Merry, Stephanie L.

This thesis presents a method for determining the optimal size and position of stabilizing fins and control surfaces for underwater vehicles. An interactive computer program predicts performance characteristics from calculated vehicle hydrodynamic coefficients. This program merges with a dynamic simulation that utilizes the characteristic coefficients of the design vehicle configuration. Example designs illustrate the procedure and general guidelines for the design of control surfaces. Simulated steady state maneuvers illustrate the performance criteria and confirm the application of the design and simulation software package.

Different methods have been employed to calculate the interlaminar stresses and to study the edge effect in a laminated sandwich specimens under uniaxial tension. However, Finite Element Analysis and Force Balance Method produced stress values which disagreed in both magnitude and sign, a controversy which exists in the case of composite laminates also. Experimental methods, photoelastic coating method and strain gaging, were attempted to obtain the strain distribution on the top surface of a sandwich specimen in three point bending. However, these conventional methods failed to show the sharp strain gradient that exists near the free edge. The Force Balance Method was simplified for sandwich specimens by considering the face laminate as a homogeneous and orthotropic material with averaged properties. Simplified expressions were also obtained for calculating the boundary layer thickness. The boundary layer thickness was found to vary linearly with core thickness for the cases considered.

Debonding failure of cored marine composite materials is investigated. A new test method that subjects the bond line between the core and the face sheets to a shear stress singularity is presented and studied analytically by laminated beam shear deformation theory, numerically by the finite element method, and experimentally with specimens of glass/polyester face sheets on balsa wood or PVC core sandwich beams.