The linear, finite-membrane-strain, fully integrated, quadrilateral shell element (S4) should be used when greater solution accuracy is desired. This element is well suited for problems prone to membrane- or bending-mode hourglassing or for problems where in-plane bending is expected.

The linear, finite-membrane-strain, reduced integration, quadrilateral shell element (S4R) is robust and is suitable for a wide range of applications.

The linear, finite-membrane-strain, triangular shell element (S3/S3R) can be used as a general-purpose element. A refined mesh may be needed to capture bending deformations or high strain gradients because of the constant strain approximation in the element.

To account for the influence of shear flexibility in laminated composite shell models, use the shell elements suitable for modeling thick shells (S4, S4R, S3/S3R, S8R); check that the assumption of plane sections remaining plane is satisfied.

Quadratic shell elements, either quadrilateral or triangular, are very effective for general, small-strain, thin-shell applications. These elements are not susceptible to shear or membrane locking.

If you must use second-order elements in contact simulations, do not use the quadratic, triangular shell element (STRI65). Use the 9-node, quadrilateral shell element (S9R5) instead.

For very large models that will experience only geometrically linear behavior, the linear, thin-shell element (S4R5) will generally be more cost-effective than the general-purpose shell elements.