Semi-crystalline polymers such as polyethylene, polypropylene and nylon are two-phase composite materials which develop strong textures under large deformations. The composite microstructure of these materials consist of coexisting crystalline lamellae and amorphous domains associated with each other in a fine plate-like structure. An aggregate of two-phase composite inclusions is used to model these materials. Special consideration is given to the low symmetry and the limited number of available slip systems in the crystalline phase. A micromechanical composite model based on the Sachs-inclusion type interaction law was developed and successfully applied to polyethylene. This model is now extended to low symmetry semi-crystalline polymers namely polypropylene (PP), nylon-6 and Poly(ethylene-terephthalate) (PET). We will show results from this model for PP and nylon-6 under different loading conditions. Both crystallographic and morphological textures are reported and discussed in comparison to the experimental results.