Defects and discontinuities in composite laminates cause areas of high stress concentration and reduce the load carrying capacity of the laminate. Tests have shown that a 0.25 inch diameter open hole may reduce the strength properties by more than 50 percent. For this reason, composite material strength is typically evaluated assuming a defect will degrade the material strength properties during service. This assumption creates composite designs that are less weight-optimum but more damage tolerant.
Orthotropic correction factors are available for lamina and laminate material properties to knockdown the properties to an appropriate design value.
Important: The design of damage-tolerant composite structures should be supported by test data.