A modified version of the probabilistic model developed by the authors for damage evolution analysis of laminates subjected to random loading is utilized to predict long-term strength of laminates. The model assumes that each ply in a laminate consists of a large number of mesovolumes. Probabilistic variation functions for mesovolumes stiffnesses as well as strengths are used in the analysis. Stochastic strains are calculated using the lamination theory and random function theory. Deterioration of ply stiffnesses is calculated on the basis of the probabilities of mesovolumes failures using the theory of excursions of random process beyond the limits. Long-term strength and damage accumulation in a Kevlar®/epoxy laminate under tension and complex in-plane loading are investigated. Effects of the mean level and stochastic deviation of loading on damage evolution and time to failure are discussed. It is found that the effect of the deviation in loading is more pronounced at lower mean loading levels. Long-term cumulative damage at the time of the final failure at low loading levels is higher than at high loading levels. The analytical results are qualitatively compared with the available experimental observations.
ASJC Scopus subject areas
- Aerospace Engineering