Moisture transport in PA6 and its influence on the mechanical properties

Sharma, Prateek; Sambale, Anna Katharina; Stommel, Markus; Maisl, Michael; Herrmann, Hans–Georg; Diebels, Stefan

doi:10.1007/s00161-019-00815-w

Cited by 15 publications

(29 citation statements)

References 39 publications

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“…A short introduction of the modelling approach for the material behaviour and moisture uptake kinetics is given here. For a more detailed explanation the readers can refer to Sharma et al [21].…”

Section: Modellingmentioning

confidence: 99%

“…can be done. The interpolation in [21] was done with a sigmoid function, fit with the help of just three points, which was not ideal. The change in the material properties happen because of a phase change from a glassy to rubbery phase.…”

Section: Coupling Mechanical Stiffnesses To the Concentrationmentioning

confidence: 99%

“…One of the effects of the phase transition is that the stiffness of the material decreases which has been seen in experimental results [6,7,11]. Many authors have modelled this behaviour with the help of dependency of material parameters on the concentration [3,12,14,15,18,21]. There is also a change in the viscoelastic relaxation behaviour with the phase transition, which has been captured by interpolating the relaxation times between the dry and saturated specimen to an effective relaxation time [14,21].…”

Section: Introductionmentioning

confidence: 99%

“…Many authors have modelled this behaviour with the help of dependency of material parameters on the concentration [3,12,14,15,18,21]. There is also a change in the viscoelastic relaxation behaviour with the phase transition, which has been captured by interpolating the relaxation times between the dry and saturated specimen to an effective relaxation time [14,21]. Further, the coupling of the diffusion model on the mechanical loading has been done by making the diffusion coefficient a function of the strain values [3,15].…”

Section: Introductionmentioning

confidence: 99%

“…Hence a coupling of the diffusion coefficient to the strain is not a correct modelling approach. The model presented by the authors [21] with one sided coupling, where the moisture concentration affects the mechanical properties was to be validated with 3-point-bending tests. The results from the experiment however showed deviation from the simulation, which indicates that a moisture redistribution does take place due to the loading.…”

Section: Introductionmentioning

confidence: 99%

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Moisture Transport In Polyamide (PA6) and Its Effect On the Mechanical Behaviour

Sharma¹,

Diebels²

2021

14th WCCM-ECCOMAS Congress

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Polyamide exhibits hygroscopic nature and can absorb up to 10 % of moisture relative to its weight. The absorbed moisture increases the mobility of the molecular chains and causes a reduction in the glass transition temperature. Thus, depending on the moisture distribution, a polyamide component can show different stiffness and relaxation times. The moisture distribution also depends on the mechanical loading of the material. However, it was noticed that the diffusion process remains unaffected when the process is compared for a loaded and an unloaded material. It is postulated that the moisture redistribution is due to an external force that takes place as a result of the pressure acting on the moisture. The diffusion process is unaffected by preloading of the dry material as the pressure is applied purely on the material and not on the absorbed moisture. However, when a saturated specimen is loaded, the pressure is exerted on the moisture too which causes its redistribution. In this work, the distribution of the absorbed moisture is simulated by a non-linear diffusion model. It is coupled with the viscoelastic behaviour of PA6. The stiffness of the viscoelastic model changes and the relaxation time reduces with increasing moisture concentration. The coupling of diffusion to mechanical loading is achieved with the recalculation of the moisture concentration caused due to the redistribution of volume. It is assumed that there is no transport of moisture, but the transport of volume and the change in volume creates a change in concentration in the specimen. This strongly coupled model has been implemented using the finite element method. The model results are compared to experiments for validation. A strongly coupled model was thus created which could reproduce the experimental results with reasonable accuracy.

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Section: Modellingmentioning

confidence: 99%

Section: Coupling Mechanical Stiffnesses To the Concentrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Moisture Transport In Polyamide (PA6) and Its Effect On the Mechanical Behaviour

Sharma¹,

Diebels²

2021

14th WCCM-ECCOMAS Congress

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Characterization and model‐based mechanical analysis of moisture gradients in PA 6

Sambale

Stanko

Uhlig

et al. 2023

J of Applied Polymer Sci

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In this contribution, a numerical calculation environment for the determination of the moisture absorption of polyamide 6 (PA 6) is developed. The focus in this context is on modeling and evaluating the influence of locally varying water concentrations and existing moisture gradients on the mechanical properties of the material. Defined moisture distributions are set by specific conditioning processes and compared to the results of an FE calculation environment. The developed numerical method combines a mass diffusion with a subsequent structural‐mechanical simulation. The first includes a transient analysis of moisture absorption and the resulting swelling processes and residual stresses. The water concentration and residual stress distributions determined within this calculation are implemented as initial conditions in the structural mechanics FE analysis. The experimental setup of the three‐point bending test is considered in this case. The evaluation of the moisture‐induced influence on the mechanical behavior of the considered PA 6 is performed using a linear elastic modeling approach. The validation and evaluation of the calculation quality is carried out for the sorption and swelling calculation as well as for the FE model by means of experimental test data. The calculation methodology presented in this work provides a novel and even more accurate approach for the design of plastic components which are exposed to the influence of environmental humidity or direct water contact in their application.

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A mixture theory for the moisture transport in polyamide

Sharma¹,

Diebels²

2021

Continuum Mech. Thermodyn.

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Polyamide exhibits hygroscopic nature and can absorb up to 10% of moisture relative to its dry weight. The absorbed moisture increases the mobility of the molecular chains and causes a reduction in the glass transition temperature. Thus, depending on the moisture distribution, a polyamide component can show different stiffness and relaxation times. Moreover, the moisture distribution also depends on the mechanical loading of the material as the volumetric deformation results in a change of the available free volume for the moisture. Thus, a strongly coupled model is required to describe the material behaviour. In this work, a thermodynamically consistent coupled model within the framework of mixture theory is developed. The mechanical deformation of polyamide 6 (PA6) is based on a linear viscoelastic material model, and the moisture transport is based on a nonlinear diffusion model. The stiffness and the relaxation time of the viscoelastic model change with the moisture concentration. Furthermore, the moisture transport is affected by the pressure gradient generated by the mechanical loading of the material. This strongly coupled model has been implemented using the finite element method, and simulation results are presented for a three-point bending experiment.

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Moisture transport in PA6 and its influence on the mechanical properties

Cited by 15 publications

References 39 publications

Moisture Transport In Polyamide (PA6) and Its Effect On the Mechanical Behaviour

Moisture Transport In Polyamide (PA6) and Its Effect On the Mechanical Behaviour

Characterization and model‐based mechanical analysis of moisture gradients in PA 6

A mixture theory for the moisture transport in polyamide

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