Byway of introduction, the present state of knowledge is reviewed on the deformations of paper under uniaxial tension in the three principal directions- elongation, lateral contraction and change in thickness. Their measurement is briefly described in order to show the relationship between the experimental situation and the definition of the terms by which the deformations are characterised.
Following this, the results of tensile tests with straining cycles are presented. These show, apart from the elongation, the pattern of the cross-sectional changes and their reversible and irreversible components. Using laboratory handsheets, the effects studied were of manufacturing variables such as the grammage, the degree of refining and calendering, also of the furnish and of loading.
These investigations were supplemented by measurements on machine-made papers. It was found that the relationship between plastic elongation and total elongation is almost the same for all papers. There is also a strong similarity between the patterns of lateral contraction of the various papers, for which Poisson ratios ᵛₓᵥ = 0.16 – 0.34 and ᵛₓᵥ = 0.04 – 0.10 were found. By contrast, the change in thickness varies considerably from paper to paper and shows negative as well as positive Poisson ratios.
The comparison with results obtained on other sheet-like materials such as packaging foils and various printing substrates demonstrates the peculiarities of the deformation behaviour of paper.
Concluding the article, an attempt is made t o arrive at a general formulation of the load/deformation behaviour of paper and it is here that the significance of the investigated fundamental properties of paper for its conversion and use become apparent.