I'm Tring to simulate delamination in composite using abaqus and Perform the tensile and bending tests with and without the delamination to study the difference in stiffness. Every example gives approximately the same results where is the problem?

Is it in the way of simulating delamination? With UN_Tied area between the layers.

Is it in the way of simulating the composite? With 3D continuum elements and Orthotropic properties. Using the composite feature in Abaqus.

Is it in the way of calculating the stiffness? With stress_ Strain curve in each direction..