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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Fri, 10 Jul 2020 00:12:54 GMT2020-07-10T00:12:54ZA torsion test for the study of the large deformation recovery of shape memory polymers
http://hdl.handle.net/10985/6560
A torsion test for the study of the large deformation recovery of shape memory polymers
DIANI, Julie; FREDY, Carole; GILORMINI, Pierre; MERCKEL, Yannick; REGNIER, Gilles; ROUSSEAU, Ingrid
A torsion device was designed and built for testing the shape fixity and shape recovery of shape memory polymers at large deformation. A simple thermal chamber was used to regulate the thermal environment during testing and a CCD camera was used for recording the deformation. Such a torsion testing system provided a quantitative estimate of the kinematics and kinetics of shape recovery for samples submitted to large deformations at moderate strains that are more likely expected in actual shape memory applications. In addition, such measurements are complementary to those obtained from large strain uniaxial tension tests usually run for during traditional shape memory effect characterization. As a result, the torsional shape memory testing device and testing method described is expected to contribute building complementary data for the thermomechanical modeling of shape memory polymers.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/65602011-01-01T00:00:00ZDIANI, JulieFREDY, CaroleGILORMINI, PierreMERCKEL, YannickREGNIER, GillesROUSSEAU, IngridA torsion device was designed and built for testing the shape fixity and shape recovery of shape memory polymers at large deformation. A simple thermal chamber was used to regulate the thermal environment during testing and a CCD camera was used for recording the deformation. Such a torsion testing system provided a quantitative estimate of the kinematics and kinetics of shape recovery for samples submitted to large deformations at moderate strains that are more likely expected in actual shape memory applications. In addition, such measurements are complementary to those obtained from large strain uniaxial tension tests usually run for during traditional shape memory effect characterization. As a result, the torsional shape memory testing device and testing method described is expected to contribute building complementary data for the thermomechanical modeling of shape memory polymers.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.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.Experimental study and numerical simulation of the vertical bounce of a polymer ball over a wide temperature range
http://hdl.handle.net/10985/7694
Experimental study and numerical simulation of the vertical bounce of a polymer ball over a wide temperature range
DIANI, Julie; GILORMINI, Pierre; AGBOBADA, Gerry
The dependence to temperature of the rebound of a solid polymer ball on a rigid slab is investigated. An acrylate polymer ball is brought to a wide range of temperatures, covering its glass to rubbery transition, and let fall on a granite slab while the coe cient of restitution, duration of contact, and force history are measured experimentally. The ball fabrication is controlled in the lab, allowing the mechanical characterization of the material by classic dynamic mechanical analysis (DMA). Finite element simulations of the rebound at various temperatures are run, consider- ing the material as viscoelatic and as satisfying a WLF equation for its time-temperature superposition property. A comparison between the experiments and the simulations shows the strong link between viscoelasticity and time-temperature superposition properties of the material and the bounce characteristics of the ball.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/76942014-01-01T00:00:00ZDIANI, JulieGILORMINI, PierreAGBOBADA, GerryThe dependence to temperature of the rebound of a solid polymer ball on a rigid slab is investigated. An acrylate polymer ball is brought to a wide range of temperatures, covering its glass to rubbery transition, and let fall on a granite slab while the coe cient of restitution, duration of contact, and force history are measured experimentally. The ball fabrication is controlled in the lab, allowing the mechanical characterization of the material by classic dynamic mechanical analysis (DMA). Finite element simulations of the rebound at various temperatures are run, consider- ing the material as viscoelatic and as satisfying a WLF equation for its time-temperature superposition property. A comparison between the experiments and the simulations shows the strong link between viscoelasticity and time-temperature superposition properties of the material and the bounce characteristics of the ball.Extension of the natural element method to surface tension and wettability for the simulation of polymer flows at the micro and nano scales
http://hdl.handle.net/10985/7294
Extension of the natural element method to surface tension and wettability for the simulation of polymer flows at the micro and nano scales
TEYSSEDRE, Hubert; GILORMINI, Pierre
The natural element method is used to simulate two-dimensional viscous flows where interfacial effects must be taken into account, for application to polymer melts at the micro and nano scales. The variational formulation includes surface tension on the free surfaces, a net wetting force is applied at the contact line where the fluid reaches a solid surface, and the Navier-slip condition is used along fluid-solid interfaces. No dynamic wetting angle is prescribed, and the contact angle obtained results from the other material parameters and from overall flow conditions. A comparison with an analytical solution in a simple surface tension-driven flow is given, and contact with a rigid solid is involved in the transient spreading of a droplet and in the steady movement of a meniscus between two plates.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/72942013-01-01T00:00:00ZTEYSSEDRE, HubertGILORMINI, PierreThe natural element method is used to simulate two-dimensional viscous flows where interfacial effects must be taken into account, for application to polymer melts at the micro and nano scales. The variational formulation includes surface tension on the free surfaces, a net wetting force is applied at the contact line where the fluid reaches a solid surface, and the Navier-slip condition is used along fluid-solid interfaces. No dynamic wetting angle is prescribed, and the contact angle obtained results from the other material parameters and from overall flow conditions. A comparison with an analytical solution in a simple surface tension-driven flow is given, and contact with a rigid solid is involved in the transient spreading of a droplet and in the steady movement of a meniscus between two plates.Radiochemical 'degelation' of polymethyl methacrylate networks
http://hdl.handle.net/10985/11494
Radiochemical 'degelation' of polymethyl methacrylate networks
GILORMINI, Pierre; RICHAUD, Emmanuel; VERDU, Jacques
Methyl methacrylate-ethylene glycol dimethacrylate networks were synthetized and submitted to radiochemical degradation, with ageing monitored by means of sol-gel analysis. The networks were shown to undergo chain scission predominantly, which leads to their degelation, i.e., the recovery of a thermoplastic-like behavior with loss of all elastically active chains. The degelation dose was shown to increase with crosslink density and the corresponding critical conversion ratio was discussed regarding a recent and general statistical theory that covers radiochemical as well as chemical chain scissions.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/114942017-01-01T00:00:00ZGILORMINI, PierreRICHAUD, EmmanuelVERDU, JacquesMethyl methacrylate-ethylene glycol dimethacrylate networks were synthetized and submitted to radiochemical degradation, with ageing monitored by means of sol-gel analysis. The networks were shown to undergo chain scission predominantly, which leads to their degelation, i.e., the recovery of a thermoplastic-like behavior with loss of all elastically active chains. The degelation dose was shown to increase with crosslink density and the corresponding critical conversion ratio was discussed regarding a recent and general statistical theory that covers radiochemical as well as chemical chain scissions.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.On the role of hydrogen bonding on water absorption in polymers
http://hdl.handle.net/10985/12814
On the role of hydrogen bonding on water absorption in polymers
GILORMINI, Pierre; VERDU, Jacques
A kinetic model is proposed for the absorption of water in polymers. The process of bonding-debonding water molecules is described by two opposite reactions with different rate constants, and the key role of the concentration of traps by hydrogen bonding in the polymer matrix is highlighted. These three parameters are combined such that an equation is obtained that generalizes the model proposed by Carter and Kibler, with an additional, crossed, term. Numerical application is performed for the diffusion-absorption of water in a plane polymer sheet, and the parameter ranges where a quasi-Fickian water uptake curve is obtained are defined. The associated apparent diffusivity is shown to obey a hyperbolic variation with equilibrium water uptake for homologous series of polymers, which is in agreement with previous experimental observations.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/128142018-01-01T00:00:00ZGILORMINI, PierreVERDU, JacquesA kinetic model is proposed for the absorption of water in polymers. The process of bonding-debonding water molecules is described by two opposite reactions with different rate constants, and the key role of the concentration of traps by hydrogen bonding in the polymer matrix is highlighted. These three parameters are combined such that an equation is obtained that generalizes the model proposed by Carter and Kibler, with an additional, crossed, term. Numerical application is performed for the diffusion-absorption of water in a plane polymer sheet, and the parameter ranges where a quasi-Fickian water uptake curve is obtained are defined. The associated apparent diffusivity is shown to obey a hyperbolic variation with equilibrium water uptake for homologous series of polymers, which is in agreement with previous experimental observations.On necessary precautions when measuring solid polymer linear viscoelasticity with dynamic analysis in torsion
http://hdl.handle.net/10985/12466
On necessary precautions when measuring solid polymer linear viscoelasticity with dynamic analysis in torsion
DIANI, Julie; GILORMINI, Pierre
Solid polymer linear viscoelasticity in shear is often characterized by applying torsion and using the Saint-Venant solution when rectangular prismatic specimens are considered. It is shown that experimental dynamic torsion tests can show a dependency of the storage modulus and damping factor on the dimensions of the rectangular prismatic specimen when linear temperature ramps are applied. While the discrepancy of damping factor is explained by temperature heterogeneities and can be corrected easily by applying temperature steps, the inconsistency of storage modulus is due to an invalid application of the Saint-Venant solution. Finite element simulations allowed definition of the sample dimensions for which the Saint-Venant solution provides a good approximation, and a coefficient is given to correct the results obtained with commercial rheometers when other sample dimensions are used.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/124662017-01-01T00:00:00ZDIANI, JulieGILORMINI, PierreSolid polymer linear viscoelasticity in shear is often characterized by applying torsion and using the Saint-Venant solution when rectangular prismatic specimens are considered. It is shown that experimental dynamic torsion tests can show a dependency of the storage modulus and damping factor on the dimensions of the rectangular prismatic specimen when linear temperature ramps are applied. While the discrepancy of damping factor is explained by temperature heterogeneities and can be corrected easily by applying temperature steps, the inconsistency of storage modulus is due to an invalid application of the Saint-Venant solution. Finite element simulations allowed definition of the sample dimensions for which the Saint-Venant solution provides a good approximation, and a coefficient is given to correct the results obtained with commercial rheometers when other sample dimensions are used.Comparison of several closure approximations for evaluating the thermoelastic properties of an injection molded short-fiber composite
http://hdl.handle.net/10985/6676
Comparison of several closure approximations for evaluating the thermoelastic properties of an injection molded short-fiber composite
DRAY, Delphine; GILORMINI, Pierre; REGNIER, Gilles
The accurate prediction of both the elastic properties and the thermal expansion coefficients is very important for the precise simulation of such processes as injection molding of short-fiber polymer-matrix composites. In this work, a two-step homogenization procedure is applied and compared with experimental values obtained on a polyarylamide/glass fiber composite for a broad range of temperatures. It is observed that the stiffness averaging version of the model surpasses the compliance averaging variant, especially when it is combined with a precise evaluation of the fourth-order orientation tensor. It is also demonstrated that the orthotropic closure approximations are significantly better than previous ones (linear, quadratic, and hybrid) and than a very recent one. Among the orthotropic closure approximations, the fitted ones lead to acceptable results, which are very close to those obtained with the experimentally measured fourth-order orientation tensor.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/10985/66762007-01-01T00:00:00ZDRAY, DelphineGILORMINI, PierreREGNIER, GillesThe accurate prediction of both the elastic properties and the thermal expansion coefficients is very important for the precise simulation of such processes as injection molding of short-fiber polymer-matrix composites. In this work, a two-step homogenization procedure is applied and compared with experimental values obtained on a polyarylamide/glass fiber composite for a broad range of temperatures. It is observed that the stiffness averaging version of the model surpasses the compliance averaging variant, especially when it is combined with a precise evaluation of the fourth-order orientation tensor. It is also demonstrated that the orthotropic closure approximations are significantly better than previous ones (linear, quadratic, and hybrid) and than a very recent one. Among the orthotropic closure approximations, the fitted ones lead to acceptable results, which are very close to those obtained with the experimentally measured fourth-order orientation tensor.