An Investigation of the Accuracy of FEM Analysis of a Graphite Epoxy Box Beam

A carbon fiber-epoxy wing box was constructed in order to study the behavior of a stressed-skin wing structure with anisotropic sandwich skins. Two wing skins, two spars, and three ribs made up the structure. The spars were designed to act primarily as shear webs so that the bending load in the structure would be reacted mainly by tension and compression in the skins. Linear, buckling, and nonlinear NASTRAN finite element solution sequences were implemented in the analysis of the structure. The structure was loaded as a cantilever beam and strain and deflection measurements were recorded. The finite element nonlinear analysis accurately modeled stiffness, but results for strains at a point were not as accurate.