Paperboard Mechanical Properties at Fracture

Paperboard mechanical properties at fracture during uniaxial tests is an interplay between available elastic energy at fracture and the fracture energy needed to separate the sample into two parts. A test at a critical length, the load vs. elongation curve immediately falls from a point of instability to zero load. Whereas, a test at a stable length give a stable descending load-elongation curve with no discontinuous drop of the load.

Tests, less than the stable length, give the cohesive law of the paper. The cohesive law is fully characterized by the tensile strength, the maximum slope of the curve and a parameter represents the shape of the law. From the parameters two length measure are defined giving a ratio 푔. It is shown that the ratio 2푔 is the ratio the between the critical length and the stable length.

The finding is applied to an infinite paper sheet with a crack length of 2푎 loaded with a remote loading. It is shown that length of the processes zone is proportional to the critical length of the paperboard and independent of an applied load, at small scale yielding (using the Dugdale model).