An investigation of initial yield surfaces for unidirectional reinforced composites.

Abstract

Initial yield surfaces of unidirectional fiber reinforced composites subjected to combined longitudinal, transverse normal, and longitudinal shear loads are calculated. The composite is composed of filaments arranged in a periodic square array embedded in a matrix material. The constituent materials are assumed to be homogeneous and isotropic, while the composite is assumed to be macroscopically homogeneous and transversely isotropic. The finite element method, using linear strain triangles, is employed to calculate the stresses throughout the composite. Von Mises yield criterion is used to calculate the elastic limit of the local microscopic combined stresses in the composite. A parametric evaluation is carried out by changing individual constituent properties and evaluating the effect of this variation of the composite properties. Yield surfaces for several functional composites are included, as well as a computer program, in FORTRAN IV language, for the calculation of a yield surface.