This class corresponds to “IClaMat” interface.
Methods returning a 2D matrix, return a an Array with 2 dimensions. These methods are “getCompliance”, “getStiffness”, “getInPlaneCompliance”, “getInPlaneStiffness”, “getOOPSCompliance”, “getOOPSStiffness”, “getInPlaneLambdaT”, “getInPlaneLambdaH”. (In ruby extension, these methods return an array of arrays.)