“…An orthotropic disk is the one in which the modulus of elasticity, E, and the Poisson's ratio, ν, differ in radial and circumferential directions. The ratio of the modulus of elasticity in one direction to the other is considered as the measure of material orthotropy [15]. Wood is an example of a natural orthotropic material in which material properties in radial and circumferential directions are different [16], [17].…”