Browsing by Author "Rowatt, John David"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item A probabilistic model for fatigue damage accumulation in composite laminates(1993) Rowatt, John David; Spanos, Pol D.A stochastic model for the accumulation of fatigue damage in composite laminates is proposed. The model considers the accumulation of fatigue damage as an evolutionary stochastic process and attempts to predict the distribution of damage in terms of the stiffness loss in the laminate as a function of the number of load cycles. The cumulative damage process is modeled as an embedded discrete time, finite state, non-stationary Markov process utilizing a stationary discrete time, finite state, stationary model in conjunction with a time transformation-condensation method. Furthermore, the mechanisms of the complex damage development process in composite laminates are incorporated into the model. This feature affords a more complete and accurate representation of the fatigue damage accumulation process in which the states of the model can be directly related to the stiffness loss in the laminate.Item Application of Markov chains to the critical element model for determining the fatigue life of composites(1995) Rowatt, John David; Spanos, Pol D.A stochastic model for predicting the lifetime of composite laminates subjected to multiaxial fatigue loading is proposed. The model is based on the application of Markov chains to the well known "critical element" model for the fatigue of composite laminates. The model considers the accumulation of fatigue damage as an evolutionary random process characterized by changes in the global compliance of a laminate. These changes are modeled as nonstationary, discrete time, discrete state Markov processes (Markov chains) utilizing stationary Markov chains and polynomial transformations of their indexing parameters. The stationary Markov chains are developed on the assumption of "equivalent damage". Their parameters are determined from experimental data. The Markov chain models yield full cycle dependent probability distributions for the changes in laminate compliance. These changes and their respective distributions are used as input into a mechanical analysis to determine the stresses on the life controlling critical elements of a laminate. The stresses on the critical elements and their derived probability distributions are used in turn to predict the lifetime of a laminate based on Markov chain models of the fatigue behavior of the critical elements. The predictive capability of the proposed model is demonstrated by comparison with experimental results.