Virtual enclosure model for thermal radiation extinction inside porous materials with closed cell structure

2015 ◽  
Vol 87 ◽  
pp. 79-91 ◽  
Author(s):  
Ari Seppälä ◽  
Olli Vartia ◽  
Pyry Seppälä ◽  
Kari Saari ◽  
Tuula Noponen ◽  
...  
Keyword(s):  
Thermal Radiation ◽  
Porous Materials ◽  
Cell Structure ◽  
Closed Cell ◽  
Radiation Extinction

scholarly journals Microstructural and Chemical Analysis of Polyurethane and Polyisocyanurate Foam Insulations

2021 ◽  
Author(s):  
Umberto Berardi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Performance ◽  
Cell Structure ◽  
Polymer Degradation ◽  
Chemical Characterization ◽  
Aging Behavior ◽  
Blowing Agent ◽  
Closed Cell ◽  
Physical Attributes ◽  
Cell Foam

For some closed cell foam insulation products, the thermal conductivity increases at low temperatures, contrary to single thermal resistance values provided by manufacturers. This phenomenon has been demonstrated in various polyurethane and polyisocyanurate insulations. The reduction in thermal performance has been attributed to the diffusion of air and blowing agent through the foam and to the condensation of blowing agent. Aging processes such as freeze-thaw cycling, moisture accumulation, and polymer degradation further increase thermal conductivity. The initial cell structure plays a role in dictating the thermal performance. To further understand the loss of thermal performance in closed cell foams, microstructure and chemical characterization was performed in this study. The aging behavior of foam insulations was analyzed by imaging foams with SEM and by measuring foam. Changes in the polymer physical attributes were identified and compared to increases in thermal conductivity. This project also used gas chromatography and quantified changes in pentane concentration in polyisocyanurate foams that have undergone aging

An ultra-simple universal model for the effective elastic properties of isotropic 3D closed-cell porous materials

2020 ◽  
Vol 249 ◽  
pp. 112531
Author(s):  
Pingping Yang ◽  
Ning Hu ◽  
Xiaojun Guo ◽  
Leiting Dong ◽  
Yang Chen ◽  
...  
Keyword(s):  
Porous Materials ◽  
Elastic Properties ◽  
Universal Model ◽  
Effective Elastic Properties ◽  
Closed Cell

Improved thermal radiation extinction in metal coated polypropylen microfibers

1993 ◽  
Vol 36 (11) ◽  
pp. 2789-2794 ◽  
Author(s):  
R. Caps ◽  
M.C. Arduini-Schuster ◽  
H.-P. Ebert ◽  
J. Fricke
Keyword(s):  
Thermal Radiation ◽  
Radiation Extinction

Porous mullite ceramics with a fully closed-cell structure fabricated by direct coagulation casting using fly ash hollow spheres/kaolin suspension

2020 ◽  
Vol 46 (11) ◽  
pp. 17508-17513
Author(s):  
Shuang Chen ◽  
Wei-Hao Cai ◽  
Jia-Min Wu ◽  
Yi-Xin Ma ◽  
Chen-Hui Li ◽  
...  
Keyword(s):  
Fly Ash ◽  
Cell Structure ◽  
Hollow Spheres ◽  
Kaolin Suspension ◽  
Closed Cell ◽  
Porous Mullite ◽  
Mullite Ceramics

scholarly journals Preparation and Properties of 3-Pentadecyl-phenol In-Situ Modified Foamable Phenolic Resin

2018 ◽  
Author(s):  
Tiejun Ge ◽  
Kaihong Tang ◽  
Yang Yu ◽  
Xiapeng Tan
Keyword(s):  
Molecular Structure ◽  
Phenolic Resin ◽  
Bending Strength ◽  
Cell Structure ◽  
In Situ Modification ◽  
Phenolic Foam ◽  
Closed Cell ◽  
Ft Ir ◽  
Limited Oxygen

In this present study, 3-pentadecyl-phenol was selected as a modifier to prepare a foamable phenolic resin with excellent performance, which was successfully prepared by in-situ modification. Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (1H NMR, 13C-NMR) were used to test and characterize the molecular structure of the modified resin. The results showed that 3-pentadecyl-phenol successfully modified the molecular structure of phenolic resin with a reduction in resin gel time. The effect of changing the added amount of 3-pentadecyl-phenol on the mechanical properties, microstructure and flame retardancy of the modified foam was investigated. The results showed that when the amount of added 3-pentadecyl-phenol was 15% of the total amount of phenol, this resulted in the best toughness of the modified foam, which could be increased to 300% compared to the bending deflection of the unmodified phenolic foam. The cell structure showed that the modified phenolic foam formed a more regular and dense network structure and the closed cell ratio was high. Furthermore, the compressive strength, bending strength, and limited oxygen index were improved, while the water absorption rate was lowered. However, the foam density could be kept below 40 mg/cm3, which does not affect the load.

scholarly journals Modeling of deformation and fracture of porous media taking into account their morphological composition

2020 ◽  
pp. 175-187
Author(s):  
A. S Shalimov ◽  
M. A Tashkinov
Keyword(s):  
Porous Materials ◽  
Numerical Models ◽  
Aluminum Matrix ◽  
Cell Types ◽  
Plastic Behavior ◽  
Elastic Model ◽  
Open Cell ◽  
Representative Volume ◽  
Closed Cell ◽  
Representative Volume Elements

This paper investigates the mechanical behavior and fracture of porous materials with an aluminum matrix. The purpose of the work was to create numerical models of failure of representative volume elements of such materials and to reveal the dependences of the nature of the failure processes on their structural morphology. Representative volume elements of these materials are random non-uniform structures of closed-cell and open-cell types. To create three-dimensional geometric models of the closed-cell structures, methods of sequential synthesis the possibility of their mutual intersection were used. For creation of models of interpenetrating structures of the open-cell type, methods based on the analytical determination of surfaces separating the two phases are used. In this paper, three approaches to fracture mechanics of representative volume elements of porous materials were studied and implemented. The first approach is an implementation of the elastic model and damage accumulation based on elastic properties degradation in accordance with the criterion of maximum stresses with reduction of the stiffness matrix coefficients in individual elements. The second approach is an implementation of the same model, but with removal of the failed elements. The third approach is based on the Johnson-Cook elastic plastic behavior and fracture model. Numerical modeling of the representative volumes was carried out with finite element analysis using each of the above approaches. The influence of the internal structure of the representative volumes of the porous materials on the processes of deformation and failure was studied on the example of several structures of open-cell and closed-cell types. The influence of stress concentrators on the distribution of stresses in representative volumes and character of their subsequent failure has been studied.

Investigation of Sound Absorption Feature of Closed-Cell Aluminum Foams Combined with Porous Materials

2017 ◽  
Vol 9 (3) ◽  
pp. 392-397
Author(s):  
Lisi Liang ◽  
Shiwei Liu ◽  
Junxue Zhao ◽  
Manbo Liu ◽  
Qi Sun
Keyword(s):  
Porous Materials ◽  
Sound Absorption ◽  
Absorption Feature ◽  
Aluminum Foams ◽  
Closed Cell

scholarly journals Preparation and Properties of the 3-pentadecyl-phenol In Situ Modified Foamable Phenolic Resin

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1124 ◽  
Author(s):  
Tiejun Ge ◽  
Kaihong Tang ◽  
Yang Yu ◽  
Xiapeng Tan
Keyword(s):  
Molecular Structure ◽  
Phenolic Resin ◽  
Bending Strength ◽  
Cell Structure ◽  
In Situ Modification ◽  
Phenolic Foam ◽  
Closed Cell ◽  
Ft Ir ◽  
Limited Oxygen

In this present study, 3-pentadecyl-phenol was selected as a modifier to prepare a foamable phenolic resin with excellent performance, which was successfully prepared by in situ modification. Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (1H NMR, 13C NMR) were used to test and characterize the molecular structure of the modified resin. The results showed that 3-pentadecyl-phenol successfully modified the molecular structure of phenolic resin with a reduction in the resin gel time. The effect of changing the added amount of 3-pentadecyl-phenol on the mechanical properties, microstructure, and flame retardancy of the modified foam was investigated. The results showed that when the amount of added 3-pentadecyl-phenol was 15% of the total amount of phenol, this resulted in the best toughness of the modified foam, which could be increased to 300% compared to the bending deflection of the unmodified phenolic foam. The cell structure showed that the modified phenolic foam formed a more regular and dense network structure and the closed cell ratio was high. Furthermore, the compressive strength, bending strength, and limited oxygen index were improved, while the water absorption rate was lowered. However, the foam density could be kept below 40 mg/cm3, which does not affect the load.

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