The SWR software treats a core as an additional layer in a laminate, with lamination theory applied to determine the effective stiffness properties. This approach assures that all of the plate mechanics are self-consistent. However, the approach requires that the user enter values for the inplane properties of the core. If these are not known, small, but nonzero values may be entered. The properties should satisfy the energy bounds for an orthotropic material. The local coordinates for the core material are the same as for a facesheet layer; the z-direction is through the thickness. No additional orientation angle is applied to the core, which means that the core x-direction is identical to the plate global x-direction.