S. Teixeira De Freitas

Temperature effect on the static behaviour of adhesively-bonded metal skin to composite stiffener

The purpose of this research is to study the effect of temperature on the static behavior of an hybrid structure consisting of adhesively bonded Fiber Metal Laminate skin to a composite stiffener. This hybrid structure was tested using stiffener pull-off tests, which is a typical set-up used to simulate the structural behaviour of full-scale components subject to out-of-plane loading. The failure mechanism is very similar at the three temperatures tested: -55C, Room Temperature and +100C. The damage initiates at the central noodle of the composite stiffener. Unstable delamination then propagates from the noodle to the tip of the stiffener foot, preferably through the stiffener foot plies. However, the maximum load and corresponding displacement increase significantly with temperature. At +100C the maximum load increases approximately 15% to 30% when compared to RT. At -55C the maximum load decreases approximately 50% to 60% when compared to RT. No influence of the adhesive was observed in the maximum load values, since no damage occurs at the adhesive bondline. This research identifies that the composite stiffener is the weakest link of the hybrid bonded structure metal-skin-to-composite-stiffener and not the adhesive bondline. This holds for static loading in a wide temperature range.