γ-irradiation effect on the mechanical properties of in situ specimens made of structural epoxy adhesive and comparison with adhesive bulk behavior

This work examines the effects of γ-irradiation (up to 500kGy) on the mechanical behavior of aluminum in situ specimens bonded with 3MTM Scotch-WeldTM EC-2216 B/A Gray, a commercial two-part epoxy adhesive. Shear tests were performed, from which failure data and incipient axial stiffness were obtained. The results were compared to those of dedicated finite element models that had been tuned with the previously obtained bulk cohesive properties of the adhesive. Analytic models to evaluate stress distribution in the adhesive and joints axial stiffness were applied to validate the developed models and to explain the relatively small stiffness variance (observed both in experimental and numerical analyses results) compared to that of the adhesive Young's modulus. On the whole, the adhesive showed a good tolerance to radiation in the interval studied, as already observed for bulk specimens. Finite element models were found to be accurate in predicting of the stiffness for the entire deformative field, while they overestimated the failure loads and displacements also applying unconservative failure criteria. This is very likely due to the significant number of defects found on the fracture surfaces of bulk specimens.