Estimation of out of plane shear moduli for honeycomb cores with modal FEA
Keywords:PUR foams, dynamic compression, density, anisotropy, temperature
Polyurethane (PUR) foam is ideally suited as packing materials or dampers for many safety applications because of its chemical and design versatility and excellent energy absorbing properties. For this purpose, this paper investigates the effect of density, material orientation (anisotropy) and temperature on the main mechanical properties of cellular materials such as rigid polyurethane (PUR) foams. The experimental tests were carried out on specimens in the form of cubes using four different densities (40, 80, 120 and 140 kg/m3 ). The specimens were subjected to uniaxial dynamic compression with loading speed of 1.67 m/s, using different temperature (20, 60, 100°C). Significant differences in the behavior of the foam were observed depending on the density and testing conditions. Over the range of examined densities, the yield and plateau stresses as well as the Young modulus of the foam exhibited polynomial power-law dependencies with respect to density and have found that one of the most significant effects of mechanical properties in compression of rigid polyurethane foams is the density. In the process of absorbing impact energy, cell walls deform plastically and get damaged. After compression tests the foam shows a plastic collapse of cells, which increases the stress delivered to an almost constant strain (known as densification). In the moment of densification, due to the filling of the gaps in the foam, this one acts almost like a solid material.
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