Ply draping on arbitrarily shaped surfaces leads to local shearing of the plies. This manufacturing-induced artifact can lead to significant deviation between the assumed and effective mechanical properties. This is because the shearing can be on the order of several degrees before ply wrinkling becomes an issue. Thus, the configuration of the composite can vary considerably from point to point, as can the mechanical properties.

In order to reflect the mechanical properties’ dependence upon draping shear, ACP (Pre) provides a draping simulation tool. Upon specifying shear-dependent material properties in Engineering Data and enabling draping in ACP (Pre) for individual plies or Oriented Selection Sets, downstream analysis systems take this effect into account.

The draping shear angle is defined as:

|draped_transverse_angle - draped_fiber_angle| - 90

Where "draped_fiber_angle" and "draped_transverse_angle" denote the angles of the draped fiber and transverse directions with respect to the reference direction, respectively. Thus, a shear angle of 0 degrees indicates that the ply at the corresponding location is unsheared.