Brittleness and toughness of polymers and other materials

Materials are often characterized in terms of their toughness, though more than one definition of toughness exists. Likely the most widely recognized means of defining material toughness, denoted here as τ, is by the area under the stress strain curve from a tensile test. Another important feature describing the nature of materials is that property known as brittleness, which has for a long time been much less quantitatively understood. Using a quantitative definition of brittleness provided in 2006, we demonstrate the existence of a quantitative relationship between τ and brittleness B, valid for polymers with a very wide range of chemical structures and properties, for some polymer-based composites, and also for steel and aluminum. We provide an equation relating toughness to brittleness, while for polymers we mark the determining influence of chemical structures on the properties B and τ.