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

摘要

Mechanical properties of rigid PVC foam are affected by material physical andstructural parameters, such as foam density and cell microstructure. The effect of foamdensity on its mechanical properties has been investigated by many investigators;however, the effect of microstructure remains to be clarified. The authors previouslyexamined out-of-plane compressive modulus and strength affected by density, cell riseratio and their interaction in Divinycell H100 PVC foam. In this paper recentlydeveloped accurate foam test methods were used to investigate the important effects offoam density and cell rise-ratio on stiffness properties of PVC foams under differentloading modes and along principal material directions. From an as-received large PVCfoam panel with measurable density variation, foam compression, tension and shear testspecimens with different densities and along different directions were prepared. Forcompression tests, straight-side specimens were used. In tensile tests, dumbbell shapespecimens were fabricated by adhesively- bonded prismatic foam pieces. Shear testswere conducted with a scale-down ASTM standard test method. Foam density wasdetermined for each test sample. The average foam cell aspect ratio (i.e., rise ratio) wasdetermined with optical microscopy. Relationships of cell rise ratio to foam densitywere found to be different for the out-of-plane and the in-plane test specimens. Theexperimental results showed that the dependence of foam compressive, tensile and shearstiffnesses on density and cell rise ratio is different along in-plane and out-of-planedirections. The results reveal the important combined effect of foam density and cellrise ratio on stiffness properties in different loading modes and directions. Previouslydeveloped foam stiffness models based on composite micromechanics were used tocorrelate and predict the experimentally determined stiffness under different loadingmodes and directions.