6.9 Laminate notation

The laminate stacking sequence (LSS) describes the laminate by listing the laminas (also called layers) from bottom to top of the laminate. For each lamina, three values are given: the lamina name, the orientation, and the thickness. The orientation is the angle $\theta $ (in degrees) measured counterclockwise from the laminate coordinate system towards the fiber direction of the lamina, as show here:

Figure 6.3: Definition of lamina and laminate coordinate systems. Click the Back button on your browser to return to your previous page.

In print, the LSS notation consists of a list of angles between square brackets. For example $[0/90]$ means that the bottom ply is oriented along x and the top ply along y.

Balanced, adjacent angle ply groups can be written either as $[45/-45]$ or $[\pm 45]$.

The notation was originally developed for laminates made with prepreg, for which all laminas (or plies) have the same thickness. If multiple plies are adjacent, the number of repeated plies is indicated with a subscript, such as $[0/90/90/0]=[0/90_2/0]$. When the laminate is not made with prepreg, the thickness may not be multiple of ply thickness but they may have any value that the engineer chooses. This happens for all processing methods other than prepreg layup. In this case, the subscript is the thickness, such as in $[0/90_{5.0}/0]$. The units used for thickness must be given. Common units are mils and mm. Mils are are thousands of an inch. Most prepreg comes with thickness of 5.0 mils, which is 0.127 mm.