II.4.4 Manipulation of plies

The “clearPlies” method has no argument and erases all the plies defining a ClaLam object. After the method has been called, the number of plies of the laminate is zero.

One way to define the plies of the laminate is to add successively all the plies defined in the laminate starting at the bottom layer. The “addPly” method allows to insert plies in a ClaLam. This method has four or five arguments.

• “PlyId” is the global identifier of the ply. This identifier can be an integer, a String or a pair "integer-String" stored in an Array. If one decides not to specify a global ID for the ply, the argument can be omitted (optional argument).
• “MatId” is the material id of the ply. This identifier must correspond to an existing material stored in a ClaDb object. The identifier is used internally by the ClaLam class to retrieve material properties and calculate laminate properties.
• “Thickness” is a Real argument corresponding to the thickness of the ply. The units must be consistent with those of other data. For example, the thickness may have to be given in meters.
• “Angle” is a Real argument corresponding to the orientation of the ply in the laminate. This angle is specified in degrees.
• “IlssInf” is the inter-laminar shear stress allowable between the ply being added and the previous ply (lower ply in the layup).

The sequence of plies in the laminate corresponds to the order of addition of the plies by calls to the “addPly” method. Of course each call of the method “addPly” increases the number of plies of the laminate by one.

Instead of defining the sequence of plies sequentially by successive calls to “addPly” method, the data of each ply can also be defined in random order by calls to “setPly” method. Its arguments are nearly the same as those of the “addPly” method:

• “Index” is the position in laminate of the ply for which data are defined. It is an integer such that $0\le i<N$ where $N$ is the number of plies defined in the Laminate.
• “PlyId” (see “addPly” method). This argument is optional.
• “MatId” (see “addPly” method).
• “Thickness” (see “addPly” method).
• “Angle” (see “addPly” method).
• “IlssInf” (see “addPly” method).

As the “PlyId” second argument is optional, the method has 5 or 6 arguments. The “setPly” method is very handy when one defines a new laminate by modifying a few plies from a previously existing one. Of course, an entirely new laminate can also have its ply data initialized with “setPly” method, but then the number of plies must first be set... “setNbrPlies” method has one argument and sets the number of plies. Note that the ply definition data previously stored in the laminate may have random values after using this method.

Two methods allow to access and examine the plies stored in a ClaLam object:

• “getNbrPlies” has no argument and returns the number of plies.
• “getPlyData” returns the data for one specific ply. The method has one argument: the local index of the ply in the laminate (its position in the lay-up). if the laminate has $N$ plies, then the index must be $0\le i\le N-1$. (The first ply has index 0.)

  The method returns an Array containing 5 elements corresponding to the arguments of the “addPly” method.

Obviously, the different data inserted in, or retrieved from the ClaLam object should be consistent with the set of units attributed to the same object. This set of units can be attributed to the object after initialization of the data.