This paper presents in detail the application of an energy method to describe a class of delamination crack growth problems found in polymer-based composite laminates. The energy method is derived from the general concepts of classical fracture mechanics. When used judiciously and with proper interpretation of the physical factors pertinent to the crack growth process at the lamina(ply) level, the method describes well delamination growth behavior in laminates that are subjected to monotonically (static) or cyclically(fatigue) applied loads or to both. Both could be in tension or in compression. The basic method can be used to describe not only one-dimensional delamination growth (for example, free edge delamination) but also two-dimensional delamination growth (contoured delamination). Laboratory test results using laminates made of an AS-3501-06 graphite epoxy system are presented along with analytically predicted results. Excellent correlations between analytical and experimental results are obtained.

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A stochastic delamination growth model with parameters written in terms of fracture mechanics, material, and laminate structural parameters is developed for composite laminates subjected to constant amplitude cyclic loading. The model captures the discrete stochastic nature of the delamination growth process in laminated composite materials. Experimental data obtained using AS4/3501-6 coupons with a laminate stacking sequence of [±45/90/0], verifies that the model predicts the mean and variance associated with the delamination growth. Changing only one parameter in the model enables the model to predict delamination growth behavior at several load levels. Two parameters are identified that could possibly expand the model's predictive capability to include laminate geometries other than those used to correlate the model.

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