The introduction of composite materials in aircraft structures is having a profound effect on the design process. These materials permit the designer to tailor material properties to improve structural and aerodynamic performance. In order to obtain maximum benefits, a more integrated multidisciplinary design process is required. Furthermore, because of the complexity of the combined aerodynamic/structural design process numerical optimization methods are required. The present research is focused on a major difficulty associated with the multidisciplinary design optimization process - its enormous computational cost. We consider two approaches for reducing this computational burden: (i) development of efficient methods for cross-sensitivity calculation using perturbation methods; and (ii) the use of approximate numerical optimization procedures. Our efforts are concentrated upon combined aerodynamic-structural optimization. Results are presented for the integrated design of a sailplane wing. The impact of our computational procedures on the computational costs of integrated designs are discussed. / M.S.

Amphibious ships, configured with floodable well decks, present a unique challenge to the Ship Design Team to incorporate maximum troop, cargo and vehicle capacity, along with sufficient well deck size, to facilitate efficient operation of LCAC (Landing Craft Air Cushion) and other amphibious assault craft in support of power projection operations. Analysis of the various LSD 49 Class alternative designs, revealed significant variance in the stability limits for each design. These variations appeared to be directly attributable to wing wall size, as well as to the geometry of the well deck. In order to better understand the effect of these items, and to develop guidelines for future design efforts, this study concentrated on evaluating the stability limitations for various combinations of beam, well deck configuration, and wing wall size using an LSD 49 Class proposed hull form. The results indicated that the most significant parameter affecting the stability of the LSD 49 Class is the height of the well deck above the baseline. The higher the well deck, the smaller the loss of waterplane inertia caused by the entrance of flooding water into the well deck compartment. For lower well decks, the loss of waterplane inertia is more critical at smaller values of beam, but becomes less critical at the upper values of beam considered. In these cases, off-center wing wall flooding becomes more critical, and it is more advantageous to devote larger percentages of beam to the well deck compartment. / M.S.