Stress concentrations due to countersunk holes in adhesively bonded bi-layered aluminum subjected to tensile loading

Abstract

The adhesively bonded layered aluminum is used in aircraft structures to avoid knife edge situations when flush head fasteners are used with minimum gage skins. Due to the countersunk hole and adhesive bonding, stress flow becomes more complicated. Extensive knowledge of the different parameters that affect the behavior of the bonded joints with countersunk holes is essential for dependable and effective design. A 3-D finite element model was used to estimate the location and magnitude of stress concentration under remote tension for the aforementioned problem. The influence of the various parameters on stress concentration was investigated for a counter sunk angle of 100º. Different parameters such as ratio of young‟s modulus of adhesive to aluminum, position of adhesive layer, countersunk sunk depths, ratio of thickness to radius and ratio of width to radius have been addressed in this study. The stress flow varies significantly when the plates are filled with fasteners of different pre-tension loads. Also the effects of pre-tension loading were compared for the cases of open hole and fastener filled hole without pre-tension for bonded, monolithic and straight shank hole. The results obtained from the finite element analysis for the monolithic cases have been validated against those reported in literature.