Impact damage tolerance of composite repairs to highly-loaded, high temperature composite structures

In substantiating the strength of highly-loaded composite structure for aerospace application, consideration must be given to the effect of in-service damage on the residual strength. The same consideration is not given to repaired structure, which may be non-conservative, especially if the aircraft were to have a repair installed early on in the life of type. The current study aims to assess the relative strength reduction in both tension and compression caused by a low energy impact to the original composite structure and to repaired structure in regions of high damage sensitivity.The results of the study showed that the compression after impact strength of the original structure was less than the compression after impact strength of simulated repaired structure, but the tension after impact strength of the repaired structure was reduced. In doing so, the key parameters that govern a critical impact to an external doubler were identified.