This paper introduces suitable features and methods to define hazard rate function by acoustic emission parameters to develop robust damage statement index and reliability analysis. AE signal energy was first examined to find out relation between damage progress and AE signal energy so that a damage index based on AE signal energy was proposed to quantify progressive damage imposed to composite slabs. Moreover by using AE signal strength, historic index was utilized to develop a modified hazard rate function through integration bathtub curve and Weibull function.