The microstructure of rigid polyurethane foams

Dawson, Jon; Shortall, J. B.

doi:10.1007/bf00809056

Cited by 62 publications

(39 citation statements)

References 9 publications

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“…The overall density, average cell size and cell geometric anisotropy ratio of the three foams, labeled A (least dense), B and C (densest), are presented in Table 1. Their geometrical characteristics are consistent with the conclusion by Dawson and Shortall [24] that cellular anisotropy decreases with a higher density.…”

Section: Fabrication Of Rigid Polyurethane Foamsupporting

confidence: 89%

Microstructure and Tensile Mechanical Properties of Anisotropic Rigid Polyurethane Foam

Ridha

Shim

2008

Exp Mech

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An understanding of the mechanical properties of solid foams facilitates effective use of such materials, which are often deployed in load-bearing applications such as impact absorbers, cushioning and sandwich structures. This study is an experimental investigation that focuses on the deformation response of rigid polyurethane foam to tension. Microstructural features such as the size and geometry of constituent cells and the struts that define the cell edges, as well as their stiffness and tensile strength, are examined. The nature of cell deformation and fracture are identified through microscopy and the associated micromechanics analyzed. Results show that the cells are elongated and thus the foam exhibits anisotropic properties. Flexure of the struts that define the cell edges is the primary mechanism governing deformation and failure. Information on the mechanical, microstructural and deformation characteristics elicited through this investigation will facilitate formulation of idealized cell-based models to account for the mechanical response of rigid polymeric foams.

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Section: Fabrication Of Rigid Polyurethane Foamsupporting

confidence: 89%

Microstructure and Tensile Mechanical Properties of Anisotropic Rigid Polyurethane Foam

Ridha

Shim

2008

Exp Mech

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“…It is important to examine the foam structure in the density range studied, to know the most appropriate modelling of mechanical properties [21]. Foam observations by scanning electron microscopy show the formed cells (Fig.…”

Section: Morphological Characterisationmentioning

confidence: 99%

Mechanical properties of high density polyurethane foams: I. Effect of the density

Saint-Michel

Chazeau

Cavaillé

et al. 2006

Composites Science and Technology

193

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This article presents the mechanical behaviour of rigid polyurethane foams with relative density (q f /q s ) above 0,3. The parameter taken into account is the density, which controls the foam architecture. The mechanical properties of the foams, characterised by large deformation compression tests and dynamic mechanical analyses, were compared to two theoretical models: (i) the Gibson and Ashby approach, widely used for foam description and (ii) the 2 + 1 phase model from Christensen and Lo, generally used for the description of particulate composite materials. In the studied density range, it is shown that the second approach is more appropriate. Moreover, the stress-strain curve and in particular yield stress have been modelled using two different approaches by extension of this model to the nonlinear domain.

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“…The great majority of previous works (N. C Hilyard and A. Cunningham, [12] Dawson et Shorthall [13] ) which have been interested in the three dimensional morphology of highly porous open cell foams assumed that the cellular structure is made of polyhedral cells in which the entire solid phase is comprised in the cell struts. Generally, the cells are assimilated to pentagonal dodecahedrons but other shapes have been also considered (cubic cells or tetrakaidecahedral cells).…”

Section: Modeling Of the Cells Shapementioning

confidence: 99%

Conductive Heat Transfer in Metallic/Ceramic Open‐Cell Foams

Coquard¹,

Loretz²,

Baillis³

2008

Adv Eng Mater

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During the last decade, solid foams which are characterized by a relatively high porosity (> 80 %), have known a strong development. Indeed, they allow to envisage a substantial improvement of the performance of standard materials in numerous technological fields. Notably, metallic and ceramic foams exhibit thermal, mechanical and exchange properties, which make them very interesting in lots of applications requiring multifunctionality. To illustrate this, we can cite a non-exhaustive list of functions for which they are usually used: ultra light panels, energy absorbing structures, heat dissipation media, electrodes for electric battery, ultrasound deflector, carrying structure for catalyst, medical prosthesis, heat exchanger _. In most of these applications, the knowledge of the thermal transport properties is of primary importance for the dimensioning of the structures. At ambient temperature, the heat transfer in solid foams is dominated by thermal conduction. To quantify the magnitude of heat conduction, one generally uses the effective conductivity k c which implies that the two-phase material behaves like a homogeneous conductive medium. This assumption is rigorously valid when the size of the pores is much lower than the dimensions of the materials, which is the case in solid foams. The effective conductivity depends on the porosity of the foam, the morphology of the material and on the properties of the two-phases. It is particularly difficult to estimate in solid foams due to the complexity of the geometry encountered and to the large difference between the thermal conductivity of fluid and solid phases.Numerous authors proposed empirical, analytical or numerical model depending on the porous morphology and on the conductivity of the phases to estimate the apparent conductivity of this type of materials. A study was conducted by Schuetz and Glicksmann. [2,3] They were interested in the conductivity of polymeric foams whose porous microstructure is very close to that of metallic and ceramic foams. Indeed, these foams are formed of closed or open cells made of cell struts and/or windows. The porosity of these foams is beyond 95 %. They modeled the foam as a network of thermal resistances and made several simplifications of the morphology and of the solution method to compute overestimating and underestimating values of the exact conductivity. These overestimating and underestimating values, given in, [2] are calculated analytically and are related to the conductivity of air and polymer and to morphological parameters:ek fluid 0:8 × 1 À e 2 À f s 3 k solid < k c

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The microstructure of rigid polyurethane foams

Cited by 62 publications

References 9 publications

Microstructure and Tensile Mechanical Properties of Anisotropic Rigid Polyurethane Foam

Microstructure and Tensile Mechanical Properties of Anisotropic Rigid Polyurethane Foam

Mechanical properties of high density polyurethane foams: I. Effect of the density

Conductive Heat Transfer in Metallic/Ceramic Open‐Cell Foams

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