Initiation and growth of delamination in glass/epoxy composites subjected to static and dynamic loading by acoustic emission monitoring

Delamination is one of the most common failure modes of composite materials. It may result from imperfections in the production process or may be caused by service life conditions, such as impact by foreign objects. The presence of delamination in the composite material may reduce the overall stiffness. The geometrical parameters, material proprieties, and loading conditions are important factors which affect the initiation, development and growth of delamination (Chen HP, David L. Comp. Sci. and Technol. 1993; 46:325-33). Experimental results obtained from monotonic tests and instrumented drop tests have shown good agreement between monotonic and dynamic critical load and crack-growth data. Previous studies made on different composite materials (Meraghni F, Benmedakhane S, Benzeggagh ML. In: Poursartip A, Street K, editors. Proc. ICCM 10, vol. I Vancouver, Canada: Woodhead Publishing, 1995:359-66; Barre S, Benzeggagh ML. Comp. Sci. and Technol. 1994; 54:369-76; Benzeggagh ML, Benmedakhene S. Comp. Sci. and Technol. 1995; 55:1-11) have allowed us to set up a schematic model of acoustic emission. In this model the different levels of amplitude signals emitted by materials under different types of loading are assigned to different damage mechanisms. This experimental methodology has been applied to this work and has allowed continuous monitoring of damage growth through delamination tests. This type of analysis has also allowed us to highlight the complementary aspect of acoustic-emission amplitude distributions with microscopic observations. (C) 1999 Elsevier Science Ltd. All rights reserved.