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Effects of Foam Density and Rise Ratio on 3D Mechanical Properties of PVC Foam under Different Loading Modes and Directions



Mechanical properties of rigid PVC foam are affected by material physical and structural parameters, such as foam density and cell microstructure. The effect of foam density on its mechanical properties has been investigated by many investigators; however, the effect of microstructure remains to be clarified. The authors previously examined out-of-plane compressive modulus and strength affected by density, cell rise ratio and their interaction in Divinycell H100 PVC foam. In this paper recently developed accurate foam test methods were used to investigate the important effects of foam density and cell rise-ratio on stiffness properties of PVC foams under different loading modes and along principal material directions. From an as-received large PVC foam panel with measurable density variation, foam compression, tension and shear test specimens with different densities and along different directions were prepared. For compression tests, straight-side specimens were used. In tensile tests, dumbbell shape specimens were fabricated by adhesively- bonded prismatic foam pieces. Shear tests were conducted with a scale-down ASTM standard test method. Foam density was determined for each test sample. The average foam cell aspect ratio (i.e., rise ratio) was determined with optical microscopy. Relationships of cell rise ratio to foam density were found to be different for the out-of-plane and the in-plane test specimens. The experimental results showed that the dependence of foam compressive, tensile and shear stiffnesses on density and cell rise ratio is different along in-plane and out-of-plane directions. The results reveal the important combined effect of foam density and cell rise ratio on stiffness properties in different loading modes and directions. Previously developed foam stiffness models based on composite micromechanics were used to correlate and predict the experimentally determined stiffness under different loading modes and directions.


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