CHAPTER 2 Macroscopic crack propagation due to stress-corrosion cracking in unidirectional GFRP composites: micromechanical theory and its application H. Sekine Department of Aerospace Engineering, Tohoku University, Japan. Abstract A micromechanical theory of macroscopic crack propagation due to stress-corrosion cracking in unidirectional GFRP composites on the basis of a physically-sound model of crack propagation in a glass fiber is presented. The premise is that a stress-corrosion crack initiates at an inherent surface flaw in a glass fiber, propagates stably with time and finally leads to unstable fracture of the glass fiber. We derive an equation for the macroscopic crack propagation rate as a function of the apparent stress intensity factor for opening mode at the macroscopic crack tip. The theoretical result is in good agreement with experimental data. It is emphasized that the size of the inherent surface flaws affects significantly the macroscopic crack propagation rate. For glass fibers free of inherent surface flaws, the relationship between the macroscopic crack propagation rate and the apparent stress intensity factor can be represented by a simple power law with the value of power of 2. Assuming that the relationship is represented by a simple power law for any size of inherent surface flaws, we obtain the power and coefficient of rate as functions of the size of inherent surface flaws, which are presented in diagrammatic forms. Furthermore, the effect of matrix bridging on the macroscopic crack propagation rate is also discussed. Finally, as an application of the micromechanical theory of macroscopic crack propagation, failure times of GFRP composite structures in corrosive environments are considered. 1 Introduction Glass-fiber-reinforced polymer (GFRP) composites are widely used in corrosive environments because of their superiority over metals or alloys in resisting corrosive attack. Nevertheless, it is known that they can be weakened by the combined influence of stress and corrosive environment [1–12]. Hogg and Hull [13], Noble et al. [14] and Price and Hull [15, 16] studied the actual propagation mechanism of a stress-corrosion crack in individual glass fibers by means of scanning electron microscopy. They observed the fracture surface of each glass fiber to be characterized by a smooth www.witpress.com, ISSN 1755-8336 (on-line) WIT Transactions on State of the Art in Science and Engineering, Vol 21, © 2005 WIT Press doi:10.2495/978-1-85312-669-7/02
Macroscopic crack propagation due to stress-corrosion cracking in unidirectional GFRP composites: micromechanical theory and its application
May 23, 2023
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