An improved numerical (finite element) procedure is developed to investigate the stress field in symmetrically laminated composites of finite dimensions. Emphasis is placed on assessing the singular behavior of stresses in regions close to ply-interfaces and the exposed free edge. An accurate evaluation of these stresses will help to better understand the failure process of composite laminates. Mechanical load in the form of uniaxial tension and environmental variables such as temperature and humidity exposures are considered in the formulation. Results tor lam inates under uniaxial tension are presented in this paper; thermal and hygroscopic stresses will be reported in a subsequent paper.

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This paper is concerned with the basic fracture mechanisms involved in matrix-dominated failures in fibrous composite laminates, Specifically, interlaminar fracture in the form of free-edge ply delamination and intra- laminar fracture in the form of multiple transverse cracks are investigated. In each case, a theory is formulated based on the classical linear fracture mechanics concept of strain energy release rate as a criterion for crack growth. A finite element technique incorporating the virtual crack-closure procedure is developed to generate numerical results. Simultaneously, an experimental study is conducted using a series of graphite epoxy laminates in the form of (±25/90 n) s, n = 1,2,3. Part 1 of this paper presents the development of the method from the conceptual, physical and numerical considerations, while Part 2 provides for a comparison between the analyti cal and experimental results.

In part one of this paper, the fracture processes of multiple transverse cracking and free edge delamination in composite laminates have been analyzed by an energy method. Numerical analyses and experimental examination using a series of T300/934 graphite epoxy laminates are pre sented in this part two. While part one is presented in a self-contained form, part two must be regarded as the continuation of part one.

International audienceTheoretical and experimental studies of the free vibrations and the loss of stability of thick-walled cylindrical and spherical shells subjected to external pressure are presented. General equations for the oscillations of the shell under pressure are formulated on the basis of a rigorous theory of finite elasticity. Loss of stability is determined when the fundamental natural frequency of the prestressed shell ceases to be real-valued. Numerical solutions are obtained by solving the specialized equations that are applicable to neo-Hookean materials. Experiments using specimens made of silicone rubber closely verify the theoretical results