Elastic in–plane properties of cellular materials: Discrete approach

AbstractAn experimental study was carried out on the indentation of cellular materials under quasi-static conditions. The study concentrated on a closed cell rigid polyurethane foam, but other cellular materials were tested. Load (F) - penetration depth (x) curves were obtained for various types of indenters which fall into two main types: sharp indenters (e.g. normal nails) and blunt indenters (e.g. flat ended nails). The F(x) curves are similar for the two types with an initial high slope region followed by a lower slope region in which F increases linearly with x. Nevertheless, the mechanisms of indentation are completely different, with a blunt indenter pushing the material under it and a sharp indenter pushing it radially as it penetrates. The effect of dimensions and shape of the indenters on the F(x) curves was investigated and scaling relations could be derived. Penetration-removal cycles clarify the differences between the two types of indenters, and give additional information on the mechanics of indentation. The experiments were complemented with scanning microscope observations of sections of the indented material. Two approaches are advanced for modelling indentation: a discrete approach in which the cellular structure is taken into account and a continuum approach.

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Flat embeddment of monolayer cells, tissue sections, and other cellular materials attached onto glass substrate

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100161394 ◽

1990 ◽

Vol 48 (3) ◽

pp. 766-767

Author(s):

Jeffrey P. Chang ◽

Jaang J. Wang

Keyword(s):

Present Report ◽

Cellular Materials ◽

Cover Glass ◽

Tissue Sections ◽

Embedding Technique ◽

Exfoliated Cells ◽

Black Paper ◽

Cell Concentrations ◽

Flat Embedding

Flat embeddment of certain specimens for electron microscopy is necessary for three classes of biological materials: namely monolayer cells, tissue sections of paraffin or plastics, as well as cell concentrations, exfoliated cells, and cell smears. The present report concerns a flat-embedding technique which can be applied to all these three classes of materials and which is a modified and improved version of Chang's original methodology.Preparation of coverglasses and microslides. Chemically cleaned coverglasses, 11 × 22 mm or other sizes, are laid in rows on black paper. Ink-mark one coner for identifying the spray-side of the glass for growing cells. Lightly spray with Teflon monomer (Heddy/Contact Inductries, Paterson, NO 07524, U.S.A.) from a pressurized can. Bake the sprayed glasses at 500°F for 45 min on Cover-Glass Ceramic Racks (A. Thomas Co. Philadelphia), for Teflon to polymerize.Monolayer Cells. After sterilization, the Teflon-treated coverglasses, with cells attached, are treated or fixed in situ in Columbia staining dishes (A. Thomas Co., Philadelphia) for subsequent processing.

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