Preliminary evaluation of high modulus graphite fiber-resin composites in gas turbine engine hardware has revealed a high degree of residual stresses in such materials. These residual stresses are caused by the mismatch in thermal expansion of the reinforcement and the resin. An analysis indicates that the amount of residual stress can be closely related to the design of the composite construction as well as materials selection and processing. A model was designed for qualitatively evaluating the variables affecting the residual stresses. Several epoxy resin systems were evaluated and characterized for their ability to produce defect-free composites. It was found that resin shrinkage and resin-fiber bonding (transverse tensile strength) are contributors. Recognizing composite residual stresses, an intelligent approach can be taken to composite hardware design.

This content is only available via PDF.