Estimation of out of plane shear moduli for honeycomb cores with modal FEA

Authors

  • Emanoil Linul
  • Liviu Marsavina
  • Tomasz Sadowski

Keywords:

PUR foams, dynamic compression, density, anisotropy, temperature

Abstract

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.

References

GIBSON, L.J. ASHBY, M.F., Cellular solids, Structure and properties, Second edition, Press Syndicate of the University of Cambridge, 1997.

AJDARI, A., Mechanical behaviour of cellular structures a finite element study, Master on Science in Mechanical Engineering, Northeastern University, Boston, Massachusetts, 2008.

MARSAVINA, L., KOVACIK, J., LINUL, E., Experimental validation of micromechanical models for brittle aluminium alloy foam, Theor. Appl. Fract. Mech., 83, pp. 11–18, 2016.

LINUL, E., ?ERBAN, D.A., MARSAVINA, L., KOVACIK, J., Low-cycle fatigue behaviour of ductile closed-cell aluminium alloy foams, Fatigue Fract. Eng. Mater. Struct., 2016, http://dx.doi.org/10.1111/ffe.12535.

KOVÁCIK, J., JERZ, J., MINÁRIKOVÁ, N., MARSAVINA, L., LINUL, E., Scaling of compression strength in disordered solids: metallic foams, Frattura ed Integrita Strutturale, 36, pp. 55–62, 2016.

MARSAVINA, L., CONSTANTINESCU, D.M., LINUL, E., STUPARU, F.A., APOSTOL, D.A., Experimental and numerical crack paths in PUR foams, Eng. Fract. Mech., 167, pp. 68–83, 2016.

LINUL, E., ?ERBAN, D.A., MARSAVINA, L., SADOWSKI, T., Assessment of collapse diagrams of rigid polyurethane foams under dynamic loading conditions, Arch. Civ. Mech. Eng., 17, 3, pp. 457–466, 2017.

LINUL, E., ?ERBAN, D.A., VOICONI, T., MARSAVINA, L., SADOWSKI, T., Energyabsorption and efficiency diagrams of rigid PUR foams, Key Engineering Materials, 601, pp. 246–249, 2014.

?ERBAN, D.A., LINUL, E., VOICONI, T., MARSAVINA, MODLER, N., Numerical evaluation of two-dimensional micromechanical structures of anisotropic cellular materials: case study for polyurethane rigid foams, Iran. Polym. J., 24, pp. 515–529, 2015.

LINUL, E., MARSAVINA, L., KOVACIK, J., Collapse mechanisms of metal foam matrix composites under static and dynamic loading conditions, Mat. Sci. Eng. A-Struct., 690, pp. 214-224, 2017, http://dx.doi.org/10.1016/j.msea.2017.03.009.

LINUL, E., MARSAVINA, L., Assessment of sandwich beams with rigid polyurethane foam core using failure-mode maps, Proc. Rom. Acad. A, 16, 4, pp. 522–530, 2015.

?ERBAN, D.A., LINUL, E., SARANDAN, S., MARSAVINA, L., Development of parametric Kelvin structures with closed cells, Solid State Phenomena, 254, pp. 49–54, 2016.

MARSAVINA, L., LINUL, E., VOICONI, T., NEGRU, R., Experimental investigations and numerical simulations of notch effect in cellular plastic materials, IOP Conference Series: Materials Science and Engineering, 123, 1, 012060, 2016.

BIRSAN, M., SADOWSKI, T., MARSAVINA, L., LINUL, E., PIETRAS, D., Mechanical behavior of sandwich composite beams made of foams and functionally graded materials, Int. J. Solids Struct., 50, pp. 519–530, 2013.

MARSAVINA, L., CONSTANTINESCU, D.M., LINUL, E., VOICONI, T., APOSTOL, D.A., SADOWSKI, T., Evaluation of mixed mode fracture for PUR foams, Procedia Materials Science, 3, pp. 1342–1352, 2014.

VOICONI, T., NEGRU, R., LINUL, E., MARSAVINA, L., FILIPESCU, H., The notch effect on fracture of polyurethane materials, Frattura ed Integrita Strutturale, 30, pp. 101–108, 2014.

MARSAVINA, L., LINUL, E., VOICONI, T., CONSTANTINESCU, D.M., APOSTOL, D.A., On the crack path under mixed mode loading on PUR foams, Frattura ed Integrita Strutturale,

, pp. 444–453, 2015.

NEGRU, R., MARSAVINAA, L., VOICONI, T., LINUL, E., FILIPESCU, H., BELGIU, G., Application of TCD for brittle fracture of notched PUR materials, Theor. Appl. Fract. Mech. 80, pp. 87–95, 2015.

MARSAVINA L, CONSTANTINESCU, D.M., LINUL, E, VOICONI, T., APOSTOL, D.A., Shear and mode II fracture of PUR foams, Eng. Fail. Anal., 58, pp. 465–476, 2015.

LINUL, E., MARSAVINA, L., Prediction of fracture toughness for open cell polyurethane foam by finite-element micromechanical analysis, Iranian Pol. J., 20, 9, pp. 735–746, 2011.

LINUL, E., VOICONI, T., MARSAVINA, L., Determination of mixed mode fracture toughness of PUR foams, Structural Integrity and Life, 14, 2, pp. 87–92, 2014.

MARSAVINA, L., CONSTANTINESCU, D.M., LINUL, E., APOSTOL, D.A., VOICONI, T., SADOWSKI, T., Refinements on fracture toughness of PUR foams, Eng. Fract. Mech., 129, pp. 54–66, 2014.

MARSAVINA, L, LINUL, E., Fracture toughness of polyurethane foams. Experimental versus micromechanical models, Fracture of Materials and Structures from Micro to Macro Scale; 18th European Conference on Fracture, Dresden, Germany, August 30 – September 03, 2010.

AVALLE, M., Characterization of polymeric structural foams under compressive impact loading by means of energy-absorption, Int. J. Impact Eng., 25, pp. 455–472, 2001.

AVALLE, M., BELINGARDI, G., IBBA, G., Mechanical models of cellular solids: Parameters identification from experimental tests, Int. J. Impact Eng., 34, pp. 3–27, 2007.

Published

2016-06-15