Ongoing research projects
Ongoing research projects in iMMC (February 2021)
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:
List of projects related to: micromechanics
|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.
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.
|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.
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.
|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.
|Deformation and failure of polymeric and metallic glasses|
Researcher: Frederik Van Loock
Supervisor(s): Thomas Pardoen
My research work is focused on the deformation and fracture of (glassy) polymeric materials and polymer-based hybrid material concepts such as polymeric foams, adhesive joints, and fibre-reinforced polymer composites. Some current research topics include:
i) The development of a mesoscale constitutive finite element model based on the concept of shear transformation zones (STZs) for glassy materials (polymers and metals). The STZ model allows to predict the complex large deformation response of glassy polymers, including post-yield softening and non-linear unloading behaviour, by calibration of a few parameters via experiments on the polymer of interest. The model also sheds light on the interactions between discrete and elementary distortion mechanisms (and their collective organisation) during plastic deformation of polymeric glasses. Ongoing research with the STZ model includes ageing (and mechanical rejuvenation) of polymers, viscoelastic effects, and the effect of confinement due to the presence of fibres on the constitutive response of glassy polymers. The STZ modelling approach is also being used to study deformation and fracture of confined layers of metallic glasses.
ii) Fracture problems in polymers and fibre-reinforced polymer composites.
iii) The development of a thermochemical model for the in-situ polymerization of a thermoplastic matrix in a fibre-reinforced polymer composite (PhD work of Sarah Gayot).
iii) Fracture problems in solder joints subjected to thermal cycling (PhD work of Vincent Voet).
|Development of thermo-tensile nano devices operating ex situ or in situ in transmission electron microscopes (TEM)|
Researcher: Alex Pip
Supervisor(s): Hosni Idrissi
The main goal of my research project is to develop modern miniaturized devices dedicated to quantitative small-scale thermo-tensile testing in-situ inside a transmission electron microscope. These unique devices will be used to investigate the effect of T on the plasticity/failure mechanisms in selected materials, nanocrystalline palladium films and olivine. My project builds up on already existing MEMS devices, namely the commercial Push-to- Pull from Bruker.Inc and UCLouvain’s ‘lab-on-chip’ nano tensile testing devices. Currently, those devices are limited to room temperature experiments. My work will be dedicated to the integration of heating systems inside these two devices, in order to heat samples up to hundreds of °C. This will allow performing in-situ TEM thermo-tensile tests on Pd films and olivine samples where the coupling between tensile loading and heating could lead to unprecedented results regarding the effect of T on the mechanical response and the plasticity/failure mechanisms.
This project has a direct application in the field of geology, as one of the selected material is olivine, the material that makes up most of the upper part of the Earth’s mantle. Thermo-tensile testing of olivine at the micro/nano scale will bring crucial data about its rheology under conditions similar to the Earth’s mantle. This part of the project involving olivine will be performed in close contact with prof. Patrick Cordier and his team at UMET (Université de Lille). The other selected material is Pd, a material that is well known by the UCLouvain’s IMMC researchers used here as a benchmark. I will mostly work within the WINFAB platform, where I will develop and build the new thermo-tensile devices using the nanofabrication equipment. As theses devices are expected to be used in-situ inside a TEM, I will also partly work at the EMAT research center (UAntwerpen).
|Analysis and understanding of the damage and fracture mechanisms in advanced high strength steels for automotive applications|
Researcher: Thibaut Heremans
Supervisor(s): Pascal Jacques, Thomas Pardoen
The environmental challenge the world is facing today is driving car manufacturers to limit their vehicule weight in order to reduce their fuel consumption. As a consequence, steels with higher specific strength performances are being constantly developed, while insuring that proper ductility and toughness levels are retained to allow for forming operations and passengers safety. Lately, the so-called "third generation" of advanced high strength steels (AHSS) has emerged, among which one finds the Quenching & Partioning (Q&P) steels. These Q&P steels demonstrate an excellent combination of ultimate tensile strength (UTS = 1500 MPa) and adequate ductility (TE = 18%). Nevertheless, their fracture properties and the underlying mechanisms are still not fully understood and start raising concerns as the strength levels of these steels increase. Indeed, recent studies have highlighted a shift in failure mechanism, from ductile to brittle, depending on the loading conditions. Although often left behind strength and elongation, toughness issues constitute essential stakes not only for ever more demanding applications but also for forming processes during which edge cracking is a key concern. The objective of my research project is to investigate the failure properties of these Q&P steels in order to understand how microstructural and micromechanical parameters influence the competition between three possible mechanisms : ductile flat, ductile slant and brittle intergranular.