Laminate materials are Anisotropic (have varying material properties in different directions) Extreme care must be taken to define these directions correctly within the FEA code. The consequence of getting this wrong is ‘garbage’ results! The example below shows the creation and orientation of a simple Femap model and subsequent analysis in Nastran (based on the model above) Two materials were defined (based loosely on Steel and Aluminium). Both materials have a ‘Strong’ direction 100x that of the ‘weak’ direction. Composite material definition and Analysis 1 The material 1 direction was defined in the global X direction as can be seen from the element material vectors below. Previous examples used an Orthotropic material model which, effectively, defines a ‘lumped’ Composite. In other words, an equivalent structure. However, we are now going to use a layup approach and define the various layers within the overall composite. This will give us the advantage of being able to see the stresses in the individual layers and look at inter-laminar bonds (de-lamination). The first analysis uses a (0,0,0) layup comprising 0.5mm Mat1, 2mm Mat2, 0.5mm Mat1.