Effect of Stiffener Geometry on the Response of Grid-Stiffened Panels

It is well established that the lateral bending stiffness of thin panels is considerably enhanced by judicious use of ribs or stiffeners. This increase in stiffness is primarily due to a disproportionate increase in the second moment of area, and because relatively little mass is added, stiffened panels are especially appealing in an aerospace engineering context. In experiments it is relatively straightforward to measure bending deflections (especially in a cantilever configuration) and natural frequencies using laser vibrometry and associated signal-processing tools. This paper reports on a parametric study in which bending stiffness and natural frequencies are measured for a set of rectangular panels, conveniently manufactured using a three-dimensional (3D) printer. Both isogrid (stiffeners in a triangular configuration) and orthogrid (stiffeners in a rectangular configuration) structures were made and tested, with certain nondimensional parameters held constant (for example, total mass and length-to-width ratio) to facilitate easier comparison. The boundary condition considered was one edge clamped and the other edges free (simple cantilever) with a consistent plan area aspect ratio, and with the height and arrangement of stiffening ribs providing the major parametric variation.