Stiffness predictions for closed-cell PVC foams

Abstract

Light-weight polymeric foams are frequently used in composite sandwich construction in which foam core material properties could significantly influence the overall performance of the sandwich structure. Foam mechanical properties usually depend on a number of factors, including foam density, cell microstructure, and properties of foam–matrix polymer. Although the properties of foam–matrix polymer are determined mainly by the properties of the foam base (parent) polymer, they are also affected by other factors such as foam processing conditions. With the large number of material and microstructure parameters that influence foam properties, modeling mechanical behavior of polymeric foams could be quite involved, especially if foam behavior is anisotropic. This paper describes an effort to predict static elastic stiffness of closed-cell PVC foams. PVC foams are modeled as transversely isotropic materials with properties in the foam rise direction different from those in the planar (plane of isotropy) directions. An engineering approach, based on fibrous composites, is developed to predict in-plane and out-of-plane stiffness of PVC foams. The validity of the engineering model for the PVC foam stiffness is first demonstrated through comparison with test results on DIAB H80 foam obtained from a systematic in-house test program. Comparison of the predictions with the stiffness properties reported by a PVC foam manufacturer for various other density foams is also carried out. Good agreements are obtained for the cases studied. Comparison of stiffness predictions obtained in the paper with predictions from other published models of isotropic foam behavior is presented.

Failure strength predictions for closed-cell polyvinyl chloride foams

“…This paper describes an analytical effort to predict mechanical strength of closed-cell PVC foams under static loading. The study presented here advances an earlier work 6 on modeling elastic stiffness of closedcell PVC foams. Closed-cell PVC foams are modeled as effective transversely isotropic materials with strength in the foam rise direction different from that in the planar (plane of isotropy) direction.…”

“…In this paper, they are determined using the expressions obtained from an earlier study 6 Figure 4) that are not parallel to the 2-3 plane to the total volume of foam-matrix polymer in the unit cell Note that a unit cell representation ( Figure 4) is used to facilitate modeling closed-cell PVC foam stiffness. 6 The cell is (closed-end) thin-wall rectangular parallelepiped with wall thickness t and a square cross-section in the 1-2 plane (plane of isotropy). The aspect ratio of the rectangular parallelepiped is taken to be the foam cell rise ratio ().…”

Test method development and determination of three-dimensional stiffness properties of polyvinyl chloride structural foams

“…The validity and effectiveness of the specimen configuration introduced in the study is clearly demonstrated for proper determination of the consistent transverse tensile stiffness of the foam. 11 12 and E 11 13 are in-plane compressive stiffness along the 1-direction obtained from specimens cut from 1-2 and 1-3 planes, respectively; E 11 is the average value of E 11 12 and E 11 13 . PVC: polyvinyl chloride.…”

Characterization and Model Validation for Large Format Chopped Fiber, Foamed, Composite Structures Made from Recycled Olefin Based Polymers

“…They concluded that the differential scheme and empirical equations using power-law and the square power-law provide reasonable estimates of the stiffness over a cell volume fraction ranging from 0 to 55%, a range that encompasses the cell density considered in this research. Lo et al [25] studied the effective stiffness for a transversely isotropic closed cell PVC foam using a unit cell representation. This is done by substituting an apparent volume fraction for the actual resin volume fraction.…”