Condition Based Structural Health Monitoring and Prognosis of Composite Structures under Uniaxial and Biaxial Loading

This paper presents a condition based structural health monitoring (SHM) and prognosis approach to estimate the residual useful life (RUL) of composite specimens in real time. On-line damage states, which are estimated using real time sensing information, are fed to an off-line predictive model to update future damage states and RUL. The on-line damage index or damage state at any given fatigue cycle is estimated using correlation analysis. Based on the on-line information of the previous and current damage states, an off-line model is developed to predict the future damage state and estimate the RUL. The off-line model is a stochastic model which is developed based on the Gaussian process approach. In this paper, the condition based prognosis model is used to estimate the cumulative fatigue damage in composite test structures under constant amplitude fatigue loading. The proposed procedure is validated under uniaxial fatigue loading as well as biaxial fatigue loading. Experimental validations demonstrate that the prediction capability of the prognosis algorithm is effective in predicting the RUL under complex stress states.