Date of Award

2008

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

Advisor

Vincent Caccese

Second Committee Member

Senthil Vel

Third Committee Member

Zhihe Jin

Abstract

The U.S. Navy has a need to build stealthier, faster vessels while at the same time maintaining a high degree of structural integrity. Glass Reinforced Polymers (GRP's) could help achieve this due to their inherent material characteristics. High strength, low weight, corrosion resistance, minimal electromagnetic signature, and elaborate forming capabilities are properties which make GRP's advantageous in marine applications. Previous studies have shown that GRP's alone lack the overall stiffness that is necessary for medium to long length ships, however, a ship with a metallic skeleton and composite outer shell could solve this issue. This type of design would require the incorporation of hybrid composite/metal connections, of which a comprehensive study is needed to ensure that structural failures are avoided. Naval vessels must be able to withstand the random and harsh nature of wave loading, which is why a fatigue response evaluation of any new ship-building design is vital. Special attention must be paid to material connections because this is where failure most often occurs. The U.S. Navy's goal in this research is to accurately assess the fatigue life of hybrid composite/metal connections in their new wave of hull-form constructions. This in turn creates the need to establish sound methods for evaluating fatigue response and environmental effects at connections and interfaces for use in naval vessel design. Experimental testing is essential for this project, however if it can be avoided the potential to save a significant amount of time is apparent. Existing finite element modeling software offers a robust tactic for assessing the structural integrity of proposed hybrid connections. Ansys, a finite element modeling program, was used to mirror the response of two hybrid connection configurations subjected to fully-reversed flexure fatigue loading. A through-the-thickness stress investigation at critical locations in the connection was developed using Ansys. Variables in the hybrid connection were altered in a parametric study and effects on flexibility and stress were observed. Through the use of finite element models, a method for predicting the fatigue life in hybrid joints is proposed.

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