The strength of Japanese paper is known to be strongly dependent upon the structure of its constituent fibers. The present study has been conducted to evaluate theoretically the fracture strength of Japanese paper. The paper was postulated to be made with the three dimensional net structure of fibers. The fracture strength of the paper was discussed on the basis of investigations related to the crack propagation mode of paper. The crack growth rate of paper was measured experimentally. Its rupture speed was calculated from the cut rate of strips coated on the paper with an electro-conductive paint.
The theoretical analyses showed that crack growth rate was dependent upon the cut direction of specimen sheet, the fiber geometry and its elastic modulus. This theoretical predictions were found to be consistent fairly with the experimental results.
