Effect of environment and thermal cycles on tensile behavior ofhybrid single lap joints for fiber metal laminates

This experimental study investigates the effects of sea water and thermal cycling conditions on strength of hybrid lap joints made by fiber metal laminate (FML) and 430 stainless steel adherends subjected to tensile loading. The FMLs are made of three alternative layers of two 430 stainless steel sheets and one prepreg glass fiber reinforced composite (G10) layer. The adherends are bonded by infusion of AD-314 resin mixed with HA-34 hardener and also steel bolt is used for the mechanical fastening to make hybrid single lap joint. The joints are kept in the sea water taken from Persian Gulf for 30 days in the laboratory. Some of the specimens are then thermally cycled for 0, 5 and 10 cycles from 40 to 100 ◦C for the dwell time of 20 min in an oven and from -40 to -100 ◦C for the dwell time of 10 min by liquid nitrogen, and afterwards tested in Tensile loading. One specimen is also tested with 0 thermal cycling at ambient environment for comparison purpose. Experimental results revealed that the bond failure of adhesive in hybrid single lap joint specimens subjected to sea water is 62.75% of the same specimens in the ambient environment and the adhesive strength is improved by 47.34% and 52.16% for 5 and 10 thermal cycling at high temperature and also by 24.76% and 49.5% for 5 and 10 thermal cycling at cryogenic temperatures with respect to sea water at 0 thermal cycling. The ultimate strength of the hybrid lap joint specimens subjected to sea water is 91.3% of the same in ambient environment.

Keywords:

FML , Hybrid joint , Sea water , Tensile test , Thermal cycling , Cryogenic temperature