Modified Average Stress Criterion to Predict the Fracture Strength of Various Lay-Ups of Carbon/Epoxy Laminates

The prediction of the fracture strength of carbon/epoxy laminates containing sharp notches through the damage model depends on the un-notched strength and the critical length of the damage zone ahead of the notch. In general, the critical length of the damage zone depends on the material, specimen, and size of the sharp notch. Modifications are made in one of the stress fracture criteria known as the average stress criterion for accurate prediction of notched tensile strength of composite laminates containing sharp notches. To examine the adequacy of these modifications, fracture data of center-cracked carbon/epoxy composite laminates with various lay-ups are considered. The notched strength estimates are found to be close to the test results. The modified average stress criterion is very simple to predict the notched tensile strength.