Investigation of thermoelastic stresses induced at high altitudes on aircraft external fuel tanks

Stephanie Lynn Steber Mousseau, Purdue University

Abstract

As composite technology has grown over the past several decades, the use of composite materials in military applications has become more feasible and widely accepted. Although composite materials provide many benefits, including strength optimization and reduced weight, damage and repair of these materials creates an additional challenge, especially when operating in a marine environment, such as on a carrier deck. This is evident within the Navy, as excessive damage often leads to the scrapping of F/A-18 External Fuel Tanks. This damage comes in many forms, the most elusive of which is delamination. Often the delamination found on the tanks is beyond repairable limits and the cause unknown, making it difficult to predict and prevent. The purpose of this investigation was to study the structure of the Navy's 330 gallon External Fuel Tanks and investigate one potential cause of delamination, stresses induced at high altitudes by cold temperatures. A stress analysis was completed using finite element software, and validation of the model was accomplished through testing of a scale model specimen. Due to the difficulties in modeling and predicting delamination, such as unknown presence of voids and understanding failure criteria, delamination was not modeled in Abaqus, rather stresses were observed and characteristics were studied to understand the potential for delamination within the layup. In addition, studies were performed to understand the effect of material properties and layup sequence on the stress distribution within the tank. Alternative design solutions are presented which could reduce the radial stresses within the tank, and recommendations are made for further study to understand the trade-offs between stress, cost, and manufacturability.

Degree

M.S.A.A.

Advisors

Pipes, Purdue University.

Subject Area

Aerospace engineering

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