عنوان مقاله [English]
Solid foams are novel materials with outstanding characteristics that have found numerous applications in the construction of light, stiff structures during the past two decades. At the micro-level, solid foams benefit from a
cellular structure, which is composed of either closed or open cells. Open-cell foams, which were investigated in this study, are described as a network of inter-connected struts (or ligaments) with beam-like action. The mechanical design of foams requires their mechanical properties to meet certain criteria.These criteria can be satisfied by careful selection of the base material and the microstructural geometry. However, the selected material has to be manufactured, and manufacturing is by no means a perfect process. As a result, there is always a threat that the properties of the final material differ from the ones expected. The current study addresses this issue by exploring the effect of geometrical imperfections on the uniaxial properties of regular
open-cell foams. Such an investigation requires an appropriate approach, capable of relating the microstructural characteristics to the effective behavior of the material. An existing homogenization model was used for this
The model assumes the open-cell foam to be constructed from a repetition of the same unit-cell. The unit-cell in its original state has a regular structure, i.e. it comprises four identical members forming equal angles with respect to each other; the point at which these members coincide is called the unit-cell vertex. Imperfection was introduced in the form of small perturbations in the position of the unit-cell vertex. Accordingly, homogenization was employed to obtain the uniaxial stress-strain response of various perturbed microstructures. The results were then quantified in terms of four uniaxial parameters. The next step was to compare these parameters with their
counterparts that had been obtained for the regular microstructure. The consequence of this was to identify how the uniaxial response of originally regular, open-cell foam could vary when its microstructure was subjected to geometrical imperfections. In particular, this investigation revealed that different uniaxial parameters altered linearly (or pseudo-linearly) as the perturbation of the microstructure increased.