A study on the development of the composite material for photoelastic experiment. 3rd Report, Analysis of the fracture mechanics of orthotropic materials by photoelastic experiment.

In this paper, the authors develop the least square method for obtaining the values of KI, KII and σox by photoelastic experiment using the orthotropic composite material. Further, the measuring method of the stress fringe value for orthotropic material was proposed in the case of which the principal axes of orthotropic material is not coincident with the direction of crack progress. Moreover, it became clear that the values of KI and KII are under the influence of the angle a between fiber and loading direction, and the values of KI and KII are related to the length of crack and the inclined angle β in the any cases of orthotropic material as isotropic material.