Failure strength predictions for closed-cell polyvinyl chloride foams

Abstract

This paper describes an effort to model mechanical strength of closed-cell polyvinyl chloride foams under static loading. The study presented here is a continuation of an earlier study to model elastic stiffness of closed-cell polyvinyl chloride foams as effective transversely isotropic materials. An engineering approach is used in the study and governing equations are developed for predicting the strength of polyvinyl chloride foams. To account for foam microstructure and cell-shape anisotropy on foam strength, a unit cell representation of the polyvinyl chloride foam microstructure is used to derive equations to assess tensile and shear strengths of polyvinyl chloride foams. The differential stretching of polyvinyl chloride foam cell walls (in the rise direction and in the in-plane directions) on the strength of the foam-matrix polymer is also taken into account in modeling the mechanical strength of polyvinyl chloride closed-cell foams. The behavior of closed-cell polyvinyl chloride foams under compression is different from that under tension. In the paper, the equations for predicting compressive strength of closed-cell polyvinyl chloride foams are based on an approximate theory developed in an earlier study of compressive strength of unidirectional composites. The validity of the foam strength predictive equations, derived in the paper, is first demonstrated through comparison of the predictions with the results on Divinycell H (DIAB) foams obtained from a systematic in-house test program. A comparison is also carried out between the strength predictions and the test results published by two polyvinyl chloride foam manufacturers for different density polyvinyl chloride foams. Good agreements are found for all the different density foams studied.

Tensile properties of transversely isotropic closed-cell PVC foam under quasi-static and dynamic loadings

“…[16][17][18][19] In the past 20 years, some published references related to the investigation of tensile mechanical properties for PVC foam could be found. 11,16,[20][21][22][23][24][25][26][27][28][29][30][31][32] Gibson and Ashby 4 deeply discussed the tensile fracture behavior of polymer foam materials in their classic works, and proposed a theoretical model to predict the tensile strength of foam with the relative density. Colloca 11 and Walter 25 conducted the quasi-static tensile experiment to characterize the properties (including elastic modulus and strength) of PVC foams with various densities, and found that the material parameters of PVC foams are highly dependent on density.…”