Load‐compression behavior of brittle foams

Abstract

SynopsisQuantitative relationships between the load-compression behavior and the physical characteristics of the foam matrix, previously reported for flexible systems, have now been extended to brittle foams. The shape of the compression curve is expressed in terms of fi(~), a dimensionless function of the compressive strain, while the stiffness, or load-bearing capacity, is defined by El, the apparent Young's modulus. Because the brittle matrix breaks-rather than flexes-when compressed, a brittle foam exhibits a flatter and wider plateau in the load-compression curve than a rigid (but ductile) foam of equivalent density, cell geometry, and Ej. These differences are expressed quantitatively by + ( t ) . It is important to distinguish between brittle foams and rigid, but ductile, foams. Since both types may exhibit the same stiffness, this distinction, particularly significant in energy absorbing applications, often is not considered in designing foam structures. Using the relationships established in this report, it is now possible to delineate precisely the characteristics a brittle foam must possess to meet a given load-compression specification.

Microcellular foaming of polymethylmethacrylate in a batch supercritical CO2 process: Effect of microstructure on compression behavior

“…An example of a phenomenological model was stated by Rusch. [39][40][41] However, a drawback of the model is its inaccuracy in describing the densification phase when, a consequence of the compression, internal voids progressively disappears. On the other hand, micromechanical models take into account the deformation mechanisms of the cell structure under loading, using several adimensional parameters that reflect these effects.…”

Sensing strain and damage in polyurethane/MWCNT nano-composite foams using electrical measurements

“…It can be noted that the stress-strain curves of the nano-composite foams deviate slightly from the 'nominal' description in that the linear and plateau regions are not clearly distinct. Instead, in this region the materials show an increasing linear behaviour, which is a common observation among polymer foams [36] and indicates plastic yielding earlier than usual. Nevertheless, the difference in the slope of the two phases is noticeable.…”

“…Each reflects different micro-structural compliance and failure mechanisms. [36,[38][39][40] As already mentioned, the first stage is the linearelastic response of the foam. During this stage, a number of deformation mechanisms occurs with the more dominant ones being the cell wall bending in combination with the compression of the gas contained within the closed foam cells.…”

“…MWCNT produced by catalyzed CVD were supplied by Arkema (France). According to the manufacturer, their diameters were 10-15 nm and they were more than 500 nm long, resulting in an aspect ratio (AR) in the range of [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. Previous studies [19,31,32] utilizing the same batch of CNTs showed good mechanical and electrical results for polymer composites.…”

Energy absorption diagrams of paper honeycomb sandwich structures

“…The evaluation of the cushioning properties of paper honeycomb sandwich structures is very important for optimizing package design. The methods for characterizing material cushioning properties include compression stressstrain curves, maximum acceleration and staticstress curves, 1,2 Janssen factor J, 3,4 Rusch curves, 5 energy absorption effi ciency curves 6 and energy absorption diagrams. Energy absorption diagrams identify the optimum energy absorption point of materials with different densities and at different strain rates, and can be achieved by experiment or model analysis.…”