Load‐compression behavior of brittle foams

Quantitative 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 ψ(ε), a dimensionless function of the compressive strain, while the stiffness, or load‐bearing capacity, is defined by E f , 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 E f . These differences are expressed quantitatively by ψ(ε). 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.