Birefringence of plastically deformed poly(methyl methacrylate)

Raha, Sumanta; Bowden, P. B.

doi:10.1016/0032-3861(72)90042-0

Cited by 112 publications

(42 citation statements)

References 11 publications

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“…The plastic partψ p is borrowed from the non-Gaussian rubber elasticity theories where the shear modulus has a molecular interpretation μ p :=n p kθ. Following the work of Raha and Bowden [3] that is based on the thermal dissociation of the secondary bonds in the polymer network, we consider the change of the chain density n p with temperature through n p (θ) = A + B (1 − exp(−E a /Rθ)). In order to conserve mass, the number of segments in a molecule is determined by Adjustable parameters of the above introduced material model are identified by means of the homogeneous experiments in Fig.1.…”

Section: Experimental Observationsmentioning

confidence: 99%

Finite thermo‐viscoplasticity of amorphous glassy polymers: Experiments, modeling and simulations

Göktepe

Méndez

Miehé

2007

Proc Appl Math and Mech

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The contribution is concerned with experimental procedures, constitutive modeling and the numerical simulations of finite thermo-viscoplastic behavior of glassy polymers. The experimental study involves both homogeneous and inhomogeneous tests at different temperatures under isothermal conditions. The true stress-true strain curves obtained from compressive homogeneous uniaxial and plane strain experiments are employed in the identification of adjustable material parameters. In contrast to the existing kinematic approaches to finite plasticity of glassy polymers, we propose a distinct kinematic framework constructed in the logarithmic strain space. This leads us to an algorithmically very attractive, additive kinematic structure in R 6 similar to the geometrically linear theory. The proposed three-dimensional model is implemented into a finite element code. The load-displacement curves acquired from inhomogeneous experiments are compared against the results obtained from finite element analyses where the material parameters identified from homogeneous experiments are used. Experimental ObservationsThe mechanical behavior of glassy polymers is sensitive to temperature and deformation rate as commonly observed in most of the polymeric materials. True stress-true strain curves obtained from macroscopically homogeneous compressive uniaxial and plane strain experiments on polycarbonate (PC) specimens under isothermal conditions at three different temperatures and rates are depicted in Fig. 1. These stress-strain curves point out the three distinct phenomena for increasing temperature values: i) The softening in the post-yield kinematical hardening phase, ii) the drop in the yield stress and iii) the slight decrease in the amount of stress softening, see Fig.1. Increase in the mobility of macromolecules at elevated temperatures causes the material to be more prone to deform plastically. Furthermore, the material response under plane strain deformation comes out to be stiffer with regard to the yield stress and the post yield hardening. This is chiefly related to the excessive constraint conditions in the plane strain deformation compared to the uniaxial mode of deformation. It can also be readily seen that the temperature dependency of the material is more pronounced than its sensitivity to the strain rates considered in this study. In addition to the homogeneous experiments, the load-displacement diagrams acquired from tensile inhomogeneous experiments on dumbbell-shaped PC specimens are shown in Fig. 2b. These curves also reflect the temperature dependent phenomena observed in the homogeneous experiments in Fig. 1.

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Section: Experimental Observationsmentioning

confidence: 99%

Finite thermo‐viscoplasticity of amorphous glassy polymers: Experiments, modeling and simulations

Göktepe

Méndez

Miehé

2007

Proc Appl Math and Mech

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“…More recently, Jancar et al [10] studied the effect of temperature and strain rate on yield stresses and post-yield softening of PMMA. Additionally, Raha and Bowsen [11] conducted plane-strain compression tests on PMMA to study the structural changes employing birefringence measurements. They reported that the model of dissociable cohesion points gave a reasonable explanation to all the observations on the polymer for its optical and mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent mechanical behaviour of PMMA: Experimental analysis and modelling

2017

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b s t r a c tAn experimental study of temperature-dependent mechanical behaviour of Poly-methyl methacrylate (PMMA) was performed at a range of temperatures (20 C, 40 C, 60 C and 80 C) below its glass transition point (108 C) under uniaxial tension and three-point bending loading conditions. This study was accompanied by simulations aimed at identification of material parameters for two different constitutive material models. Experimental flow curves obtained for PMMA were used in elasto-plastic analysis, while a sim-flow optimization tool was employed for a two-layer viscoplasticity model. The temperature increase significantly affected mechanical behaviour of PMMA, with quasi-brittle fracture at room temperature and super-plastic behaviour (ε>110%) at 80 C. The two-layer viscoplasticity material model was found to agree better with the experimental data obtained for uniaxial tension than the elasto-plastic description.

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“…The plastic part ψ p is borrowed from the non-Gaussian rubber elasticity theories in which the shear modulus has a molecular interpretation µ p :=n p kθ. Following the work of Raha and Bowden [6] that is based on the thermal disassociation of the secondary bonds in the polymer network, we consider the change of the chain density n p in temperature n p (θ) = A + B (1 − exp(−E a /Rθ)). In order to conserve mass, the number of segments in a molecule is determined by…”

Section: Constitutive Framework and Simulationsmentioning

confidence: 99%

“…The evolution law of plastic strains is adopted from Argon's double kink theory [1,3]. Temperature-induced softening is incorporated by thermal disassociation of the secondary bonds in the polymer network [6,2]. In the FE analysis of the coupled BVPs, the staggered scheme is employed [7].…”

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confidence: 99%

Coupled Finite Thermoviscoplasticity of Glassy Polymers

Göktepe

Miehé

2006

Proc Appl Math and Mech

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The contribution is concerned with the constitutive modeling of the temperature and thermomechanical coupling effects on the rate-dependent finite plastic behavior of glassy polymers. In contrast to the existing kinematic approaches to the finite plasticity of glassy polymers, we propose a distinct kinematic framework constructed in the logarithmic strain space [5]. The logarithmic framework is extremely attractive due to the fact that it allows a very efficient algorithmic treatment of finite plasticity akin to the geometrically linear theory. The evolution law of plastic strains is adopted from Argon's double kink theory [1,3]. Temperature-induced softening is incorporated by thermal disassociation of the secondary bonds in the polymer network [6,2]. In the FE analysis of the coupled BVPs, the staggered scheme is employed [7]. The proposed formulation is validated by simulating various experimental data.

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Birefringence of plastically deformed poly(methyl methacrylate)

Cited by 112 publications

References 11 publications

Finite thermo‐viscoplasticity of amorphous glassy polymers: Experiments, modeling and simulations

Finite thermo‐viscoplasticity of amorphous glassy polymers: Experiments, modeling and simulations

Temperature-dependent mechanical behaviour of PMMA: Experimental analysis and modelling

Coupled Finite Thermoviscoplasticity of Glassy Polymers

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