Design of Hat-Stiffened Composite Panels under Uniaxial Compression and Shear. Minimum Mass Optimization Based on a Simplified Theory

摘要

Literature on stiffened compression panels was reviewed, and a computer program for the evaluation of minimum-mass hat stiffened panels under uniaxial loads was written. In the analytical studies the mechanical properties of the graphite/epoxy material were considered to be linearly elastic and the lower stresses Young's modulus was used. Since a reduction of up to 20% is possible in compression, the 50% mass-saving derived from these results seems too optimistic. A reduced stress-dependent Young's modulus should be used and the tangent modulus theory applied. Better mass-savings are possible with higher hat height values, but these depend on wing airfoil thickness since the optimal distance from the bending neutral axis is required. Under uniaxial compression, a mass-saving up to 40% compared with test data on aluminum panels is evaluated. The fabrication process did not require complex tooling or a difficult production technique. However, complexity could arise for a correct nondestructive inspection of all parts of the panel, because of the closed stiffeners with inclined surfaces.