Numerical augmentation of the thermography inspection of boron/epoxy bonded repairs

Results from a research program to investigate the use of numerical modeling techniques to predict the results of thermographic inspections of boron/epoxy repairs applied to aluminum structure are summarized. An experimental program was conducted in which non-destructive inspection test articles, representative of typical boron/epoxy repairs of aluminum structure, were developed. Bondline voids were incorporated into the test articles. Numerical models were created to represent the non-destructive inspection standards and the thermal loading of the thermography inspection process. Comparisons were made between the measured thermographic inspection results and the computed results of the numerical models. The comparisons served to validate the modeling process. Once validated, additional models were created to investigate the limitations of thermographic inspections of structure and repair geometries that would be both expensive and unreliable to predict using conventional non-destructive inspection standards.; This investigation indicated that the results of the thermographic inspection of bonded boron/epoxy doublers could be computed using appropriate finite element models. Comparisons of the numerical results with the measured thermographic inspection data established limitations for the modeling process and validated the thermal property data for the repair materials involved. The numerical results generated using the finite element models established acceptable limits for the use of thermography to inspect boron/epoxy repairs. These limits will be useful for both the design and post-installation inspection of such bonded repairs.