Achileas,

According to manual, here is what we have on the Interlaminar stress:

In the analysis of layered composite structures, shell elements are widely used to keep the computational effort reasonable. In-plane stresses and even transverse shear stresses can be predicted with accuracy using shells based on the first-order shear deformation theory (FSDT). However, in the analysis of thick-walled curved structures, interlaminar normal stresses (INS) can play a significant role. The normal stresses may affect the failure mode or even cause delamination failure. INS computation is not commonly available in shell element formulations, which leads to use of computationally expensive solid modeling instead.

The approach by Roos et al. for INS computation of doubly curved laminate structures represents an alternative for solid modeling. The basis for the INS calculation is the displacement solution obtained from a shell based model. In conjunction with the INS approach, transverse shear stresses are computed with the approach presented by Rohwer and Rolfes. When considered at layer interfaces, transverse shear stresses are referred to as interlaminar shear stresses (ISS).

R. Roos, G. Kress, and P. Ermanni. A post-processing method for interlaminar normal stresses in doubly curved laminates. Journal of Composite Structures. Vol. 81. pp. 463-470. 2007.

K. Rohwer. Improved Transverse Shear Stiffnesses for Layered Finite Elements. DFVLR-FB. 1988.

R. Rolfes and K. Rohwer. Improved Transverse Shear Stresses in Composite Finite Elements Based on First Order Shear Deformation Theory. Int. J. for Num. Meth. in Eng. Vol. 40. pp. 51-60. 1997.

In this part of the manual, there are 4 examples with step by step instructions. In the first 2, you can compare Composite Shell against a Composite Solid. Please check those out.

Also, please take a look at the Limitations and recommendations listed here for Interlaminar normal stress calculation.

For more details on the math involved behind the Interlaminar Normal Stress and the Transverse Shear Stress, please check out the underlying links.

There are also a few videos on the ANSYS TechTips Channel on ACP. Please check them out and see if it helps:

Hope this helps.

Regards,

Sandeep