Some aspects on the zero-span tensile test

In this paper, we present some analytical and numerical results concerning the zero-span testing method, frequently used for quality control of cellulose fiber for papermaking. Of particular interest is the relationship between an apparent modulus obtained from the zero-span testing method and the elastic properties of the fibers. The apparent elasticity modulus is estimated using two energy theorems in elasto-statics in which the role of span length is explored. Analytical results, derived under the assumption that slippage between specimen and clamps does not occur, clearly show that the apparent modulus strongly depends on the span length. This is verified by the numerical results obtained using the finite element method. In addition to the above analysis, the effect of slippage is investigated, also by utilizing the finite element method, and it is found that for a specific case, the contribution from slippage to the total displacement depends strongly on the length of the span. Tensile tests at nominal zero span were conducted in an effort to further validate the analysis with relevant experimental data and it was concluded that there is qualitative agreement between the experimental results and the result of the analysis.