Nonlinear Response of Composite Material Structures

Abstract

This paper describes an experimental and a theoretical investigation of structural response of composite, fiber-reinforced materials. The objective of this study is to develop a theoretical model which can predict the response of the composite material based on the behavior of the individual material components. The model is used to predict the response of lam inated, cylindrical models, and the calculated results are compared with experimental data. In the experimental study a number of six-ply cylin drical shells were subject to internal pressure all the way up to failure. The loading was performed in a specially constructed test fixture which per mitted pressurization of the cylinders with a minimum amount of end constraints. The pressure was applied by combustion of a small amount of propellant. The deformation of the specimens was measured in the longi tudinal, the circumferential, and the radial directions and these readings were correlated with the pressure-time history. The experimental results show a pronounced nonlinear response of the cylinders even at relatively small deformations. In order to explain this behavior, a theoretical model was developed, which accounts for large transverse stresses in the plies and permits gradual plastic yield of the matrix material. This model is com bined with finite-element method of stress analysis and it is shown that the experimentally observed nonlinear behavior can be explained by this approach.