Date of Award

Fall 1998

Document Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical & Aerospace Engineering


Engineering Mechanics

Committee Director

Ramamurthy Prabhakaran

Committee Member

Stephen Cupschalk

Committee Member

Gene Hou

Committee Member

Zia Razzaq


The development of an approximate analysis for predicting stresses in the skin-stiffener interface region of composite plates and shallow shells is presented. The analysis determines interlaminar normal stress and transverse shear stresses in the direction of the stiffener axial coordinate and the direction of the inplane coordinate perpendicular to the stiffener axis. The analysis accounts for skin-stiffener interfaces with nonzero thickness and for curvature in the skin and stiffener. The interlaminar normal stress and transverse shear stresses at the interface are applied to the lower face of the skin and the upper face of the stiffener flange as unknown functions, and the displacements in the skin and flange are related through the deformation of the interface bond layer. The Rayleigh-Ritz method is used to determine the unknown functions that yield the interlaminar stresses at the skin-stiffener interface. The addition of a failure criterion to the stress prediction capability of the analysis results in the prediction of separation failure. After validation of results from the model, the effects of geometric nonlinearities and aspects of the numerical convergence of the analysis are explored and presented. Furthermore, the influence of various design parameters on the interface stress distribution, and therefore on skin-stiffener separation, is presented.