Thickness
a) load on the top surface
z = h 2
σ 13 = σ 23 = 0 , σ 33 = σ 0 sin ( m π x 1 a ) sin ( n π x 2 b )
z = − h 2
σ 13 = σ 23 = σ 33 = 0
b) load on the bottom surface
σ 13 = σ 23 = 0 , σ 33 = − σ 0 sin ( m π x 1 a ) sin ( n π x 2 b )