**4.1 Maximum stress criterion**

According to the Maximum Stress Criterion, for orthotropic materials, while the stresses in the principal directions of the material are lower than strength of the material in this direction, there are no fails, which means:


where *Xt* is the longitudinal tensile strength, *Yt* is the transverse tensile strength, *Xc* is the longitudinal compressive strength, *Yc* is the transverse compressive strength and *C* is the shear strength of the lamina.
