Ongoing research projects
Ongoing research projects in iMMC (July 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:
List of projects related to: micromechanics
|Characterization and physics based modeling of plasticity and fracture of Dual-Phase steels towards ultratough materials by microstructure optimization|
Researcher: Karim Ismail
Supervisor(s): Thomas Pardoen, Pascal Jacques
The research work, in collaboration with company ArcelorMittal, is about the plasticity, the damage and the crack propagation resistance of dual-phase steels, which are commonly used in the automotive industry. A minimum level of fracture toughness is required to prevent the propagation during forming operations of small edge damage or cracked zones induced by cutting. Therefore, unravelling the relationship between fracture toughness, microstructure and damage mechanisms is essential to develop advanced steels with superior forming ability. Furthermore, reaching superior fracture toughness could open to other potential applications.
Experimental works as well as computational modeling are used to study the behavior of such steels. A model for the plastic behavior and for the damage mechanisms related to the microstructure has been developed. A finite element based unit cell approach is used to address the plastic behavior, locally as well as at the macroscopic scale. A particular focus is put on the effect of particle morphology and orientation that have not been much investigated and that considerably affect local mechanical fields, and hence damage and fracture behavior. A two-stage void coalescence process is suggested in elongated microstructures. The data extracted from the elastoplastic analysis are fed into a cellular automaton approach of the damage evolution. This model introduces a statistical description of the material while using relatively simple damage evolution laws. Furthermore, the essential work of fracture method is used to quantify the resistance to the propagation of a crack on thin sheets. Martensite morphology in the form of platelets seems to be a means to reach a high fracture toughness. Finally, damage mechanisms are observed post-mortem and hole expansion ratio tests will be performed.
|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).