Hygrothermal viscoelastic material characterisation of unidirectional continuous carbon-fibre reinforced polyamide 6

Dijk, Y. L.M. van; Grätzl, Thomas; Abouhamzeh, M.; Kroll, Lothar; Shroff, Sonell

doi:10.1016/j.compositesb.2018.05.054

Cited by 13 publications

(2 citation statements)

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“…Stress relaxation is a common phenomenon in polymer composite materials and the rate of relaxation can be affected by time, temperature, initial strain, environment, and so on [1][2][3][4]. In the course of long-term service, a pre-stressed part in a structure may lose its prescribed initial stress due to stress relaxation, and structural failure may occur when the retained stressed is less than the threshold value [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

An Engineering Prediction Model for Stress Relaxation of Polymer Composites at Multiple Temperatures

et al. 2022

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This study develops an engineering prediction model for stress relaxation of polymer composites, allowing the prediction of stress relaxation behaviour under a constant strain, over a range of temperatures. The model is based on the basic assumption that in the stress relaxation process the reversible strain is transformed to irreversible strain continuously. A strain-hardening model is proposed to incorporate nonlinear elastic behaviour, and a creep rate model is used to describe the irreversible deformation in the process. By using stress relaxation data at different temperatures, under different strains, the dependence on temperature and initial strain of the model parameters can be established. The effectiveness of the proposed model is verified and validated using three polymer composite materials. The performance of the model is compared with three commonly used stress relaxation models such as the parallel Maxwell and Prony series models. To ease the use of the proposed model in realistic structural problems, a user subroutine is developed, and the stress relaxation of a plate structure example is demonstrated.

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Section: Introductionmentioning

confidence: 99%

An Engineering Prediction Model for Stress Relaxation of Polymer Composites at Multiple Temperatures

et al. 2022

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“…The first theoretical model of diffusion was developed by Fick for 1D systems

J = - D \frac{\partial c}{\partial x}

where J is the solute flux per unit area (mole m −2 s −1 ), D is the diffusion coefficient of the analyzed specie (m 2 s −1 ), c is its molar concentration (mole m −3 ), x the spatial coordinate (m) and

\frac{\partial c}{\partial x}

, the concentration gradient along x (mole m −4 ). The diffusion coefficient D often depends on the temperature, according to the Arrhenius law …”

Section: Introductionmentioning

confidence: 99%

Mathematical Modeling and Experimental Study of Water Diffusion and Swelling in Polymer Films

Gagliardi

2019

Macro Theory & Simulations

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Equation (1) is also applied to solvent diffusion in polymers but more recent studies have demonstrated different diffusive behaviors for imbibition. Due to effects of polymer physical properties and polymer/solvent interactions, Alfrey and coworkers have proposed a semi-empirical classification based on polymer relaxation rates, [6] identifying the Fickian and the non-Fickian regimes. According to this model, the amount of solvent absorbed by a polymer membrane follows a power law and the power exponent is related to the transport mechanism.The transport mechanism is related to the bulk properties of the polymer, in particular the physical state. In the rubbery state, when the glass transition temperature T g is above the working temperature T w , molecules show high mobility and it facilitates solvent penetration across the polymer matrix. On the other hand, glassy polymers, with T g < T w , are more rigid and solvent absorption is less easy. [7] In some polymers, the glassy-to-rubbery transition is physically similar to that occurring in hydrated matrices. Water acts like a plasticizer and affects diffusion properties within the polymer. This plasticizer effect leads to nonlinear diffusion, and the diffusion coefficient D can show a dependency on concentration. [8] The identification of the interface between swollen and unswollen regions, and its evolution with time, can help in the evaluation of nonlinear diffusion effects. This internal boundary was experimentally tracked in gelatin beads, and its evolution with time significantly differed from that of the external bead boundary. [9] Mathematical models involving the movement of the internal boundary were developed in food science to study grain hydration [10] while in polymer membranes this study was simplified with a front-fixing transformation [11] and a comprehensive analysis of this aspect is still lacking.When soft materials imbibe a large amount of water their volume can increase. The swelling phenomenon is a kinetic process and it involves mass transport and mechanical properties. [12] In systems with variable volume, concentration profiles are described with the more advanced advection-diffusion model [13] that takes the moving front velocity v into accountNumerical models of swelling, in which the boundary of the domain needs to be calculated as part of the solution, are commonly called Stefan problems. The Stefan problem can describe Absorption Water diffusion and swelling of polymer films can be modeled by nonlinear diffusion equations with fixed or moving boundaries, investigating the Fick and the Stefan problems. To form a better view of the dynamics of the problems, this paper reports the mathematical modeling of water diffusion with linear and nonlinear diffusion coefficients by using the finite element method, and the description of boundary movements calculated with a fully implicit upwind scheme. Experimental results are used to support theoretical data. It is found that porosity strongly affects diffusion properties and proposed models de...

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The effects of temperature and hygrothermal aging on the properties of CF/PA6 composite and its compression failure mechanisms

Yu,

Xiao,

Xie

et al. 2024

Polymer Composites

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Carbon fiber reinforced polyamide composites have outstanding properties, but their applications are significantly affected by the service environment. This work evaluates the effects of temperature (25, 80, 140, and 200°C) and hygrothermal conditions on the mechanical properties of CF/PA6 composite containing delamination damage, and studies its damage behaviors and failure mechanisms. After hygrothermal aging, recrystallization of PA6 improves the heat resistance of CF/PA6 composites, but water absorption reduces the interfacial strength of composites, resulting in the decrease of modulus and compressive strength (24% and 42%, respectively). With the increase in temperature, the compressive strength of CF/PA6 composites gradually decreases (from 132 MPa at 25°C to 24 MPa at 200°C), and the failure mode transitions from fiber fractures, interlayer shear fractures, delamination to kinking. In addition, the compressive failure process of CF/PA6 composites is divided into three stages: buckling, delamination bulging and kinking failure.Highlights Hygrothermal aging reduces the fiber/resin interface performance. Fiber fracture, interlayer shear and delamination convert to kinking failure. The failure process is divided into buckling, delamination and kinking.

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Hygrothermal viscoelastic material characterisation of unidirectional continuous carbon-fibre reinforced polyamide 6

Cited by 13 publications

References 38 publications

An Engineering Prediction Model for Stress Relaxation of Polymer Composites at Multiple Temperatures

An Engineering Prediction Model for Stress Relaxation of Polymer Composites at Multiple Temperatures

Mathematical Modeling and Experimental Study of Water Diffusion and Swelling in Polymer Films

The effects of temperature and hygrothermal aging on the properties of CF/PA6 composite and its compression failure mechanisms

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