A new constitutive equation for the long-term creep of polymers based on physical aging

Zheng, Shanfu; Weng, George J.

doi:10.1016/s0997-7538(02)01215-9

Cited by 24 publications

(14 citation statements)

References 16 publications

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“…The three stages of creep have been well studied and occur for many materials and rock types (Scholz, 1968;Borchert et al 1984;Goodman, 1980;Ottosen, 1986;Zheng and Weng, 2002). …”

Section: Time-dependent Modelsmentioning

confidence: 99%

The three stages of stress relaxation - Observations for the time-dependent behaviour of brittle rocks based on laboratory testing

Paraskevopoulou

Perras

Diederichs

et al. 2017

Engineering Geology

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“…The three stages of creep have been well studied and occur for many materials and rock types (Scholz, 1968;Borchert et al 1984;Goodman, 1980;Ottosen, 1986;Zheng and Weng, 2002). …”

Section: Time-dependent Modelsmentioning

confidence: 99%

The three stages of stress relaxation - Observations for the time-dependent behaviour of brittle rocks based on laboratory testing

Paraskevopoulou

Perras

Diederichs

et al. 2017

Engineering Geology

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“…The framework of 'momentary' time approach was adopted by subsequent studies that attempted to predict long time behavior of variety of different amorphous polymeric materials, semicrystalline polymers, polymer composites, polymers with different thermal histories, etc. (Arnold and White 1995, Bradshaw and Brinson 1997, Guo and Bradshaw 2009, Guo et al 2009, Nicholson et al 2000, Read et al 1990, Tomlins et al 1994, Zheng and Weng 2002. Effect of temperature and deformation field on relaxation time and its variation as a function of time led to the time -aging time -temperature and time -aging time -stress/strain superpositions (Dorigato et al 2010, Guo and Bradshaw 2009, Jazouli et al 2005, Kolařík 2003, Kolarik and Pegoretti 2006, O'Connell and McKenna 1997, O'Connell and McKenna 2002, Schoeberle et al 2008, Shi et al 2005, Struik 1978).…”

Section: Introductionmentioning

confidence: 99%

“…Both these effects contribute to the degree of difficulty in making the prediction of long time behavior. , Nicholson et al 2000, Read et al 1990, Tomlins et al 1994, Zheng and Weng 2002 (Struik 1978) and by Read and Tomlins (Read and Tomlins 1997). We also apply time -temperature superposition and time stress superposition in the effective time domain to Struik's data.…”

mentioning

confidence: 99%

Long time response of aging glassy polymers

Joshi

2014

Rheol Acta

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Abstract:Aging amorphous polymeric materials undergo free volume relaxation, which causes slowing down of the relaxation dynamics as a function of time.The resulting time dependency poses difficulties in predicting their long time physical behavior. In this work, we apply effective time domain approach to the experimental data on aging amorphous polymers and demonstrate that it enables prediction of long time behavior over the extraordinary time scales. We demonstrate that, unlike the conventional methods, the proposed effective time domain approach can account for physical aging that occurs over the duration of the experiments. Furthermore, this procedure successfully describes timetemperature superposition and time -stress superposition. It can also allow incorporation of varying dependences of relaxation time on aging time as well as complicated but known deformation history in the same experiments. This work strongly suggests that the effective time domain approach can act as an important tool to analyze the long time physical behavior of aging amorphous polymeric materials. | P a g e I Introduction:Glassy materials such as amorphous polymers (Hodge 1995), colloidal glasses and gels (Fielding et al. 2000), spin glasses (Rodriguez et al. 2003) are usually time dependent materials owing to thermodynamically out of equilibrium state they are arrested in. Typically specific volume (and specific entropy/enthalpy) associated with an amorphous polymer is in excess compared to its equilibrium value (Donth 2001, Larson 1999, Struik 1978.Inherent tendency of any material to achieve equilibrium initiates structural rearrangement in the amorphous polymeric compounds so as to cause relaxation of specific volume (accompanied by decrease in specific entropy/enthalpy) as a function of time (Callen 1985, Struik 1978. This phenomenon is addressed in the literature as physical aging (Hodge 1995). In polymeric glasses, while taking the material closer to the equilibrium state, physical aging manifests itself by causing enhancement in relaxation time and stiffness as a function of time (Struik 1978). This time dependency continuously changes the material response to the external stimuli such as application of deformation field (stress field or strain field), electric field, etc.Consequently, a priory prediction of the long time behavior of the response function becomes a challenging task. In this work we employ the so called effective time domain approach, which allows direct prediction of long time material response of amorphous polymers by carrying out tests over the practical timescales. | P a g eThe amorphous polymeric materials when quenched rapidly from the molten state undergo glass transition (McKenna 1994). Physical aging initiates in the material subsequent thermal quench (Hodge 1995). The time elapsed since thermal quench is typically known as the aging time or the waiting time.If the material is deformed during this annealing period, response functions (such as creep compliance and relaxation modulus, depending upon ...

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“…While polyamides or polyethylene are most commonly used, they should be replaced by polyesters for obtaining higher temperature and fatigue resistance because of the stiffening action of the aromatic phenylene group. [9]. Fibre-Reinforced-Polymer composites are used particularly in the automotive and aircraft industries and the manufacture of spaceships and sea vehicles.…”

Section: Introductionmentioning

confidence: 99%

Tribological Properties of Polyester Composites: Effect of Vegetable Oils and Polymer Fibers

Ahmed¹,

Yousry²

2012

Polyester

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A new constitutive equation for the long-term creep of polymers based on physical aging

Cited by 24 publications

References 16 publications

The three stages of stress relaxation - Observations for the time-dependent behaviour of brittle rocks based on laboratory testing

The three stages of stress relaxation - Observations for the time-dependent behaviour of brittle rocks based on laboratory testing

Long time response of aging glassy polymers

Tribological Properties of Polyester Composites: Effect of Vegetable Oils and Polymer Fibers

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