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Effects of Density and Cell Rise Ratio on Compressive Stiffness and Strength of PVC Structural Foam



A study has been conducted to investigate the important effects of foam density and cell rise ratio on compressive mechanical properties of closed-cell PVC structural foam. Taking advantage of density variation in an as-received large PVC foam panel, foam compression specimens with different densities from the panel were prepared. Straight-side specimens with different gage-section length-to-width ratios were used for foam out-of-plane compressive stiffness study. For strength and failure mode evaluation, foam specimens with reduced gage sections were used. Test results show that foam compressive stiffness did not correlate linearly with either foam density or cell rise ratio. Similar behavior was observed for the foam compressive failure strength. Compressive failure modes were found to include foam cell buckling and formation of a localized shear band across the entire specimen cross-section. Recently developed foam compressive stiffness and strength models based on foam microstructure and micromechanics were used to correlate analytical predictions with experimentally determined foam compressive stiffness and strength. The results indicate that foam density and its cell rise ratio alone cannot properly address the effect of individual material and microstructure parameters on foam compressive properties. Their interactive roles and combined effect must be considered simultaneously in the modeling, analysis and experimental evaluation of foam mechanical properties. For the light-weight closed-cell PVC foam tested in the study, an approximately linear relationship with the product of foam density and cell rise ratio was found for both foam compressive stiffness and compressive strength.

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