Stiff Foam Research Articles

Microplane model for stiff foams and finite element analysis of sandwich failure by core indentation

Composite sandwich plates and shells are gaining increasing popularity in engineering practice, due to their high stiffness-to-weight ratio, low thermal conductivity and energy absorption characteristics. Modeling of the structural response of a sandwich member requires knowledge of the mechanical behavior of the materials used for the facings and the core. The paper presents a new constitutive model for closed-cell cellular materials, developed with the microplane approach. The model is then employed in a finite element analysis of three point bending tests of sandwich beams failing by core indentation. Good agreement of the numerical results with the experimental observations is achieved. This proves the new model to be capable of satisfactorily reproducing the mechanical response of cellular materials.

Underbalanced drilling with air offers many pluses: L. Shale, Oil & Gas Journal, 93(26), 1995, pp 33–39

A pressure overbalance during conventional drilling can cause significant fluid filtrate invasion and lost circulation. Fluid invasion into the formation can lead to formation damage, high mud costs, a need for expensive completions, and well productivity impairment. Because underbalanced drilling creates a natural tendency for fluid and gas to flow from the formation to the borehole, successful underbalanced drilling depends upon the appropriate selection of circulating fluid. The use of a compressible fluid in the circulating system, referred to as air drilling, lowers the downhole pressure, allowing drilling into and beyond these sensitive formations. The paper discusses the equipment needed; well control; downhole air requirements; air drilling techniques using dry air, air-mist, stable foam, stiff foam, and aerated-fluid; downhole fires; directional air drilling; and well completions.

Characterization of whey protein isolate obtained from milk microfiltration permeate

Summary - Whey protein was concentrated from milk microfiltration permeate or Cheddar cheese whey using batch ultrafiltration and diafiltration. Permeate flux declined more rapidly for milk microfiltrate during concentration, but similar flux profiles were observed on both wheys during diafiltration. Protein contents in concentrates from milk microfiltrate and cheese wheys were respectively 95 and 74% on a dry matter basis, while their fat contents were respectively 0.2 and 15%. Protein solubility of the milk microfiltrate isolate was over 95% between pH 3 and 8, while protein solubility of cheese whey concentrate varied between 75 and 90% over the same pH range. J3-Lactoglobulin in cheese whey concentrate showed ex1ensive structural alteration as evidenced by the low proportion of SH groups in native position. J3-Lactoglobulin structural alteration was less severe in protein isolated from milk microfiltrate, but still significant. Milk microfiltrate protein isolate showed better gelling properties th an cheese whey protein concentrate. Cheese whey protein concentrate did not foam at ail, while stiff and stable foams were produced from milk microfiltrate protein isolate. Gelation and foaming were very sensitive to the ionic environment and were controlled by a balance between the pH and the calcium concentration. Reduction of calcium content in milk microfiltrate protein isolate, using saline solution during diafiltration, had only slight effects of protein functional properties.

Formulation and Evaluation of a Peanut Milk Based Whipped Topping Using Response Surface Methodology

Using a rotatable design for two factors, 13 formulations of whipped topping were prepared containing 40% peanut milk as a source of protein. Whipped toppings were subjected to sensory evaluation using descriptive analysis. Color, overrun, viscosity and syneresis were analysed. Peanut-based whipped toppings were generally white and glossy with slightly stiff foam and fine, uniform air cells. There were significant differences in foam stiffness, uniformity of size of air cells and sweetness of various topping formulations. The physicochemical characteristics of formulated peanut-based whipped toppings were similar to those of commercially available whipped toppings.

Reduction of sitting pressures with custom contoured cushions

Previous research indicated that matching a cushion to the shape of the buttocks results in less tissue distortion and lower interface pressures. A system was developed to measure body contours and fabricate a cushion to match the measured contour. This project fabricated contoured foam cushions for 11 persons with spinal cord lesions (C5-L3). Mean pressures were compared on two flat and two contoured foams with different degrees of stiffness. Deflection characteristics on flat foam were compared to deflection on contoured foam in order to analyze loading differences. Material studies were determined by examining the load-deflection curves for flat foams of 1-, 2-, and 3-inch thicknesses. It was found that sitting on contoured foam resulted in a lower pressure distribution than sitting on flat foam (p less than 0.05), and sitting on a soft foam (ILD = 45) resulted in a lower pressure distribution than sitting on a stiffer foam (ILD = 55) (p less than 0.05). Results of the deflection measurements and compression tests were used to explain the loading differences at the seat interface of flat and contoured cushions. Loaded contoured foam demonstrated increased enveloping of the buttocks, decreased foam compression, and a more uniform pressure distribution. These attributes are typical of a safer sitting surface and may indicate less tissue distortion.

Tensile behavior of high‐density thermosetting polyester foams

AbstractThis paper shows that the tensile properties of high‐density stiff foams having cellular structures consisting of spherical voids can be described and predicted by simple rules. These rules are derived from other known and experimentally established relationships describing particulate systems of continuous glassy matrices containing a uniform dispersion of solid glass beads.

Extraction of nitrogenous material from winged bean [Psophocarpus tetragonolobus (L.) DC] flour and the preparation and properties of protein isolates

AbstractThe extractability of nitrogenous material from the seeds of 12 winged bean accessions has been investigated. Little variation in nitrogen content and extractability in water or salt solution was obtained, although decortication considerably reduced the levels of extraction. The effect of three oil extraction procedures on the extractability of nitrogenous material at different pH values is reported. Protein isolates were prepared and simple laboratory tests were used to evaluate their functional properties. The prepared winged bean isolates possessed very low bulk densities and high fat absorption values and the relationship between these factors was investigated further. Winged bean isolates showed high (100%) nitrogen dispersibilities and were able to form heat‐stable emulsions. They did not form gels under the conditions used except in the presence of CaCl2. Isolates prepared from unheated winged bean flour formed stiff but unstable foams. The relationship between the oil extraction procedure and isolate yield, purity and functional properties is discussed.

The Production and Use of Concentrated Skim Milk Foam

Summary 1. Reconstituted dry skim milks and condensed skim milks of 25 per cent to 30 per cent solids content were mechanically whipped in a few minutes to a stiff white foam. An overrun of 150 to 450 per cent and a foam stability of 10 to 90 minutes were found for different milks. 2. Wide variations were observed in the whipping properties of skim milks. High heat treatment usually improved whipping properties. Commercial milks prepared for baking purposes generally exhibited excellent whipping ability. 3. Skim-milk-whips were set by rennet or acid, but subsequent disturbance caused wheying off. Fruit-whips similar to an egg white product were prepared by adding sugar to the skim milk foam and stabilizing the whip by stirring fruit pulp into it.