Bulk modulus evolution of thermoset resins during crosslinking: Is a direct and accurate measurement possible?

Péron, Mael; Sobotka, Vincent; Boyard, Nicolas; Corre, Steven Le

doi:10.1177/0021998316647119

Cited by 11 publications

(9 citation statements)

References 29 publications

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“…Overall, the bulk modulus demonstrates a low sensitivity to crosslinking density, particularly at higher degrees of crosslinking. There is a maximum 25% difference between 50% degree of curing and a fully cured sample [ 29 ].…”

Section: Resultsmentioning

confidence: 99%

United-Atom Molecular Dynamics Study of the Mechanical and Thermomechanical Properties of an Industrial Epoxy

et al. 2021

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Epoxy resins are the most commonly used adhesives in industry due to their versatility, low cost, low toxicity, low shrinkage, high strength, resistance to moisture, and effective electrical resistance. These diverse properties can be tailored based on the chemical structure of the curing agent and the conditions of the curing process. Molecular simulations of epoxy resins have gained attention in recent years as a means to navigate the vast choice of chemical agents and conditions that will give the required properties of the resin. This work examines the statistical uncertainty in predicting thermodynamic and mechanical properties of an industrial epoxy resin using united atom molecular dynamics simulation. The results are compared with experimental measurements of the elastic modulus, Poisson’s ratio, and the glass transition temperature obtained at different temperatures and degrees of curing. The decreasing trend of the elastic modulus with increasing temperature is accurately captured by the simulated model, though the uncertainty in the calculated average is large. The glass transition temperature is expectedly overpredicted due to the high rates accessible to molecular simulations. We find that Poisson’s ratio is particularly sensitive to sample anisotropy as well as the method of evaluation, which explains the lack of consistent trends previously observed with molecular simulation at different degrees of crosslinking and temperatures.

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Section: Resultsmentioning

confidence: 99%

United-Atom Molecular Dynamics Study of the Mechanical and Thermomechanical Properties of an Industrial Epoxy

et al. 2021

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“…Experiments performed under higher pressure levels should be preferred in the future, as was already demonstrated on another plunger-type volumetric dilatometer developed by the same research team. 41 To counteract this limitation, an interpolation function is proposed (equation (11)), which is based on the results from PvT-XT measurements when the temperature is higher than T g and on values from literature for lower temperatures. As the values before and after crystallization are close, it is considered that the crystallization does not affect the value of K m .…”

Section: Experimental Characterizationmentioning

confidence: 99%

Thermomechanical characterization of a low viscosity PA66 thermoplastic matrix and associated continuous glass fibre composite under processing conditions

Péron

Jacquemin

Casari

et al. 2019

Journal of Composite Materials

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Characterizing the thermomechanical properties of thermoplastic resins and associated composites is of outmost importance to understand the development of process-induced stresses. To that extent, the characterization of a low viscosity PA66 matrix is proposed thanks to a homemade volumetric dilatometer named PvT-XT and a dynamic mechanical analyser on a wide temperature range. The PvT-XT results, reported for the first time, permit to identify the evolution of the coefficients of thermal expansion, of crystallization shrinkage and of the bulk modulus with temperature. Dynamic mechanical analyser experiments lead to the estimation of the Young’s modulus. The shear modulus as well as the Poisson’s ratio are then estimated thanks to analytical relations for isotropic and homogeneous materials. These properties are used to feed a new analytical model estimating the coefficients of thermal expansion of quasi-unidirectional composites. All the results are compared with the values from the literature or from complementary experiments, showing a good agreement which permits to validate the developed methodology.

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“…This model relates the curing state in the material with the time and temperature evolution. Currently, several works can be found in the literature regarding the experimental characterization of the curing behavior of polymeric resins, including epoxies [13][14][15][16][17][18][19][20]. Many of them use differential scanning calorimetry (DSC) and dynamical mechanical analysis (DMA) to identify the curing behavior and the evolution of the elastic modulus.…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Micro-Residual Stresses in a Carbon/Epoxy Polymer Matrix Composite during Curing Process

et al. 2022

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The manufacturing process in thermoset-based carbon fiber-reinforced polymers (CFRPs) usually requires a curing stage where the material is transformed from a gel state to a monolithic solid state. During the curing process, micro-residual stresses are developed in the material due to the different chemical–thermal–mechanical properties of the fiber and of the polymer, reducing the mechanical performance of the composite material compared to the nominal performance. In this study, computational micromechanics is used to analyze the micro-residual stresses development and to predict its influence on the mechanical performance of a pre-impregnated unidirectional CFRP made of T700-fibers and an aeronautical grade epoxy. The numerical model of a representative volume element (RVE) was developed in the commercial software Abaqus® and user-subroutines are used to simulate the thermo-curing process coupled with the mechanical constitutive model. Experimental characterization of the bulk resin properties and curing behavior was made to setup the models. The higher micro-residual stresses occur at the thinner fiber gaps, acting as triggers to failure propagation during mechanical loading. These micro-residual stresses achieve peak values above the yield stress of the resin 55 MPa, but without achieving damage. These micro-residual stresses reduce the transverse strength by at least 10%, while the elastic properties remain almost unaffected. The numerical results of the effective properties show a good agreement with the macro-scale experimentally measured properties at coupon level, including transverse tensile, longitudinal shear and transverse shear moduli and strengths, and minor in-plane and transverse Poisson’s ratios. A sensitivity analysis was performed on the thermal expansion coefficient, chemical shrinkage, resin elastic modulus and cure temperature. All these parameters change the micro-residual stress levels and reduce the strength properties.

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Bulk modulus evolution of thermoset resins during crosslinking: Is a direct and accurate measurement possible?

Cited by 11 publications

References 29 publications

United-Atom Molecular Dynamics Study of the Mechanical and Thermomechanical Properties of an Industrial Epoxy

United-Atom Molecular Dynamics Study of the Mechanical and Thermomechanical Properties of an Industrial Epoxy

Thermomechanical characterization of a low viscosity PA66 thermoplastic matrix and associated continuous glass fibre composite under processing conditions

Numerical Analysis of Micro-Residual Stresses in a Carbon/Epoxy Polymer Matrix Composite during Curing Process

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