The effects of stress concentrations on the fatigue life of fiber-reinforced graphite epoxy composites play a very important role in the aerospace industry. Primarily stress concentrations refer to the holes. However, fasteners are the primary manufacturing process for attachment of graphite epoxy panels in use in the aerospace industry today. These conditions of composites with and without fasteners greatly affect the fatigue properties of such panels.
In an attempt to understand the stress field created by fasteners in carbon-reinforced graphite composites, and how these stress fields affect the fatigue life of these composites, a fatigue life analysis program was conducted. It compared specimens with machined fastener holes and specimens with fasteners placed in them. In addition to the fatigue analysis performed on the specimens, photoelastic stress analysis is used to determine the stress field created from the use of fasteners. The difference in stress fields of specimens without fasteners compared to specimens with fasteners can be determined to allow designers to prolong the fatigue life of composites.