Papers by Keyword: Closed-Cell Foam

Abstract: As the trend for lighter more efficient structures continues, the requirement for alternative materials follows. One material that has gained attention more recently is porous metallic foam. One drawback to these materials is that there is limited pedigree and understanding of their performance. As with all materials, the use of metallic foam for structures requires knowledge of its mechanical properties; including at high-strain rates. The focus of this paper is to determine the compressive mechanical properties and the influencing parameters for AISI 4340 steel closed-cell foam under high-strain rates (776s^-1 to 3007s^-1). ANSYS commercial finite element code is used to simulate a closed-cell sample under a split Hopkinson pressure bar test. In this paper the pores are considered to be spherical in shape for simplification while various parameters such as the pore size, the number of pores, the distribution of pores, and the strain rate are varied. Each of these parameters gives this material a unique response which is presented in this paper.

Abstract: Composite thermal insulation material can be made from expanded and vitrified small balls and other inorganic insulation lightweight aggregate. According to the hydration, hardening mechanism of inorganic gel material and materials thermal insulation mechanism, we can eliminate the heat convection of gas inside the holes by using foaming technology, and micro holes can reduce radiation heat transfer between the pore walls so as to further improve the thermal insulation properties of solid materials.

Abstract: The role of cell wall microstructure in influencing the mechanical behaviour of closed cell aluminium foam was investigated. The morphologies of the cell wall were characterized by using optical microscopy. An attempt has been made to describe the relationship between the microstructure of cell wall and mechanical properties primarily pertaining to the compressive response. The closed-cell foams in as-foamed and aged condition, having rather similar relative densities and cell structures but significantly different cell-wall microstructure have been examined. It was found that in as foam condition thick dendritic structure is present. On ageing at different temperatures for different duration, it was found that as ageing progresses the dendritic structure break in to finer precipitates resulting in improvement in microstructure of the cell wall. The compression tests also affirm the microstructural contribution to energy absorption capability.

Abstract: The objective of this work is to numerically investigate the elastoplastic behavior of closed-cell foams. Anisotropic geometry with ellipsoidal pores is considered and the contribution of the inner gas pressure within the cells is incorporated to the model. Based on face centered cubic (FCC) arrangements of pores and the finite element method, macroscopic elastic constants and initial yield stress against the relative density and cell aspect ratio are discussed in this paper. Through a systematic study we find that the initial yield stress is dependent on the loading direction. The inner gas pressure results in the asymmetry of uniaxial tensile-compressive stress-strain curves and significantly affects the initial yield stress of the foams for different loading directions.

Abstract: A thorough investigation of the failure mechanisms of composite sandwich beams under four- and three-point bending and cantilever beams was undertaken. The beams were made of unidirectional carbon/epoxy (AS4/3501-6) facings and a PVC closed-cell foam (Divinycell) core. Two types of core material H100 and H250 with densities 100 and 250 kg/m3, respectively, were used. The failure modes investigated are face sheet compressive failure, core failure and facing wrinkling. The various modes have been studied separately and both initiation and ultimate failure have been determined. Initiation of a particular failure mode and triggering and interaction with other failure modes was also investigated.