A progressive damage model for unidirectional fibre-reinforced composites based on fibre fragmentation. Part II: Stiffness reduction in environment sensitive fibres under fatigue

The mechanical behaviour of glass-fibre composites under fatigue or under long term stress is strongly influenced by the stress corrosion cracking of the fibres. In this paper, a stress corrosion model for composite materials reinforced with environment sensitive fibres has been developed and incorporated into a progressive damage model. The model is based on the definition of an effective stress, sigma*(t), which depends on the stress story, that permits the initial failure probability, given by a Weibull distribution, to be used at any later time. This methodology has been incorporated to a thermodynamically consistent constitutive model valid for early fragmentation stages. The model may be used to account for the fibre's behaviour in numerical models based on the rule of mixtures. The ability of the extended progressive damage model to reproduce the stiffness loss of the composite under static or cyclic fatigue loads is demonstrated. (c) 2005 Elsevier Ltd. All rights reserved.