
Researcher: Maïté Croonenborghs
Supervisor(s): Pascal Jacques, Thomas Pardoen

Implants are devices aiming to support, help or even correct biological structures. However, with time, some of these implants show aging problems. The roots of these problems can have numerous explanations. In some cases, the body reacts to the presence of a foreign body, and this can lead to health risks. Sometimes, the material can show, with time, signs of weakness. Later on, these defects can lead to the failure of the implant.

In the case of permanent stent implants, the presence of a foreign body in the blood vessels can lead to restenosis or late thrombosis. This is why bioresorbable stents are nowadays developed. These stents should support the vessels during their healing period and dissolve in an inoffensive way afterwards. Iron-based alloys are investigated for their appropriate mechanical properties but their degradation rate is too low. One investigated solution is to increase surface roughness to dissolve faster the implant. The effect of this roughness on the expansion process has not been analyzed for now.

The case of growth rods shows that the material itself can lead to implant failure. These rods are placed, during a surgery, along the spine of scoliotic children. They aim to support the spine and help it to straighten back. However, fracture events occur in 36% of the patients. During the surgery, the rods are bent to fit to the natural shape of the spine. The tools employed for this process can introduce some indentation marks on the surface of the rods and decrease their fatigue lifetime.

From these case studies, it is observed that the completion of an implant (i.e. stent implantation process) or its lifetime (i.e. growth rod failure) can be affected by its surface state. This research will therefore focus on the imperfection sensitiveness of such devices. Various kinds of defects are introduced at the sample surface. To understand the influence of these defects on the mechanical properties, these samples are tested and compared.

Fracture toughness of high entropy alloys
Researcher: Antoine Hilhorst
Supervisor(s): Pascal Jacques, Thomas Pardoen

High entropy alloys (HEAs) are a new family of metallic alloys. In contrast to conventional alloys, HEAs have multiple principal elements e.g. the equiatomic "Cantor" alloy CrMnFeCoNi. Alloys in this range of chemical composition have gathered attention only recently. From what was observed in conventional alloys, it was expected that HEAs microstructure be composed of several intermetallic phases but some systems are surprisingly single phase solid solution. Moreover, such single-phase alloys have excellent mechanical properties. For instance, CrMnFeCoNi possess a large fracture toughness, which increases with decreasing temperature, putting this alloy on par with the current best alloys used for cryogenic applications. As such, the objective of the thesis is to understand the underlying mechanisms responsible for the observed macroscopic behavior of such alloys.

The thesis aims to answer several questions such as: What are the mechanisms responsible for the increase in ductility, strength, and fracture toughness with decreasing temperature? What high-throughput methodology would be able to screen the vast range of possible chemical composition of HEAs for high performance alloys?

To understand the deformation mechanisms, several HEAs will be fully characterized from casting to mechanical testing. For the fracture toughness measurements, the essential work of fracture method will be employed as it is best suited for ductile thin sheets than compact tests. Diffusion multiples will be explored as a possible high-throughput method, as the presence of composition gradients allows the simultaneous characterization of a range of composition by techniques such as EDX, EBSD and nano-indentation.

Optimisation of the corrosion rate of iron-based alloys for bioresorbable stent applications
Researcher: Sarah Reuter
Supervisor(s): Pascal Jacques

The purpose of this PhD thesis is to optimise the metallic surface of iron-based alloys that are good candidates for bioresorbable stents but which corrosion properties are still insufficient. I will thus be working on these alloys by improving their surface properties, by acidifying the surface. Indeed, the corrosion products and salt compounds get deposited due to a neutral/basic environment in the close vicinity of the metal surface. These compounds act as a barrier for further corrosion. By acidifying the metallic surface, this would inhibit, or at least diminish, the deposition of these compounds. The corrosion properties of these metals will be studied by the use of electrochemical tests as well as immersion tests. The surface will be acidified by the presence of protons. This will be done by adding hydrogen in the metal. Nevertheless, the presence of hydrogen is known to weaken the metal. In order to avoid this weakening, the hydrogen will be trapped inside the steel.

This project englobes different disciplines and is made alive thanks to close collaboration with different entities of the UCL.

On a chip fracture mechanics test method
Researcher: Sahar Jaddi
Supervisor(s): Thomas Pardoen

The aim of this research is to develop a new testing method based on an-on-chip concept to measure the fracture toughness of freestanding submicron films. This device consists of two major components, a notched specimen and two actuators. When the test structure is released by etching the sacrificial layer, the two actuators contract, this in turn loads the specimen in traction. In order to define the stress intensity factor expression, which is given by this new model, analytical analysis and finite element simulations must be performed in addition to the experimental part, which is based on the microfabrication techniques. Silicon nitride, silicon oxide and metallic glass thin films will be studied during this work. The major goal of this model is to extract fracture toughness of 2D materials like graphene.

Electromechanical properties of thin films
Researcher: Farzaneh Bahrami
Supervisor(s): Thomas Pardoen

The production of Graphene/h-BN heterostructures and the investiong of their microelectromechanical properties, the production of origami and kirigami stacks of Graphene and h-BN, the raman spectroscopy, SEM, TEM AFM and nanoindentation will be used

Development and qualification of irradiation tolerant tungsten and novel toughness-enhanced composites for fusion applications
Researcher: Chao Yin
Supervisor(s): Thomas Pardoen

This research aims at investigation of the radiation damage and post-irradiation mechanical-thermal behavior of tungsten. Tungsten selected as the first wall armor and Tungsten-based composites for structural applications in DEMO are expected to receive doses up to 20 dpa (Fe) (for the EARLY DEMO) or even higher (full power DEMO) [1]. Under these conditions, the mechanical properties of the materials are known to degrade radically due to (i) neutron irradiation, (ii) heat transients, (iii) plasma gas uptake and (iv) nuclear transmutation. Thus, this investigation is called by the need to validate the performance of novel and baseline garde tungsten. This project will include the experiemental study of reference and irradiated materials carried out by mechanical test and microstructure investigation.

Improving the properties of glass fiber reinforced acrylic thermoplastic resin based composites
Researcher: Sarah Gayot
Supervisor(s): Thomas Pardoen

For the manufacturing of continuous fiber reinforced thermoplastic composites (CFRTP), certain monomers can be infused through glass fabric and then polymerized in situ, in order to make a thermoplastic composite part. However, defects - e.g. porosity - can occur in the material, due to the thickness of the laminates and the shrinkage of the resin matrix during polymerization. Such phenomena must be understood, as well as their effects on the mechanical properties of the final composite part.

The originality of this work lies in the very nature of the polymeric matrix used for manufacturing the composite parts, which is thermoplastic instead of thermoset. Little is known about the behaviour of such thermoplastic composites, especially at a microscopic scale. During this PhD, we will try to understand how defects occurring in the material can influence the structural properties of the CFRTP, and we will try to mitigate (or at least control) the incidence of such defects. This will imply a better knowledge of how usual characterisation techniques can be applied from thin to thick composite parts. In particular, digital simulation will be used so as to predict the properties of thick composite parts from those of thinner samples.

Contribution in to development of new medium steels of third generation of advance high strength steels for weightlighting automotive structure
Researcher: Hamza Essoussi
Supervisor(s): Hosni Idrissi, Pascal Jacques

Partout dans le monde il y a un intérêt croissant pour développer de nouveaux aciers : les aciers avancés à haute résistance (Advanced High Strength Steel « AHSS ») pour plusieurs applications, en particulier l’industrie automobile. En conséquence, la recherche est en cours dans les universités, instituts de recherche et les entreprises. Pourquoi donc ces matériaux sont sélectionnés pour les applications automobiles ? Plusieurs facteurs entraînent l’utilisation des AHSS pour les véhicules. Dans un premier lieu leur utilisation contribue à la réduction du poids du véhicule et du coup la réduction de la consommation du fuel et donc la réduction de l’émission du dioxyde du carbone CO2 émis dans l’atmosphère. Non seulement cela mais aussi leur grande résistance aux chocs et leur meilleure performance augmente la sécurité des passagers et tout cela avec un coût minimal de production. La troisième génération des aciers avancés (3rd generation of AHSS) a une structure composée, en particulier leur microstructure qui est généralement une microstructure multiphase dans le but d’avoir une combinaison parfaite entre résistance et ductilité pour qu’ils soient adaptés aux différents procédés de mise en forme (formage de tôle, soudage…) et les commercialiser. La troisième génération des AHSSs contient des quantités considérables des éléments contribuant à augmenter leur résistance, comme : la martensite, la bainite et ferrite. Le comportement composé de la structure multiphase et de l’effet TRIP (Transformation Induced Plasticity) ou l’effet TWIP (Twinning Induced Plasticity) lié à la présence de l’austénite résiduelle permet d’obtenir un excellent compromis entre résistance et ductilité qui est désiré pour les procédés de formage.