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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Fri, 12 Jul 2024 13:52:13 GMT2024-07-12T13:52:13ZExperimental characterization and thermoviscoelastic modeling of strain and stress recoveries of an amorphous polymer network
http://hdl.handle.net/10985/7357
Experimental characterization and thermoviscoelastic modeling of strain and stress recoveries of an amorphous polymer network
ARRIETA, Juan Sebastian; DIANI, Julie; GILORMINI, Pierre
An acrylate polymer network was submitted to thermomechanical shape memory cycles. The set of experiments characterized the material stress-free strain recovery and the strain-constrained stress recovery in uniaxial tension. Experimental parameters like temperature of strain fixation, amount of strain and heating rate, were varied in order to provide a relatively complete set of experimental data. A model combining the amorphous polymer viscoelasticity and its time–temperature superposition property was used to predict the shape memory behavior of the acrylate polymer network. All the model parameters were characterized using classical tests for mechanical characterization of polymers, which do not include shape memory tests. Model predictions obtained by finite element simulations compared very well to the experimental data and therefore the model relevance for computer assisted application design was assessed.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/73572014-01-01T00:00:00ZARRIETA, Juan SebastianDIANI, JulieGILORMINI, PierreAn acrylate polymer network was submitted to thermomechanical shape memory cycles. The set of experiments characterized the material stress-free strain recovery and the strain-constrained stress recovery in uniaxial tension. Experimental parameters like temperature of strain fixation, amount of strain and heating rate, were varied in order to provide a relatively complete set of experimental data. A model combining the amorphous polymer viscoelasticity and its time–temperature superposition property was used to predict the shape memory behavior of the acrylate polymer network. All the model parameters were characterized using classical tests for mechanical characterization of polymers, which do not include shape memory tests. Model predictions obtained by finite element simulations compared very well to the experimental data and therefore the model relevance for computer assisted application design was assessed.On modeling shape memory polymers as elastic two-phase composite materials
http://hdl.handle.net/10985/6558
On modeling shape memory polymers as elastic two-phase composite materials
GILORMINI, Pierre; DIANI, Julie
A model has been proposed recently, which describes the experimentally observed mechanical behavior of some shape memory polymers. It considers a purely thermoelastic behavior, without strain rate effects, and assumes essentially that the polymer can be considered as a two-phase composite, with glassy and rubbery phases having volume fractions that depend on temperature only. Since a uniform stress hypothesis was used in the original formulation, with an inconsistency when thermal expansion was considered, this model is revisited here by taking advantage of the many results that have been established in the theory of composite materials. It is shown, especially, that a uniform strain hypothesis is more appropriate than assuming a uniform stress.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/65582012-01-01T00:00:00ZGILORMINI, PierreDIANI, JulieA model has been proposed recently, which describes the experimentally observed mechanical behavior of some shape memory polymers. It considers a purely thermoelastic behavior, without strain rate effects, and assumes essentially that the polymer can be considered as a two-phase composite, with glassy and rubbery phases having volume fractions that depend on temperature only. Since a uniform stress hypothesis was used in the original formulation, with an inconsistency when thermal expansion was considered, this model is revisited here by taking advantage of the many results that have been established in the theory of composite materials. It is shown, especially, that a uniform strain hypothesis is more appropriate than assuming a uniform stress.Predicting thermal shape recovery of crosslinked polymer networks from linear viscoelasticity
http://hdl.handle.net/10985/6559
Predicting thermal shape recovery of crosslinked polymer networks from linear viscoelasticity
DIANI, Julie; GILORMINI, Pierre; FREDY, Carole; ROUSSEAU, Ingrid
The viscoelastic behavior of an amorphous shape-memory polymer network and its dependence on time and temperature were measured by dynamic mechanical analysis. The resulting thermomechanical behavior was modeled and implemented in a commercial finite element code. The ability of the resulting thermomechanical model to simulate and, eventually, predict the shape storage and shape recovery of the material was evaluated by comparison with experimental shape memory thermomechanical torsion data in a large deformation regimen. The simulations showed excellent agreement with experimental shape memory thermomechanical cycle data. This demonstrates the dependence of the shape recovery on time and temperature. The results suggest that accurate predictions of the shape recovery of any amorphous polymer networks under any thermomechanical conditions combination solely depends on considering the material viscoelasticity and its timetemperature dependence.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/65592012-01-01T00:00:00ZDIANI, JulieGILORMINI, PierreFREDY, CaroleROUSSEAU, IngridThe viscoelastic behavior of an amorphous shape-memory polymer network and its dependence on time and temperature were measured by dynamic mechanical analysis. The resulting thermomechanical behavior was modeled and implemented in a commercial finite element code. The ability of the resulting thermomechanical model to simulate and, eventually, predict the shape storage and shape recovery of the material was evaluated by comparison with experimental shape memory thermomechanical torsion data in a large deformation regimen. The simulations showed excellent agreement with experimental shape memory thermomechanical cycle data. This demonstrates the dependence of the shape recovery on time and temperature. The results suggest that accurate predictions of the shape recovery of any amorphous polymer networks under any thermomechanical conditions combination solely depends on considering the material viscoelasticity and its timetemperature dependence.Experimental and modelling studies of the shape memory properties of amorphous polymer network composites
http://hdl.handle.net/10985/8458
Experimental and modelling studies of the shape memory properties of amorphous polymer network composites
ARRIETA, Juan Sebastian; DIANI, Julie; GILORMINI, Pierre
Shape memory polymer composites (SMPCs) have become an important leverage to improve the development of shape memory polymers (SMPs) applications. An amorphous SMP matrix has been filled with different types of reinforcements in this study. An experimental set of results is presented and then compared to 3D finite element simulations. Thermomechanical shape memory cycles were performed in uniaxial tension. The fillers effect was studied in stress-free and constrained-strain recoveries. Experimental observations indicate complete shape recovery and put in evidence the increased sensitivity of constrained length stress recoveries to the heating ramp on the tested composites. The simulations reproduced a simplified periodic reinforced composite and use a model for the matrix material that has been previously tested on regular SMPs. The latter combines viscoelasticity at finite strain and time-temperature superposition. The simulations permit to represent the recovery properties of a reinforced SMP easily.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/84582014-01-01T00:00:00ZARRIETA, Juan SebastianDIANI, JulieGILORMINI, PierreShape memory polymer composites (SMPCs) have become an important leverage to improve the development of shape memory polymers (SMPs) applications. An amorphous SMP matrix has been filled with different types of reinforcements in this study. An experimental set of results is presented and then compared to 3D finite element simulations. Thermomechanical shape memory cycles were performed in uniaxial tension. The fillers effect was studied in stress-free and constrained-strain recoveries. Experimental observations indicate complete shape recovery and put in evidence the increased sensitivity of constrained length stress recoveries to the heating ramp on the tested composites. The simulations reproduced a simplified periodic reinforced composite and use a model for the matrix material that has been previously tested on regular SMPs. The latter combines viscoelasticity at finite strain and time-temperature superposition. The simulations permit to represent the recovery properties of a reinforced SMP easily.Legitimate domain of a Newtonian behavior for thermal nanoimprint lithography
http://hdl.handle.net/10985/7175
Legitimate domain of a Newtonian behavior for thermal nanoimprint lithography
TEYSSEDRE, Hubert; GILORMINI, Pierre; LANDIS, Stefan; REGNIER, Gilles
Nanoimprint lithography is an efficient way to reproduce nanostructures down to 20 nanometers in sub-micrometer polymeric films. To optimize this process, simulation using a Newtonian behavior is a cheap and efficient way to predict the polymer flow in micro and nano size cavities. This behavior is nevertheless limited to flows with shear rates below a critical value that can be determined with standard rheology measurements. We have investigated the validity domain of this behavior to simulate thermal NIL. This domain of validity is composed of two uncoupled functions, one for the material properties and the mean pressure applied to the pattern, and one for the geometry considered. The latter function has been determined with numerical simulations using the natural element method. It is demonstrated that knowing the mean applied pressure, the critical shear rate, and the viscosity of the material we are able to determine, depending on stamp geometry, if shear-thinning may or may not occur during an imprinting process.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/71752013-01-01T00:00:00ZTEYSSEDRE, HubertGILORMINI, PierreLANDIS, StefanREGNIER, GillesNanoimprint lithography is an efficient way to reproduce nanostructures down to 20 nanometers in sub-micrometer polymeric films. To optimize this process, simulation using a Newtonian behavior is a cheap and efficient way to predict the polymer flow in micro and nano size cavities. This behavior is nevertheless limited to flows with shear rates below a critical value that can be determined with standard rheology measurements. We have investigated the validity domain of this behavior to simulate thermal NIL. This domain of validity is composed of two uncoupled functions, one for the material properties and the mean pressure applied to the pattern, and one for the geometry considered. The latter function has been determined with numerical simulations using the natural element method. It is demonstrated that knowing the mean applied pressure, the critical shear rate, and the viscosity of the material we are able to determine, depending on stamp geometry, if shear-thinning may or may not occur during an imprinting process.Thermoforming of a PMMA transparency near glass transition temperature
http://hdl.handle.net/10985/6684
Thermoforming of a PMMA transparency near glass transition temperature
GILORMINI, Pierre; CHEVALIER, Luc; REGNIER, Gilles
In order to simulate the thermoforming of a transparency, constitutive equations are proposed for the nonlinear viscoelastic behaviour of poly(methyl methacrylate) near glass transition temperature, which include large deformations. In a first step, they are fitted on a set of uniaxial tensionrelaxation tests at various strain levels and strain rates. In a second step, their implementation in a finite element code is performed. Finally, the thermoforming of a transparency at a constant and uniform temperature is simulated and compared with experimental results.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/66842010-01-01T00:00:00ZGILORMINI, PierreCHEVALIER, LucREGNIER, GillesIn order to simulate the thermoforming of a transparency, constitutive equations are proposed for the nonlinear viscoelastic behaviour of poly(methyl methacrylate) near glass transition temperature, which include large deformations. In a first step, they are fitted on a set of uniaxial tensionrelaxation tests at various strain levels and strain rates. In a second step, their implementation in a finite element code is performed. Finally, the thermoforming of a transparency at a constant and uniform temperature is simulated and compared with experimental results.Cyclic and monotonic testing of free and constrained recovery properties of a chemically crosslinked acrylate
http://hdl.handle.net/10985/7759
Cyclic and monotonic testing of free and constrained recovery properties of a chemically crosslinked acrylate
ARRIETA, Juan Sebastian; DIANI, Julie; GILORMINI, Pierre
A chemically crosslinked acrylate network was submitted to various thermomechanical strain and stress recoveries while changing the experimental parameters in order to better define the benefits and the limits of using chemically crosslinked polymers for multicycle applications or applications under external constraints. The results showed that the free recoveries and the constrained recoveries remained the same at the first cycle and during the next ones. It was also shown that the low stress usually generated by a crosslinked network when submitted to a constrained recovery can be significantly increased by choosing suitable experimental conditions.
The definitive version is available at http://onlinelibrary.wiley.com/doi/10.1002/app.39813/full
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/77592014-01-01T00:00:00ZARRIETA, Juan SebastianDIANI, JulieGILORMINI, PierreA chemically crosslinked acrylate network was submitted to various thermomechanical strain and stress recoveries while changing the experimental parameters in order to better define the benefits and the limits of using chemically crosslinked polymers for multicycle applications or applications under external constraints. The results showed that the free recoveries and the constrained recoveries remained the same at the first cycle and during the next ones. It was also shown that the low stress usually generated by a crosslinked network when submitted to a constrained recovery can be significantly increased by choosing suitable experimental conditions.Molecular mobility with respect to accessible volume in Monte Carlo lattice model for polymers
http://hdl.handle.net/10985/11439
Molecular mobility with respect to accessible volume in Monte Carlo lattice model for polymers
DIANI, Julie; GILORMINI, Pierre
A three-dimensional cubic Monte Carlo lattice model is considered to test the impact of volume on the molecularmobility of amorphous polymers. Assuming classic polymer chain dynamics, the concept of locked volume limiting the accessible volume around the polymer chains is introduced. The polymer mobility is assessed by its ability to explore the entire lattice thanks to reptation motions. When recording the polymer mobility with respect to the lattice accessible volume, a sharp mobility transition is observed as witnessed during glass transition. The model ability to reproduce known actual trends in terms of glass transition with respect to material parameters, is also tested.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/114392017-01-01T00:00:00ZDIANI, JulieGILORMINI, PierreA three-dimensional cubic Monte Carlo lattice model is considered to test the impact of volume on the molecularmobility of amorphous polymers. Assuming classic polymer chain dynamics, the concept of locked volume limiting the accessible volume around the polymer chains is introduced. The polymer mobility is assessed by its ability to explore the entire lattice thanks to reptation motions. When recording the polymer mobility with respect to the lattice accessible volume, a sharp mobility transition is observed as witnessed during glass transition. The model ability to reproduce known actual trends in terms of glass transition with respect to material parameters, is also tested.Influence of thermal diffusion and shear-thinning during the leveling of nanoimprinted patterns in a polystyrene thin film
http://hdl.handle.net/10985/9845
Influence of thermal diffusion and shear-thinning during the leveling of nanoimprinted patterns in a polystyrene thin film
TEYSSEDRE, Hubert; LANDIS, Stefan; GILORMINI, Pierre; REGNIER, Gilles
When capillary forces prevail, the leveling of the free surface of a fluid film is a natural phenomenon that has already found applicative interest either with brushmarks for paint coatings or for rheology on polymeric thin films. Among many parameters, the material behavior influences notably this phenomenon and its characterization still arouses curiosity at the nanoscale. In this article the nanoscale properties of a polystyrene film are derived from the leveling rate of nanoimprinted patterns and are compared to bulk values obtained with a parallel plate rheometer. In particular the focus is made on the isothermal assumption during the process and the consequences of an anisothermal state on the material behavior. Both points are investigated by using numerical simulations based on the natural element method. First we demonstrate experimentally that the leveling rate is influenced by the heat exchange at the air-polymer interface and that thermal diffusion should be taken into account within the film and its underlying substrate. Then we numerically investigate the influence of thermal diffusion and shear-thinning on the leveling rate. Finally we show that the bulk properties can represent particularly closely the behavior of the polymer at the nanoscale if adequate thermal boundary conditions are used and if shear-thinning is taken into account. This agreement postulates a decrease by 7◦C of the mean temperature of the polystyrene film coated on silicon when experiments are carried out on a hotplate at 100◦C in a cleanroom environment.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/98452015-01-01T00:00:00ZTEYSSEDRE, HubertLANDIS, StefanGILORMINI, PierreREGNIER, GillesWhen capillary forces prevail, the leveling of the free surface of a fluid film is a natural phenomenon that has already found applicative interest either with brushmarks for paint coatings or for rheology on polymeric thin films. Among many parameters, the material behavior influences notably this phenomenon and its characterization still arouses curiosity at the nanoscale. In this article the nanoscale properties of a polystyrene film are derived from the leveling rate of nanoimprinted patterns and are compared to bulk values obtained with a parallel plate rheometer. In particular the focus is made on the isothermal assumption during the process and the consequences of an anisothermal state on the material behavior. Both points are investigated by using numerical simulations based on the natural element method. First we demonstrate experimentally that the leveling rate is influenced by the heat exchange at the air-polymer interface and that thermal diffusion should be taken into account within the film and its underlying substrate. Then we numerically investigate the influence of thermal diffusion and shear-thinning on the leveling rate. Finally we show that the bulk properties can represent particularly closely the behavior of the polymer at the nanoscale if adequate thermal boundary conditions are used and if shear-thinning is taken into account. This agreement postulates a decrease by 7◦C of the mean temperature of the polystyrene film coated on silicon when experiments are carried out on a hotplate at 100◦C in a cleanroom environment.Platicizer effect on network structure and hydrolytic degradation
http://hdl.handle.net/10985/9634
Platicizer effect on network structure and hydrolytic degradation
DERUE, Isabelle; GILORMINI, Pierre; VERDU, Jacques; VAULOT, Cyril; COQUILLAT, Marie; DESGARDIN, Nancy; VANDENBROUKE, Aude; RICHAUD, Emmanuel
The hydrolytic degradation of fully cured polyester-urethane networks polymerized in the presence of several weight ratios of triacetin was monitored by the residual concentration in elastically active chains obtained from modulus and equilibrium solvent swelling measurements. The presence of triacetin does not change the water uptake but induces a lower rate of degradation. Comparisons were performed with networks in which triacetin was removed before ageing, and with networks in which polyester-urethane was first polymerized and then impregnated by triacetin. Data suggest that the presence of triacetin during polymerization induces the presence of elastically inactive chains such as dangling chains, loops… the hydrolysis of which does not change the elastic properties of the network. This explanation was checked from relaxation measurements by n.m.r and d.m.a, and by the analysis of the soluble fraction generated by hydrolysis.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/96342015-01-01T00:00:00ZDERUE, IsabelleGILORMINI, PierreVERDU, JacquesVAULOT, CyrilCOQUILLAT, MarieDESGARDIN, NancyVANDENBROUKE, AudeRICHAUD, EmmanuelThe hydrolytic degradation of fully cured polyester-urethane networks polymerized in the presence of several weight ratios of triacetin was monitored by the residual concentration in elastically active chains obtained from modulus and equilibrium solvent swelling measurements. The presence of triacetin does not change the water uptake but induces a lower rate of degradation. Comparisons were performed with networks in which triacetin was removed before ageing, and with networks in which polyester-urethane was first polymerized and then impregnated by triacetin. Data suggest that the presence of triacetin during polymerization induces the presence of elastically inactive chains such as dangling chains, loops… the hydrolysis of which does not change the elastic properties of the network. This explanation was checked from relaxation measurements by n.m.r and d.m.a, and by the analysis of the soluble fraction generated by hydrolysis.