Estimation of Mechanical Characteristics for Unidirectional FRP based on Oblique Unit Model considering Random Arrangement of Filaments

摘要

This paper describes FE modeling method of micro structure of unidirectional composites to estimate the strength of fibrous composite considering the uncertainness of micro structure. In several researches on FE modeling for micro structure, two types of models are mainly used. One is the unit model which arrangement of filaments is symmetric and regular. Another is the model which arranges the decades of filaments randomly. We propose an oblique unit (OU) model which has the random arrangement of filaments with relation between two filaments. Furthermore, the aspect ratio of unit model, position of filaments and angle of rotation of unit model can be changed easily. The effects of loading direction and the distance between filaments on the strength under transverse tensile loading have been investigated with the proposed method. The effects of thermal residual stress are also taken into considered. As the numerical results, it is cleared that the stress distributions and strengths varied largely due to the random parameters of the model and the thermal residual stress even though the volume fraction of fiber is same. Furthermore, the failure envelope which means the strengths for micro structure of UD FRP of out-of-plane share load and tensile/compressive load can be estimated by using the proposed OU model. The proposed OU model is useful to design for the micro structure considering effects of arrangement of nano-fiber on the mechanical properties. And, this method enables to reduce the computational cost radically, as compared with the conventional FE model which arranges more than 50 filaments.