Low Cost Composite Modified-Isogrid (Grid-Lock) Construction of Aircraft Structures

A new modified-isogrid construction method, referred to as Grd-Lock, has been previously developed which affords the ability to construct relatively lightweight yet robust and reliable bonded or brazed metallic structures. Isogrid structures rely prmarly on a single skin with integral vertical ribs to furnish the necessary stiffness and strength. Grid-Lock affords the opportunity to acheive superior strength and stiffness at a greatly reduced weight by tying together all of the vertical ribs of an isogrid by means of two attached surface skins. To further ensure intimate contact and excellent load transfer with all internal rib stiffeners, grooves are molded or machined into the surface skins. These grooves provide an efficient shear joint and mechanical interlocking effect. The goal of this study is to develop an efficient all-composite, bonded, Grid-Lock structure. In addition, an assessment of the potential of this construction method to the production of lightweight reliable and cost effective composite aircraft structures will be performed. This will be accomplished through analyical studies aimed at identifying the optimum design configuration for selected part geometries and applied load states. A limited mechanical test effort will be conducted to corroborate analytical predictions.