The Experts below are selected from a list of 8073 Experts worldwide ranked by ideXlab platform

Christelle Delaite - One of the best experts on this subject based on the ideXlab platform.

  • ethylene vinyl acetate copolymer aluminium trihydroxide composites a new method to predict the barrier effect during cone calorimeter tests
    Polymer Degradation and Stability, 2015
    Co-Authors: Florian Cavodeau, Josemarie Lopezcuesta, Belkacem Otazaghine, Rodolphe Sonnier, Christelle Delaite
    Abstract:

    Abstract This study presents the use of oedometric compression test in order to evaluate the breakdown of a protective Layer acting as a diffusion barrier (“barrier effect”) occurring during cone calorimeter tests for ethylene-vinyl acetate copolymer/aluminium trihydroxide (EVA/ATH) composites. The formation of an alumina Layer at the sample surface during burning insulates thermally the underlying material and reduces the heat release rate. The efficiency of this barrier depends on the cohesion of the Layer formed. This cohesion depends on the ability of the particles (ATH and synergistic mineral fillers) to self-arrange. During the test, the breakdown of this barrier can lead to an increase in HRR. The oedometric compression test allows assessing the ability of fillers to form a Cohesive Layer. Results obtained from compression modulus of filler powders are directly related to some aspects of the heat release rate curve of composites measured in cone calorimeter tests. Indeed, the appearance and the intensity of the second pHRR (related to the breakdown of the barrier Layer) in cone calorimeter test are related to the slope of oedometric compression curve.

  • Ethylene-vinyl acetate copolymer/aluminium trihydroxide composites: A new method to predict the barrier effect during cone calorimeter tests
    POLYMER DEGRADATION AND STABILITY, 2015
    Co-Authors: Florian Cavodeau, Belkacem Otazaghine, Rodolphe Sonnier, Jose-marie Lopez-cuesta, Christelle Delaite
    Abstract:

    This study presents the use of oedometric compression test in order to evaluate the breakdown of a protective Layer acting as a diffusion barrier (''barrier effect'') occurring during cone calorimeter tests for ethylene-vinyl acetate copolymer/aluminium trihydroxide (EVA/ATH) composites. The formation of an alumina Layer at the sample surface during burning insulates thermally the underlying material and reduces the heat release rate. The efficiency of this barrier depends on the cohesion of the Layer formed. This cohesion depends on the ability of the particles (ATH and synergistic mineral fillers) to self-arrange. During the test, the breakdown of this barrier can lead to an increase in HRR. The oedometric compression test allows assessing the ability of fillers to form a Cohesive Layer. Results obtained from compression modulus of filler powders are directly related to some aspects of the heat release rate curve of composites measured in cone calorimeter tests. Indeed, the appearance and the intensity of the second pHRR (related to the breakdown of the barrier Layer) in cone calorimeter test are related to the slope of oedometric compression curve.

Samit Roy - One of the best experts on this subject based on the ideXlab platform.

  • A Multi-Scale Viscoelastic Cohesive Layer Model for Predicting Delamination in HTPMC
    Volume 1: Advances in Aerospace Technology, 2014
    Co-Authors: Samit Roy, Priyank Upadhyaya, Mohammad H. Haque
    Abstract:

    In this paper, a novel numerical-experimental methodology is outlined to predict delamination in pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic Cohesive Layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. This unified model is fully rate-dependent and does not require a pre-assigned traction-separation law. The actual shape of traction separation law depends on: (a) the strain rate via the viscoelastic constitutive relationship, (b) the degree of thermo-oxidative aging via the changes in the experimentally measured creep compliance due to oxidation, and (c) the evolution of the internal state variable defining the state of damage. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-Integral approach was adapted to extract Cohesive stresses near the crack tip. A principal-stretch dependent internal damage state variable defines the damage in the Cohesive Layer. Within the Cohesive Layer, pristine and Cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic Cohesive Layer model to simulate interlaminar delamination. From a numerical stability standpoint, the viscous regularization effect of the viscoelastic constitutive equations in the Cohesive Layer helps mitigate numerical instabilities caused by elastic energy released due to crack growth, thereby enabling the FEA model to simulate the load-deflection response of the composite structure well beyond peak load. The present Cohesive-Layer based FEA model was able to accurately predict not only the macro level load-displacement curve, but also the micro level crack growth history in IM-7/BMI laminate before and after thermal aging, using only three parameters.Copyright © 2014 by ASME

  • The changes in flexural properties and microstructures of carbon fiber bismaleimide composite after exposure to a high temperature
    Composite Structures, 2014
    Co-Authors: Mohammad H. Haque, Samit Roy, Priyank Upadhyaya, Taylor H. Ware, Walter Voit
    Abstract:

    Recent increase in the use of carbon fiber reinforced polymer composites, especially for high temperature applications, has created new challenges to predict their service life. This paper examines the changes in weight loss and flexural properties along with the changes in microstructures of unidirectional carbon fiber reinforced bismaleimide with [016] and [9016] specimens, after exposure to 260 C for 3000 h in air. The percentage of fiber end area exposed to air in a specimen end section significantly influences the extent of these changes. The [9016] specimens have an order of magnitude higher fiber open ends than the [016] specimens, and their weight loss rate and loss in flexural modulus and strength are significantly higher than that of the [016] specimens. In three point bending, interlaminar shear leads to delamination preceding the final failure in compressive mode. A viscoelastic Cohesive Layer model has been implemented to simulate interlaminar delamination. Viscoelastic regularization of the constitutive equations of the Cohesive Layer used in this model not only mitigates numerical instability, but also predicts load–deflection behavior beyond peak failure load. The model is in a good agreement with experimental results and has been able to simulate the delamination failure successfully.

  • A novel numerical-experimental approach for predicting delamination in high temperature polymer matrix composites
    Composite Structures, 2013
    Co-Authors: Priyank Upadhyaya, Samit Roy, Mohammad H. Haque
    Abstract:

    Abstract In this paper, a novel numerical–experimental methodology is outlined to determine Cohesive stress and damage evolution parameters for pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic Cohesive Layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-integral approach was adapted to extract Cohesive stresses near the crack tip. A principal-stretch dependent internal damage state variable defines the damage in the Cohesive Layer. Within the Cohesive Layer, pristine and Cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic Cohesive Layer model to simulate interlaminar delamination. The present Cohesive-Layer based FEA model was able to accurately predict not only the macro-level load–displacement curve, but also the micro-level crack growth history in IM-7/BMI laminate before and after thermal aging.

  • Environmental Degradation of Interlaminar Shear Strength in Carbon/Epoxy Composites
    Fiber Reinforced Polymer (FRP) Composites for Infrastructure Applications, 2011
    Co-Authors: Avinash Reddy Akepati, Samit Roy, Abilash Nair, A. K. M. Ahasanul Haque, Piyush K. Dutta, Ashok Kumar
    Abstract:

    The effect of environmental and loading conditions on the degradation of Interlaminar Shear Strength (ILSS) of the carbon-epoxy composite specimens was studied. The hygrothermal conditions capture the synergistic effects of field exposure and extreme temperatures. A short beam shear test (SBST) was performed to determine the Interlaminar Shear Strength (ILSS) of environmentally aged composite specimens in accordance with ASTM D2344-84. Initially, a standard two-dimensional Cohesive Layer constitutive model was employed in order to simulate the experiment using an in-house FEA code (NOVA-3D). Numerical instabilities, encountered using the standard Cohesive Layer model, were overcome by incorporating viscoelastic regularization in the constitutive equations of the Cohesive Layer. This modification also enabled the analysis to continue beyond the point of peak failure load. The model was able to accurately simulate the load vs. displacement behavior of most of the SBST samples aged under various hygrothermal and synergistically applied stress conditions. Further, the effect of displacement rate on the ILSS of specimens was studied using NOVA-3D. The model indicated a strong dependence of viscoelastic Cohesive strength on the displacement rate. Regrettably, the predicted rate dependence could not be verified experimentally.

  • A mechanism-based multi-scale model for predicting thermo-oxidative degradation in high temperature polymer matrix composites
    Composites Science and Technology, 2011
    Co-Authors: Priyank Upadhyaya, Sushil Singh, Samit Roy
    Abstract:

    Abstract This paper describes a mechanism-based multi-scale model for life prediction of high temperature polymer matrix composites (HTPMC) under thermo-oxidative aging conditions. The multi-scale model incorporates molecular level damage such as inter-crosslink chain scission in a thermoset polymer due to thermo-oxidative aging of the polymer resin. The degradation of inter-laminar stress depends on remaining inter-crosslink density of thermo-set polymer in fiber/matrix interface region subjected to thermo-oxidative aging environment. The degradation of inter-laminar shear stress of thermo-oxidatively aged unidirectional IM-7/PETI-5 composite specimens at 300 °C was modeled using an in-house test-bed FEA code (NOVA-3D). A micromechanics based viscoelastic Cohesive Layer model was used to model delamination. The model is fully rate dependent and does not require a pre-assigned traction-separation law. Viscoelastic regularization of the constitutive equations of the Cohesive Layer used in this model not only mitigates numerical instability, but also enables the analysis to follow load–deflection behavior beyond peak failure load. The model was able to successfully simulate delamination failure in thermo-oxidatively aged unidirectional IM-7/PETI-5 composite, and the model predictions were verified using test data.

Florian Cavodeau - One of the best experts on this subject based on the ideXlab platform.

  • ethylene vinyl acetate copolymer aluminium trihydroxide composites a new method to predict the barrier effect during cone calorimeter tests
    Polymer Degradation and Stability, 2015
    Co-Authors: Florian Cavodeau, Josemarie Lopezcuesta, Belkacem Otazaghine, Rodolphe Sonnier, Christelle Delaite
    Abstract:

    Abstract This study presents the use of oedometric compression test in order to evaluate the breakdown of a protective Layer acting as a diffusion barrier (“barrier effect”) occurring during cone calorimeter tests for ethylene-vinyl acetate copolymer/aluminium trihydroxide (EVA/ATH) composites. The formation of an alumina Layer at the sample surface during burning insulates thermally the underlying material and reduces the heat release rate. The efficiency of this barrier depends on the cohesion of the Layer formed. This cohesion depends on the ability of the particles (ATH and synergistic mineral fillers) to self-arrange. During the test, the breakdown of this barrier can lead to an increase in HRR. The oedometric compression test allows assessing the ability of fillers to form a Cohesive Layer. Results obtained from compression modulus of filler powders are directly related to some aspects of the heat release rate curve of composites measured in cone calorimeter tests. Indeed, the appearance and the intensity of the second pHRR (related to the breakdown of the barrier Layer) in cone calorimeter test are related to the slope of oedometric compression curve.

  • Ethylene-vinyl acetate copolymer/aluminium trihydroxide composites: A new method to predict the barrier effect during cone calorimeter tests
    POLYMER DEGRADATION AND STABILITY, 2015
    Co-Authors: Florian Cavodeau, Belkacem Otazaghine, Rodolphe Sonnier, Jose-marie Lopez-cuesta, Christelle Delaite
    Abstract:

    This study presents the use of oedometric compression test in order to evaluate the breakdown of a protective Layer acting as a diffusion barrier (''barrier effect'') occurring during cone calorimeter tests for ethylene-vinyl acetate copolymer/aluminium trihydroxide (EVA/ATH) composites. The formation of an alumina Layer at the sample surface during burning insulates thermally the underlying material and reduces the heat release rate. The efficiency of this barrier depends on the cohesion of the Layer formed. This cohesion depends on the ability of the particles (ATH and synergistic mineral fillers) to self-arrange. During the test, the breakdown of this barrier can lead to an increase in HRR. The oedometric compression test allows assessing the ability of fillers to form a Cohesive Layer. Results obtained from compression modulus of filler powders are directly related to some aspects of the heat release rate curve of composites measured in cone calorimeter tests. Indeed, the appearance and the intensity of the second pHRR (related to the breakdown of the barrier Layer) in cone calorimeter test are related to the slope of oedometric compression curve.

Mohammad H. Haque - One of the best experts on this subject based on the ideXlab platform.

  • A Multi-Scale Viscoelastic Cohesive Layer Model for Predicting Delamination in HTPMC
    Volume 1: Advances in Aerospace Technology, 2014
    Co-Authors: Samit Roy, Priyank Upadhyaya, Mohammad H. Haque
    Abstract:

    In this paper, a novel numerical-experimental methodology is outlined to predict delamination in pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic Cohesive Layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. This unified model is fully rate-dependent and does not require a pre-assigned traction-separation law. The actual shape of traction separation law depends on: (a) the strain rate via the viscoelastic constitutive relationship, (b) the degree of thermo-oxidative aging via the changes in the experimentally measured creep compliance due to oxidation, and (c) the evolution of the internal state variable defining the state of damage. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-Integral approach was adapted to extract Cohesive stresses near the crack tip. A principal-stretch dependent internal damage state variable defines the damage in the Cohesive Layer. Within the Cohesive Layer, pristine and Cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic Cohesive Layer model to simulate interlaminar delamination. From a numerical stability standpoint, the viscous regularization effect of the viscoelastic constitutive equations in the Cohesive Layer helps mitigate numerical instabilities caused by elastic energy released due to crack growth, thereby enabling the FEA model to simulate the load-deflection response of the composite structure well beyond peak load. The present Cohesive-Layer based FEA model was able to accurately predict not only the macro level load-displacement curve, but also the micro level crack growth history in IM-7/BMI laminate before and after thermal aging, using only three parameters.Copyright © 2014 by ASME

  • The changes in flexural properties and microstructures of carbon fiber bismaleimide composite after exposure to a high temperature
    Composite Structures, 2014
    Co-Authors: Mohammad H. Haque, Samit Roy, Priyank Upadhyaya, Taylor H. Ware, Walter Voit
    Abstract:

    Recent increase in the use of carbon fiber reinforced polymer composites, especially for high temperature applications, has created new challenges to predict their service life. This paper examines the changes in weight loss and flexural properties along with the changes in microstructures of unidirectional carbon fiber reinforced bismaleimide with [016] and [9016] specimens, after exposure to 260 C for 3000 h in air. The percentage of fiber end area exposed to air in a specimen end section significantly influences the extent of these changes. The [9016] specimens have an order of magnitude higher fiber open ends than the [016] specimens, and their weight loss rate and loss in flexural modulus and strength are significantly higher than that of the [016] specimens. In three point bending, interlaminar shear leads to delamination preceding the final failure in compressive mode. A viscoelastic Cohesive Layer model has been implemented to simulate interlaminar delamination. Viscoelastic regularization of the constitutive equations of the Cohesive Layer used in this model not only mitigates numerical instability, but also predicts load–deflection behavior beyond peak failure load. The model is in a good agreement with experimental results and has been able to simulate the delamination failure successfully.

  • A novel numerical-experimental approach for predicting delamination in high temperature polymer matrix composites
    Composite Structures, 2013
    Co-Authors: Priyank Upadhyaya, Samit Roy, Mohammad H. Haque
    Abstract:

    Abstract In this paper, a novel numerical–experimental methodology is outlined to determine Cohesive stress and damage evolution parameters for pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic Cohesive Layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-integral approach was adapted to extract Cohesive stresses near the crack tip. A principal-stretch dependent internal damage state variable defines the damage in the Cohesive Layer. Within the Cohesive Layer, pristine and Cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic Cohesive Layer model to simulate interlaminar delamination. The present Cohesive-Layer based FEA model was able to accurately predict not only the macro-level load–displacement curve, but also the micro-level crack growth history in IM-7/BMI laminate before and after thermal aging.

Priyank Upadhyaya - One of the best experts on this subject based on the ideXlab platform.

  • A Multi-Scale Viscoelastic Cohesive Layer Model for Predicting Delamination in HTPMC
    Volume 1: Advances in Aerospace Technology, 2014
    Co-Authors: Samit Roy, Priyank Upadhyaya, Mohammad H. Haque
    Abstract:

    In this paper, a novel numerical-experimental methodology is outlined to predict delamination in pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic Cohesive Layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. This unified model is fully rate-dependent and does not require a pre-assigned traction-separation law. The actual shape of traction separation law depends on: (a) the strain rate via the viscoelastic constitutive relationship, (b) the degree of thermo-oxidative aging via the changes in the experimentally measured creep compliance due to oxidation, and (c) the evolution of the internal state variable defining the state of damage. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-Integral approach was adapted to extract Cohesive stresses near the crack tip. A principal-stretch dependent internal damage state variable defines the damage in the Cohesive Layer. Within the Cohesive Layer, pristine and Cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic Cohesive Layer model to simulate interlaminar delamination. From a numerical stability standpoint, the viscous regularization effect of the viscoelastic constitutive equations in the Cohesive Layer helps mitigate numerical instabilities caused by elastic energy released due to crack growth, thereby enabling the FEA model to simulate the load-deflection response of the composite structure well beyond peak load. The present Cohesive-Layer based FEA model was able to accurately predict not only the macro level load-displacement curve, but also the micro level crack growth history in IM-7/BMI laminate before and after thermal aging, using only three parameters.Copyright © 2014 by ASME

  • The changes in flexural properties and microstructures of carbon fiber bismaleimide composite after exposure to a high temperature
    Composite Structures, 2014
    Co-Authors: Mohammad H. Haque, Samit Roy, Priyank Upadhyaya, Taylor H. Ware, Walter Voit
    Abstract:

    Recent increase in the use of carbon fiber reinforced polymer composites, especially for high temperature applications, has created new challenges to predict their service life. This paper examines the changes in weight loss and flexural properties along with the changes in microstructures of unidirectional carbon fiber reinforced bismaleimide with [016] and [9016] specimens, after exposure to 260 C for 3000 h in air. The percentage of fiber end area exposed to air in a specimen end section significantly influences the extent of these changes. The [9016] specimens have an order of magnitude higher fiber open ends than the [016] specimens, and their weight loss rate and loss in flexural modulus and strength are significantly higher than that of the [016] specimens. In three point bending, interlaminar shear leads to delamination preceding the final failure in compressive mode. A viscoelastic Cohesive Layer model has been implemented to simulate interlaminar delamination. Viscoelastic regularization of the constitutive equations of the Cohesive Layer used in this model not only mitigates numerical instability, but also predicts load–deflection behavior beyond peak failure load. The model is in a good agreement with experimental results and has been able to simulate the delamination failure successfully.

  • A novel numerical-experimental approach for predicting delamination in high temperature polymer matrix composites
    Composite Structures, 2013
    Co-Authors: Priyank Upadhyaya, Samit Roy, Mohammad H. Haque
    Abstract:

    Abstract In this paper, a novel numerical–experimental methodology is outlined to determine Cohesive stress and damage evolution parameters for pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic Cohesive Layer model was implemented in an in-house test-bed finite element analysis (FEA) code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. To determine the model parameters, double cantilever beam (DCB) experiments were conducted on both pristine and isothermally aged IM-7/bismaleimide (BMI) composite specimens. The J-integral approach was adapted to extract Cohesive stresses near the crack tip. A principal-stretch dependent internal damage state variable defines the damage in the Cohesive Layer. Within the Cohesive Layer, pristine and Cohesive stresses were compared to estimate the damage parameters. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic Cohesive Layer model to simulate interlaminar delamination. The present Cohesive-Layer based FEA model was able to accurately predict not only the macro-level load–displacement curve, but also the micro-level crack growth history in IM-7/BMI laminate before and after thermal aging.

  • A mechanism-based multi-scale model for predicting thermo-oxidative degradation in high temperature polymer matrix composites
    Composites Science and Technology, 2011
    Co-Authors: Priyank Upadhyaya, Sushil Singh, Samit Roy
    Abstract:

    Abstract This paper describes a mechanism-based multi-scale model for life prediction of high temperature polymer matrix composites (HTPMC) under thermo-oxidative aging conditions. The multi-scale model incorporates molecular level damage such as inter-crosslink chain scission in a thermoset polymer due to thermo-oxidative aging of the polymer resin. The degradation of inter-laminar stress depends on remaining inter-crosslink density of thermo-set polymer in fiber/matrix interface region subjected to thermo-oxidative aging environment. The degradation of inter-laminar shear stress of thermo-oxidatively aged unidirectional IM-7/PETI-5 composite specimens at 300 °C was modeled using an in-house test-bed FEA code (NOVA-3D). A micromechanics based viscoelastic Cohesive Layer model was used to model delamination. The model is fully rate dependent and does not require a pre-assigned traction-separation law. Viscoelastic regularization of the constitutive equations of the Cohesive Layer used in this model not only mitigates numerical instability, but also enables the analysis to follow load–deflection behavior beyond peak failure load. The model was able to successfully simulate delamination failure in thermo-oxidatively aged unidirectional IM-7/PETI-5 composite, and the model predictions were verified using test data.