III.2.2.2 Composite Results

A few comments about the composite Results are given below presented in Tables III.2.6 to III.2.8:

1.

Composite Results have non-linear dependence on the primary unknowns (displacements and rotations). Therefore, composite Results obtained by linear combination of elementary Results are false.

2.

With Samcef, it is also possible to output ply Results in the upper and lower layers of each ply (codes 1xxxx and 2xxxx). FeResPost reads results at mid layer of each ply only. The other Results are skipped. (Note that most composite calculation methods usually use the forces in plies recovered at mid-thickness.)

3.

Even though the maximum stress and strain failure indices are presented in Samcef and FeResPost as tensorial Results, the six components for each location are not the components of a tensor. Therefore, the user must be very careful when using those Results. In particular transformations of coordinate systems for those Results are meaningless.

4.

Composite critical ply failure indices give for each element the maximum failure index in one of the plies. Also, the evaluation is done at the Gauss points of each ply and each elements and the maximum is collected.

Four methods devoted to the enabling or disabling of composite layered Results are defined in the generic “DataBase” class. These methods are presented in section I.1.3.2.

The correspondence between the failure indices read from Samcef result files and Results produced by CLA classes is as in Table III.2.9. Sometimes a single Samcef Result corresponds to two different CLA failure criteria. Then, the type of element (2D or 3D) allows the identification of the appropriate CLA criterion.

Important notes about the coordinate system associated with each value in the Result objects:

• The “ElemCS” coordinate system is obtained from the element topology. This means that it can be reconstructed using the nodes defining the element. So the element coordinate system looks more like a Nastran element coordinate system. This remark is necessary because Samcef documentation often uses the words “element coordinate system” to qualify what is rather a material coordinate system.

• The “ElemIJK” coordinate system is the same as “ElemCS”.

• The “MatCS” coordinate system corresponds to what is often called “element coordinate system” in Samcef documentation. This modification of terminology has been made to bring the meaning closer to a meaning closer to the one of Nastran Results.