The SWR software finds a buckling load assuming that each of the load components Nx, Ny, and Nxy remain proportional. The method finds a scalar value that when multiplied by all three components, yields a bifuraction in the energy solution. The code returns the product of this scalar and the the load vector.
A negative load intensity for Nx and Ny denotes compression. For anisotropic laminates, the sign of Nxy may affect the result.