Initiation and Growth of Transverse Cracks and Edge Delamination in Composite Laminates Part 1. An Energy Method

Abstract

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.