Static and fatigue analysis of notched composite laminates

An approach to predict static and fatigue failure of composite laminates with holes is presented. Static failure is predicted when the stress averaged over a characteristic distance is equal to the un-notched failure strength. This averaging distance is determined analytically without the use of additional testing or need for extra material parameters. During fatigue loading, the size of the damage region next to the hole is calculated and the strains at the hole edge are determined. These are used along with the stresses just outside the damage region to determine whether failure starts at the hole edge or the edge of the damage region extends. A previously developed fatigue model based on the cycle-by-cycle probability of failure is used to calculate the number of cycles needed for the residual strain at hole edge or the residual strength at the edge of the damage region to fall below the corresponding applied values. The procedure is repeated until laminate failure. The method is also used to predict cycles to failure for impacted specimens. The predictions are in very good agreement with test results.